Patent Publication Number: US-7913340-B2

Title: Method of controlling motor-driven washing machine and control system for the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of application Ser. No. 10/486,330, filed Feb. 10, 2004 now abandoned, which is the 35 U.S.C. §371 National Stage entry of International Application No. PCT/KR03/00960, filed May 15, 2003, and claims the benefit of Korean Application No. P2002-26886 filed on May 15, 2002, Korean Application No. P2002-27127 filed on May 16, 2002, Korean Application No. P2002-27132 filed on May 16, 2002, Korean Application No. P-2002-40211 filed on Jul. 11, 2002, Korean Application No. P2002-40292 filed on Jul. 11, 2002, Korean Application No. P2002-44687 filed on Jul. 29, 2002, Korean Application No. P2002-73580 filed on Nov. 25, 2002, Korean Application No. P2002-73898 filed on Nov. 26, 2002, Korean Application No. P2002-74052 filed on Nov. 26, 2002 and Korean Application No. P2002-75054 filed Nov. 26, 2002, all of which are hereby incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a washing machine, and more particularly, to a method of controlling a motor-driven washing machine and a control system for the same. 
     2. Discussion of the Related Art 
     Motor-driven automatic washing machines are common these days. A typical washing machine may include a motor for driving an agitator and a rotatable tub severing both as a wash tub and a dehydration tub and the motor is coupled to a drive shaft. During a typical wash or rinse cycle, the motor is caused to rotate back and forth to agitate the clothes and water in the wash tub for cleaning or rinsing of the clothes. 
     In addition, during a spin cycle, the motor spins the wash tub containing a load of wet clothes to be dehydrated to remove water from the wet clothes by centrifugal force. Because the wash tub rotates at a very high speed, many problems can occur. For example, if the operation of the motor is not stopped properly when a user mistakenly opens a washer door and sticks a hand into inside of the tub, the user may be seriously harmed. The user should be advised of such error promptly so that the error of the motor or any other components that associates with the motor can be quickly fixed. 
     In another example, when a control for braking a motor in motion during a spin cycle is not properly done, the motor-clutch mechanism may generates a noise and the mechanism can be damaged due to the motion of the heavy wash tub at a high speed. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed to a method of controlling a motor-driven washing machine and a control system for the same that substantially obviate one or more problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same that prevent a motor-clutch mechanism from generating a noise and being damaged. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same, in which a proper control can be achieved even if an initial algorithm for braking a motor is not executed properly. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same in which, malfunction of a motor during a motor interruption is determined and a corresponding error message is displayed for warning a user of the malfunction. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine that performs a motor interruption based on the weight of a load of clothes to be washed or dehydrated. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same that prevent a motor from being damaged due to reverse voltages generated by the motor during motor-brake operation. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same, in which malfunction of a braking resistor is detected and motor operation is stopped for avoiding any motor damage. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same that minimize the time it takes to reduce the motor speed. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same, in which a washer door is locked only when the speed of a motor reaches a predetermined speed. 
     Another object of the present invention is to provide a method of controlling a motor-driven washing machine and a control system for the same that prevent the motor from being damaged during a spin cycle. 
     A further object of the present invention is to provide a circuit for limiting a motor current in an electrical appliance that the value of the limiting current can be varied. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of controlling a motor-driven washing machine includes the steps of generating an interruption command for braking a motor in motion during a wash cycle; applying a first phase-reversed voltage to a voltage input terminal of the motor in motion, the first phase-reversed voltage corresponding to a first current speed of the motor; and electrically shorting the voltage input terminal of the motor for a predetermined period of time if a second phase-reversed voltage is higher than or equal to a critical voltage level, the second phase-reversed voltage corresponding to a second current speed of the motor. 
     In another aspect of the present invention, a control system for a washing machine includes a motor rotating at least one of a washing tub and an agitator provided in the washing machine in a wash cycle; a motor brake unit initially applying a first phase-reversed voltage to a voltage input terminal of the motor when an interruption command for braking the motor in motion is generated during the wash cycle, the first phase-reversed voltage corresponding a first current speed of the motor in motion, and a controller measuring a second current speed of the motor and generating a control signal if a second phase-reversed voltage is higher than or equal to a critical voltage level, the second phase-reversed voltage corresponding to the second current speed of the motor, wherein the motor brake unit electrically shorts the voltage input terminal of the motor upon receiving the control signal from the controller. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine having a load controller includes the steps of initiating a wash cycle by operating a plurality of load units including a motor according to a wash option selected by a user; transmitting a brake control signal to the load controller if an opening of a washer door provided in the washing machine is detected, the load controller executing a load-brake algorithm to brake operations of the plurality of load units in response to the brake control signal; determining whether the load-brake algorithm is properly executed by the load controller by communicating with the load controller; and transmitting control signals directly to the plurality of the load units so as to brake the operations of the plurality of the load units if the load-brake algorithm is properly executed by the load controller. 
     In another aspect of the present invention, a control system for a washing machine includes a door sensor detecting an opening of a washer door provided in the washing machine; a load controller coupled to the door sensor for executing a load-brake algorithm to brake operations of a plurality of load units of the washing machine when the opening of the washer door is detected by the door sensor; a main controller transmitting control signals directly to the plurality of load units so as to brake the operations of the plurality of load units if the load-brake algorithm is not properly executed by the load controller. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of initiating a wash cycle by operating a motor provided in the washing machine according to a washing option selected by a user; generating a motor-brake signal to brake the operation of the motor when a motor-interruption command is generated and measuring a brake period which represents a total length of time it takes to completely stop the operation of the motor; determining malfunction of the motor based on whether the measured brake period exceeds a predetermined period of time; and displaying a warning message on a display unit, the message indicating the determined malfunction of the motor. 
     In another aspect of the present invention, a control system for a washing machine includes a motor rotating a washing tub or an agitator provided in the washing machine according to a washing option selected by a user; a microprocessor operatively coupled to the motor for braking operation of the motor when a motor-interruption command is generated and measuring a brake period which represents a total length of time it takes to completely stop the operation of the motor, the microprocessor determining malfunction of the motor based on whether the measured brake period exceeds a predetermined period of time; and a display unit displaying a warning message indicating the determined malfunction of the motor upon receiving a control signal from the microprocessor. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of increasing a speed of a motor from zero to a first predetermined speed W 1  to initiate a spin cycle, during which the motor rotates a washing tub containing a load of clothes to be dehydrated; reducing the motor speed from W 1  to a second predetermined speed W 2  and measuring a deceleration period that it takes to reduce the motor speed from W 1  to W 2 ; increasing the motor speed from W 2  to a third predetermined speed W 3 ; braking the motor according to a slow brake logic if a first interruption of the motor is ordered during the step of increasing the motor speed from W 2  to W 3 ; increasing the motor speed from W 3  to a fourth predetermined speed W 4 ; and selecting one of plurality of rapid-brake logics on the basis of the measured deceleration period and braking the motor according to the selected rapid-brake logic if a second interruption of the motor is ordered during the step of increasing the motor speed from W 3  to W 4 . 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of applying a phase-reversed voltage to a voltage terminal of a motor in motion to brake the motor when a motor-interruption command is generated during a wash or spin cycle, the motor generating a reverse voltage and a reverse current when being braked; initially reducing the reverse voltage generated by the motor by allowing the reverse current to flow through a braking resistor connected to the motor if the reverse voltage is higher than a predetermined voltage level; determining malfunction of the braking resistor on the basis of an actual current-flow period of the braking resistor; and electrically shorting the voltage terminal of the motor for a predetermined period of time if the malfunction of the braking resistor is determined. 
     In another aspect of the present invention, a control system for a washing machine includes a motor rotating a washing tub or an agitator provided in the washing machine in a wash or spin cycle; a motor driving unit applying a phase-reversed voltage to a voltage terminal of the motor in motion if a motor-interruption command is generated, the motor generating a reverse voltage and a reverse current when the phase-reversed voltage is applied; a braking resistor connected to the motor; and a microprocessor initially reducing the reverse voltage generated by the motor by allowing the reverse current to flow through the braking resistor if the reverse voltage is higher than a predetermined voltage level, the microprocessor electrically shorting the voltage terminal of the motor for a predetermined period of time if it determines malfunction of the braking resistor on the basis of an actual current-flow period of the braking resistor. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of determining whether a current DC voltage of a driving unit driving a motor is less than or equal to a predetermined voltage level for each predetermined period; measuring a current leading phase angle of the current DC voltage if the current voltage is less than or equal to the predetermined voltage level; and decreasing the current leading phase angle of the current DC voltage by a first predetermined level if the measured leading phase angle is greater than zero. 
     In another aspect of the present invention, a control system for a motor-driven washing machine includes an electrical motor; a driving unit that applies an input voltage to the motor to drive the motor; a voltmeter that measures a reverse voltage generated by the motor for each predetermined period; and a microprocessor reducing a speed of the motor if the measured reverse voltage is less than or equal to a predetermined voltage level. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of determining whether a command for a spin cycle is received from a user; and locking a washer door on the basis of whether a speed of a motor reaches a first predetermined speed if the spin cycle command is received, the motor rotating a washing tub containing a load of clothes to be dehydrated. The step of locking the washer door includes increasing the motor speed from zero to the first predetermined speed to initiate the spin cycle; and generating a control signal to a door locking unit if the motor speed is equal to the first predetermined speed, the door locking unit locking the washer door upon receiving the control signal. 
     In another aspect of the present invention, a control system for a washing machine includes a washing tub containing a load of clothes to be dehydrated; an electrical motor rotating the washing tub if a command for a spin cycle is received from a user; and a microprocessor locking a washer door on the basis of whether a speed of the motor reaches a first predetermined speed. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of determining whether a first current speed of a motor is less than a first predetermined speed if a motor-interruption of the motor is generated during a spin cycle, the motor rotating a washing tub containing a load of clothes to be dehydrated during the spin cycle; and braking the motor in motion by shorting power terminals of the motor for a first predetermined period if the first current speed is less than the first predetermined speed. The method further includes the steps of applying phase-reversed voltages to the power terminals for a second predetermined period if a second current speed of the motor is less than the first predetermined speed and greater than a second predetermined speed; and allowing a braking resistor connected to the motor to flow reverse currents generated by the motor so as to dissipate electrical power into heat if the second current speed of the motor is less than the first predetermined speed and greater than the second predetermined speed. 
     In another aspect of the present invention, a control system for a washing machine includes a washing tub containing a load of clothes to be dehydrated; a motor rotating to the washing tub during a spin cycle; and a microprocessor braking the motor shorting power terminals of the motor if a motor-interruption is generated during the spin cycle and if a first current speed of the motor is less than a first predetermined speed. 
     In another aspect of the present invention, a circuit for limiting a motor current in an electrical appliance includes a first resistor and a dip switch connected between a power source and a ground in series, the dip switch comprising a plurality of resistors having different resistances; a capacitor connected to the dip switch in parallel; an op amplifier having an inverting input connected to a node between the first resistor and the dip switch; and a third resistor connected between an noninverting input of the op amplifier and a ground, wherein any one of the plurality of resistors of the dip switch can be conveniently selected for limiting a current that flows through the third resistor. 
     In another aspect of the present invention, a method of controlling a motor-driven washing machine includes the steps of measuring a voltage of a node between the transistor and the braking resistor; displaying a warning message indicating that the brake resistor is in an inoperative condition if the measured voltage is equal to zero; repeating the step of determining if a command for a wash cycle is received; and initiating the wash cycle if the measured voltage of the node is not equal to zero. 
     In another aspect of the present invention, a control system for a washing machine includes a motor rotating a wash tub or an agitator of the washing machine; a driving unit that drives the motor by applying input voltages to the motor; a pair of a braking resistor and a transistor connected to the driving unit in parallel, the transistor being connected to the braking resistor in series; a voltmeter measuring a voltage of a node between the transistor and the braking resistor; and a microprocessor generating a warning signal if the measured voltage of the node is not equal to zero. 
     It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; 
         FIG. 1A  illustrates a control system that drives a motor provided in a washer according to a first embodiment of the present invention; 
         FIG. 1B  illustrates the detailed structures of the motor brake unit  60 , the transformer  50  and the motor  81  shown in  FIG. 1A ; 
         FIG. 1C  illustrates a current flow (L 1 ) of the motor brake unit  60  when the phase-shifted voltage applied to the motor brake unit  60  is less than V c ; 
         FIG. 1D  illustrates a method of controlling a motor provided in a washer according to the first embodiment of the present invention; 
         FIG. 2A  illustrates an apparatus of controlling load units (e.g., a motor) in a washer according to a second embodiment of the present invention; 
         FIG. 2B  illustrates a method of controlling load units in a washer according to the second embodiment of the present invention; 
         FIG. 3A  illustrates an apparatus of detecting malfunction of a motor in a washer according to a third embodiment of the present invention; 
         FIG. 3B  illustrates a method of detecting malfunction of a motor in a washer according to the third embodiment of the present invention; 
         FIG. 4A  and  FIG. 4B  illustrate a method of interrupting (braking) operation of a motor in a washer according to a fourth embodiment of the present invention; 
         FIG. 5A  illustrates a control system that drives a motor provided in a washer according to a fifth embodiment of the present invention; 
         FIG. 5B  illustrates a method of controlling a motor in a washer according to the fifth embodiment of the present invention; 
         FIG. 6A  illustrates a control system that drives a motor provided in a washer according to a sixth embodiment of the present invention; 
         FIG. 6B  illustrates a method of controlling a motor in a washer according to the sixth embodiment of the present invention; 
         FIG. 7A  illustrates a control system controlling a motor in a washer according to a seventh embodiment of the present invention; 
         FIG. 7B  illustrates a method of controlling a motor in a washer according to the seventh embodiment of the present invention; 
         FIG. 8A  illustrates an apparatus of controlling operation of a motor in a washer according to an eighth embodiment of the present invention; 
         FIG. 8B  illustrates a method of controlling operation of a motor in a washer according to the eighth embodiment of the present invention; 
         FIG. 9A  illustrates a control system that drives a motor provided in a washer according to a ninth embodiment of the present invention; 
         FIG. 9B  illustrates a method of controlling a motor in a washer according to the ninth embodiment of the present invention; and 
         FIG. 10  illustrates a circuitry for limiting a motor current in an electrical appliance according to a tenth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Embodiment (1) 
       FIG. 1A  illustrates a control system that drives a motor provided in a washer according to a first embodiment of the present invention. Referring to  FIG. 1A , the control system includes a power supply unit  40  rectifying and/or smoothing an AC power voltage generated by a power source, a transformer  50  having a converter (not illustrated) and for converting the rectified AC voltage into a DC voltage and a capacitor (not illustrated) for storing the converted DC voltage, a motor  81  rotating a tub and/or an agitator provided in the washer, a motor brake unit  60  braking the operation of the motor  81  by applying an input voltage to the motor  81  upon receiving a brake control signal, and a controller  70  measuring the DC voltage stored by the transformer  50  and generating the brake control signal to the motor brake unit  60 . 
     The DC voltage stored in the capacitor of the transformer  50  is used for driving the motor  81 , and the motor  81  transmits the dynamic energy to a clutch (not illustrated) that engages with the tub and/or agitator provided in the washer for washing a load of clothes to be washed. When a user inputs a command for interrupting (braking) the motor operation by turning the power of the washer off, opening a washer door, or manually touching a key control panel, the controller  70  generates a motor interruption signal to the motor brake unit  60 . In addition, the controller  70  continuously monitors the speed of the motor  81  and outputs the motor speed information to the transformer  50 , which then applies a voltage corresponding to the motor speed to the motor brake unit  60 . 
     The motor brake unit  60  shifts the phase of the voltage outputted by the transformer  50  by 180 degrees and applies the phase-shifted voltage (phase-reversed voltage) to the motor  81  so as to brake the motor operation. However, when a phase-shifted voltage corresponding to a speed value higher than a certain motor speed is applied to the motor  81 , a noise may be generated in the motor-clutch mechanism and the mechanism may be damaged. This is because the actual rotational displacement of the clutch is greater than the rotational displacement of the motor  81  due to the rotational speed difference between the motor  81  and the clutch. For this reason, the controller  70  initially stores a critical phase-shift voltage Vc that starts to generate the noise in the motor-clutch mechanism and that may damage the mechanism, and it performs a motor brake by shorting the power input terminals of the motor  81  if the current phase-reversed voltage is greater than V c . 
       FIG. 1B  illustrates the detailed structures of the motor brake unit  60 , the transformer  50  and the motor  81  shown in  FIG. 1A . As shown in  FIG. 1B , the motor brake unit  60  comprises three pairs of insulated gate bipolar transistors (hereinafter, “transistor”) connected in parallel, where each pair comprises two transistors connected in series. A diode (D 1  to D 6 ) is connected to each transistor, which can be shorted by the diode. Transistors T 2 , T 4  and T 6 , which are directly connected to three winded wires of the motor  81 , apply the voltage supplied by the transformer to the winded wires of the motor  81 , respectively, for operating or braking the motor  81 . 
       FIG. 1C  illustrates a current flow (L 1 ) of the motor brake unit  60  when the phase-shifted voltage applied to the motor brake unit  60  is less than V c . On the other hand, a current flow (L 2 ) of the motor brake unit  60  when the phase-shifted voltage is greater than or equal to V c . In other words, if the controller  70  determines that the voltage being inputted to motor brake unit  60  is greater than or equal to V c , the motor brake unit  60  shorts the input terminals of the motor  81  as shown in  FIG. 1B  for a predetermined period of time (e.g., 0.5 sec). As shown in  FIG. 1B , the connections between the transformer  50  and the motor  81  are shorted by activating T 2 , T 4  and T 6  and D 2 , D 4  and D 6  and by deactivating T 1 , T 3 , and T 5 . Therefore, the voltage of the transformer  50  is not applied, but instead, the voltage previously applied to the winded wires  85  of the motor  81  are consumed for braking the motor operation. After the input terminals of the motor  81  are shorted for 0.5 sec, the speed of the motor  81  is reduced and the reduced motor speed is transmitted to the controller  70 , which then applies a voltage corresponding to the reduced motor speed to the motor driving unit  60  so that the motor  81  can be stopped without generating any noise in the motor-clutch mechanism. 
     Reference will now be made in detail to a method of controlling a motor provided in a washer according to the first embodiment of the present invention, which is illustrated in  FIG. 1D . Initially, a user inputs a command for interrupting (braking) the motor operation by turning the power of the washer off, opening a washer door, or manually touching a key input panel (SS 1 ). Next, the controller  70  controls the transformer  50  to apply a voltage corresponding to the current motor speed to the motor brake unit  60 , which then performs a motor brake by shifting the phase of the voltage by 180 degrees and applying the phase-shifted voltage (phase-reversed voltage) to the motor  81  (S 2 ). Thereafter, the controller  70  measures the current speed of the motor  81  again and compares the voltage corresponding to the measured motor speed with a critical phase-shift voltage Vc (S 3 ), which is previously stored by the controller and represents a value of the phase-shifted voltage that causes the motor-clutch mechanism to generate a noise if applied to the motor  81 . 
     If the voltage corresponding to the current motor speed is less than Vc, steps S 2  and S 3  are repeated again. On the other hand, if the voltage is greater than or equal to Vc, the controller  70  performs a motor brake by shoring the power input terminals of the motor  81  for a predetermined period of time T (e.g., 0.5 sec) so that the voltage corresponding the current motor speed is not applied to the motor  81 . Next, if the controller  70  determines that the operation of the motor  81  is stopped (S 5 ), it terminates the motor brake algorithm. Otherwise, steps S 1  to S 5  are repeated until the motor operation is stopped. 
     Embodiment (2) 
       FIG. 2A  illustrates an apparatus of controlling load units (e.g., a motor) in a washer according to a second embodiment of the present invention. Referring to  FIG. 2A , the apparatus includes a key input unit  210  receiving commands from a user for a wash cycle, a door sensor  240  for sensing opening of a washer door of the washer, and a load controller  230  that executes an interrupt program or algorithm for interrupting operations of load units  260  upon receiving a signal indicating the opening of the washer door, where the load units  260  include a motor rotating a tub and/or an agitator provided in the washer, a water supply system supplying water to the tub, and a drain system draining water from the tub. The apparatus shown in  FIG. 2A  further includes a main controller  220  that generates control signals to initiate the wash cycle according to the user&#39;s commands and controls the operations of the load units based upon whether the interrupt program is properly executed by the load controller  230 . The apparatus further includes a memory  250  (e.g., EEPROM) for storing a plurality of parameter values that correspond to various washing options and a display unit  270 , such as an LCD display, that displays information indicating the opening of the washer door upon receiving a control signal from the main controller  220 . 
     When a user inputs commands for a wash cycle through the key input unit  210 , the main controller  220  transmits the commands to the load controller  230 . Then the load controller  230  performs a wash cycle by driving the load units  260  according to the received commands. The load units  260  include a motor rotating a tub, and it may further include a water supply supplying water to the tub and a drain draining water from the tub. 
     When the door sensor  240  detects or senses opening of a washer door, it sends a signal indicating the opening of the washer door to the load controller  230  and the main controller  220 . Thereafter, the load controller  230  runs an interrupt program (e.g., executing an interrupt algorithm) for interrupting or suspending operations of the load units  260 . The main controller  220  determines whether the load controller  230  has executed the interrupt program properly. If the main controller  220  determines that the load controller  230  has not executed the program properly, it generates a direct control signal to the load units  260  for properly interrupting or suspending the operations of the load units  260 . For example, the load controller  230  periodically transmits speed (RPM) information of a motor which is operatively coupled to the load controller  30  so that the main controller  220  can determine whether the load controller  230  has executed the interrupt program properly by monitoring the speed information of the motor. 
     Reference will now be made in detail to a method of controlling load units in a washer according to the second embodiment of the present invention, which is illustrated in  FIG. 2B . Referring to  FIG. 2B , the main controller  220  initially generates control signals to initiate a wash cycle according to a washing option selected by a user (S 211 ). If the main controller  220  detects opening of a washer door during the wash cycle (S 212 ), it determines whether the load controller  230  has executed an interruption program (e.g., an interrupt algorithm) properly by receiving operation data of the load units  260  from the load controller  230  via a data communication line, such as a serial communication line, and by monitoring the received operation data (S 213 ). If it is determined in step S 213  that an interruption program is properly executed by the load controller  230 , then the main controller  220  allows the load controller to interrupt the operations of the load units  260  (S 214 ). On the other hand, if the interrupt program is not properly executed, the main controller  220  sends direct control signals to the load units  260  for interrupting the operations of the load units  260  (S 215 ). One of the advantages of controlling the load units of a washer according to the second embodiment described above is that a reliable control for interrupting operations of the load units is still achieved even when any error occurs in interrupting the operations of the load units by the load units. 
     Embodiment (3) 
       FIG. 3A  illustrates an apparatus of detecting malfunction of a motor in a washer according to a third embodiment of the present invention. Referring to  FIG. 3A , the apparatus includes a key input unit  310  receiving commands from a user for a wash cycle, a motor  340  rotating a tub and/or an agitator in the washer, a speed measuring unit  330  measuring the speed of the motor  340 , and a counter  320  that measures interruption periods of the motor  340 . An interruption period of the motor  340  represents a period of time that it takes for the motor  340  to completely stop since an interruption command is inputted by the user through the key input unit  310  or opening of a washer door (not illustrated) of the washer is detected. The apparatus shown in  FIG. 3A  further includes a memory  370  (e.g., EEPROM) that stores the measured interruption period of the motor  340  if the measured period is greater than a predetermined length of time, a microprocessor  360  that determines malfunction of the motor  340  based upon whether a total number of the stored interruption periods, which are greater than the predetermined length of time, is greater than a threshold frequency, and a display unit  350  (e.g., an LCD) that indicates the malfunction of the motor  340  upon receiving a control signal from the microprocessor  360 . 
     When the microprocessor  360  receives an interruption command from the user through the key input unit  310  or detects opening of a washer door of the washer, it generates an interruption signal to the motor  340  to interrupt or stop operation of the motor  340 . Thereafter, the counter  320  measures an interruption period of the motor  340 , which represents a period of time it takes for the motor  340  to completely stop since the interruption signal is generated by the microprocessor  360 , and the microprocessor stores the measured interruption period in the memory  370  if the measured period is greater than a predetermined length of time. Next, the microprocessor  360  determines whether a total number of the interruption periods stored in the memory  370  is greater than a threshold frequency. If the total number of periods is determined to be the threshold frequency, the microprocessor  360  sends a control signal to the display unit  350  to display a message indicating malfunction of the motor  340  to the user. 
     Reference will now be made in detail to a method of detecting malfunction of a motor in a washer according to the third embodiment of the present invention, which is illustrated in  FIG. 3B . Referring to  FIG. 3B , when power is supplied to a washer (S 31 ) and the microprocessor  360  determines that a command for initiating a wash cycle is received from the user through the key input unit  310  (S 32 ), the microprocessor  360  initiates the wash cycle according to a wash option selected by the user (S 33 ). Thereafter, when the microprocessor  360  determines that an interruption command is received from the user through the key input unit  310  or opening of a washer door of the washer is detected (S 34 ), it generates an interruption signal to interrupt or stop operation of the motor  340  and measures an interruption period of the motor  340  using the counter  320  (S 36 ). The interruption period of the motor  340  represents a period of time it takes to completely stop the operation of the motor  360  since the interruption signal is generated. On the other hand, if it is determined in step S 34  that no interruption command is received from the user and the opening of the washer door is not detected, the microprocessor  360  continues the wash cycle (S 35 ). 
     Referring back to  FIG. 3B , after the interruption period of the motor  340  is measured in step S 36 , the microprocessor  360  determines whether the measured interruption period is greater than a predetermined length of time T predetermined  (S 37 ). If it is, it stores the measured interruption period in the memory  370  (S 38 ), and otherwise, it finishes interrupting the operation of the motor  340  (S 41 ). Next, the microprocessor  360  further determines whether a total number of the interruption periods, which are stored in the memory  370  up to the present time, is greater than a threshold frequency value N predetermined  (S 39 ). If the total number of periods is determined to be greater than the threshold frequency value in step S 39 , the microprocessor  360  sends a display control signal to the display unit  350  to display a message indicating malfunction of the motor  340  to the user (S 40 ). Using the apparatus and method according to the third embodiment of the present invention, a user can easily and conveniently be notified of malfunction of the motor  340  when the operation of the motor is not completely stopped within a predetermined length of time upon receiving an interruption command from the microprocessor  360 . Therefore, the user can repair the motor in advance without damaging the motor or any other component of the washer. 
     Embodiment (4) 
       FIG. 4  illustrates a method of interrupting (braking) operation of a motor in a washer according to a fourth embodiment of the present invention. The washer includes a motor rotating a tub or an agitator, a microprocessor generating control signals to control operation of the motor. Referring to  FIG. 4 , the microprocessor of the washer initially increases the speed of the motor W (S 411 ). When W is determined to be greater or equal to a first predetermined speed W 1  (S 412 ), the microprocessor turns the motor power off (S 413 ). On the other hand, if W is determined to be less than W 1  in step S 412  and if interruption of the motor operation is ordered (S 414 ), the microprocessor interrupts (brakes) the motor operation based on a slow-brake logic (S 415 ). The interruption of the motor operation gets ordered when a user inputs a command for interrupting (braking) the motor operation by turning the power of the washer off, opening a washer door, or manually touching a key control panel. 
     After the motor power is turned off in step S 413 , power-free rotation of the motor occurs and thereby W gradually decreases (S 416 ). If the microprocessor determines that the microprocessor determines whether W is less than or equal to a second predetermined speed W 2  being less than W 1  (S 417 ), it determines the weight of a load of clothes being contained in the tub by measuring T that represents a length of time that it takes for W to decrease from W 1  to W 2  (S 418 ). On the other hand, if W is determined to be still greater than W 2  in step S 417  and if interruption of the motor operation is ordered (S 419 ), step S 415  is repeated. 
     After the load weight is determined in step S 418 , the microprocessor increases W (S 420 ). If W is determined to be greater than or equal to a third predetermined speed W 3  which is greater than W 1  (S 421 ), the microprocessor further increases W (S 423 ). On the other hand, if W is determined to be less than W 3  in step S 421  and if interruption of the motor operation is ordered (S 422 ), step S 415  is repeated. Referring back to step S 423 , if W is determined to be greater than or equal to a fourth predetermined speed W 4  which is greater than W 3  (S 424 ), the microprocessor maintains the motor speed to W 4  and performs a spin cycle (S 425 ). 
     If W is determined to be less than W 4  in step S 424  and if interruption of the motor operation is ordered (S 426 ), the microprocessor selects one of a plurality of rapid-brake logics on the basis of T measured in step S 418  and interrupts or brakes the motor operation according to the selected rapid-brake logic (S 427 -S 432 ). For example, if T is determined to be less than or equal to a first predetermined length of time T 1  (S 427 ), the microprocessor brakes the motor operation based on a first rapid-brake logic (S 428 ). And if T is determined to be greater than T 1  but less than or equal to a second predetermined length of time T 2  (S 429 ), the motor operation is interrupted based on a second rapid-brake logic (S 430 ). In other words, if T is determined to be greater than an (n−1)th predetermined length of time T n−1  but less than or equal to an nth predetermined length of time T n  where n=2, 3, 4, . . . N (S 431 ), the microprocessor brakes the motor operation based on an nth rapid-brake logic (S 432 ). 
     Referring back to step S 425 , if a spin period, during which W 4  is maintained, is determined to be greater than or equal to a predetermined period of time E (S 433 ), the microprocessor turns off the motor power (S 434 ). On the other hand, if the spin period is determined to be less than E in step S 433  and if interruption of the motor operation is ordered (S 435 ), the microprocessor selects on of the plurality of rapid-brake logics on the basis of T measured in step S 428  and interrupts the motor operation according to the selected rapid-brake logic (S 427 -S 432 ). After the motor power is turned off in step S 434 , if the microprocessor determines in step S 436  that W is less than or equal to W 3  and if interruption of the motor operation is ordered (S 438 ), step  415  is repeated. In addition, if W is determined to be greater than W 3  in step S 436  and if interruption of the motor operation is ordered (S 437 ), steps S 427  to S 432  are repeated. 
     In the method of interrupting operation of the washer motor shown in  FIG. 4 , an appropriate motor brake logic is selected based on the weight of the load of clothes so that the optimal interruption of the motor operation can be achieved while avoiding any damage on the motor or any other components that associate with the motor. 
     Embodiment (5) 
       FIG. 5A  illustrates a control system that drives a motor provided in a washer according to a fifth embodiment of the present invention. Referring to  FIG. 5A , the control system includes a transformer  54  having a converter  54 A and a first capacitor C 1  for converting the AC power generated by the AC power source  52  into DC power, a switch  52 A connecting or disconnecting the AC power source  52  to the transformer  54 , and a switching mode power supply (SMPS) unit  56  transforming the DC voltage converted by the transformer  54  into a voltage having a predetermined level. 
     The motor control system shown in  FIG. 5A  further includes a relay unit  56 A which is connected between the SMPS unit  56  and the AC power source  52  and cuts off the AC power if its frequency is higher than a predetermined frequency value, a first resistor R 1  connected to the relay unit  56 A in parallel, a motor  51  rotating a tub or an agitator in the washer, a driving circuit  58  driving the motor  51  by supplying the voltage converted by the SMPA unit  56  to the motor  51 , a microprocessor  59  controlling operation of the motor  51 , an insulated gate bipolar transistor (IGBT)  57  performing pulse width modulation upon receiving a control signal from the microprocessor  59 , a voltage comparator  53  comparing the reverse voltage generated by the motor  51  during a motor brake with a predetermined voltage value, and a braking resistor  55  dissipating the reverse voltage generated by the motor  51  into heat so as to prevent possible circuit damages due to the reverse voltage. 
     Reference will now be made in detail to a method of controlling a motor in a washer according to the fifth embodiment of the present invention, which is illustrated in  FIG. 5B . Referring to  FIG. 5B , when the microprocessor  59  determines that any one of the conditions for braking operation of the motor  51  is met, it sends interruption signals to the motor driving circuit  58 , which then applies phase-reversed input voltages to the motor  51  (S 511 ). In step S 511 , the reverse voltages are then generated by the motor  51  due to its rotation and they are applied to the driving circuit  58 . In a case where the motor  51  is driven by three input voltages having three different phases, the reverse voltages generated by the motor  51  during the motor brake also have three phases. Therefore, the phases of the reverse voltages depend on the phases of the input voltages that the driving circuit  58  applies to the motor  51 . 
     After the reverse voltages are generated by the motor  51  in step S 511 , the microprocessor  59  measures the reverse voltages generated in step S 511  and determines whether the measured reverse voltages are greater than a predetermined voltage value V 1  (S 512 ). If they are, the microprocessor  59  generates control signals for a normal motor brake, in which the braking resistor  55  is allowed to dissipate energy due to the reverse voltages generated by the motor  51  into heat (S 513 ). Otherwise, steps S 511  and S 512  are repeated until the reverse voltages are determined to be greater than V 1 . 
     Next, the microprocessor  59  measures a current-flow period of the braking resistor  55  which represents a length of time that a reverse current flows through the braking resistor  55  when the reverse voltages are generated by the motor  51 , and it further determines whether the measured current-flow period is less than a normal dissipate period T 1 (S 514 ). T 1  represents a period of time that it takes to dissipate all the reverse voltages by the braking resistor  55  in a normal condition. If the measured current-flow period is less than T 1 , the microprocessor  59  determines that the braking resistor  55  is opened. 
     If the measured current-flow period is determined to be not less than the T 1 , the microprocessor  59  determines whether the measured current-flow period is greater than T 1  (S 515 ). If the measured current-flow period is greater than T 1 , it determines that the braking resistor  55  is shorted. If it is determined that the measured current-flow period is less than or greater than T 1  in step S 514  or S 515 , the microprocessor  59  shorts a corresponding node connected to the driving circuit  58  for a predetermined period of time so as to reduce the reverse voltages generated by the motor  51  (S 516 ). When the node connected to the driving circuit  58  is shorted, the reverse voltages of the motor  51  are reduced due to their phase differences. By doing so, any circuit damage caused by high reverse voltages of the motor  51  can be prevented during the motor brake. 
     After the reverse voltages are reduced in step S 516  or the measured current-flow period of the braking resistor  55  is determined to be not greater than T 1  in step S 515 , the microprocessor  59  measures the reverse voltages of the motor  51  again and determines whether the measured reverse voltages are less than the predetermined voltage value V 1  (S 517 ). If they are, the microprocessor  59  terminates the operation of the motor  51  (S 518 ). 
     Embodiment (6) 
       FIG. 6A  illustrates a control system that drives a motor provided in a washer according to a sixth embodiment of the present invention. As shown in  FIG. 6A , the system includes a rectifier  611  rectifying the AC power, a motor  612  rotating a tub or an agitator of the washer, and a driving circuit  613  comprising a plurality of insulating gate bipolar transistors (IGBT). The driving circuit  613  applies input voltages U, V, and W having three different phases, respectively, to the motor  612  in a first operation mode and applies phase-reversed voltages to the motor  612  in a second operation mode so that the reverse voltages generated by the motor  612  due to its rotation are applied to the driving circuit  613 . 
     The system shown in  FIG. 6A  further includes a switching mode power supply (SMPS) unit  614  transforming the output of the rectifier  611  into a voltage having a predetermined level (e.g., 5V), a speedometer  615  measuring the rotational speed of the motor  612 , a braking resistor R b  dissipating the reverse voltages generated by the motor  612  into heat so as to prevent possible circuit damages, and a transistor T 1  driving the braking resistor R b . The system further includes a voltmeter  616  that measures the output voltage of the rectifier  611  after the reverse voltage of the motor  612  is dissipated in R b , a driver microprocessor  617  controlling operations of the driving circuit  613  and the transistor T 1  on the basis of the output voltage measured by the voltmeter  616 , a door opening sensor (not illustrated) detecting opening of a washer door and sending a corresponding signal to the drive microprocessor  617 , a user interface unit  618  having at least one a touch panel and a key input unit for receiving operational commands from a user, a display unit (e.g., LCD)  619  displaying a message indicating the operation status of the washer, a sound generating unit  620 , and a main microprocessor  621  controlling the drive microprocessor  617  so as to operate various components of the washer including the motor  612  according to the operational commands received by the user interface unit  618 . 
     The main microprocessor unit  621  detects an abnormal output voltage of the rectifier  611  by communicating with the drive microprocessor  617  and generates control signals to the display unit  619  and the sound generating unit  620  so as to display a warning message and a warning sound indicating the abnormal output voltage of the rectifier  611 . Because the brake resistor R b  is detachably provided in the control system as shown in  FIG. 6A  and the voltmeter  616  measures the output voltage of the rectifier  611  using R b , the output voltage of the voltmeter  616  will be 0V if R b  is not provided at all or the connector  622  is inoperatively provided. 
     Reference will now be made in detail to the operation of the control system shown in  FIG. 6A . When a user inputs commands for a wash cycle through the user through interface unit  618 , the main microprocessor  621  transmits control signals to the drive microprocessor  617  so as to drive various components of the washer based on a plurality of operation parameters corresponding to a wash option selected by the user. The drive microprocessor  617  initially rotates the motor  612  while monitoring the speed of the motor  612  and performs the wash cycle by operating other components such as a water supply system and a water drain system. On the other hand, the main microprocessor  621  generates control signals to the display unit  619  for displaying a current operation status of the washer and to the sound generating unit  620  for generating a warning sound if necessary. 
     During a wash cycle, the rotational direction of the motor  612  alternates between a clockwise direction and a counter-clockwise direction. For example, in order to switch the direction of the motor  612  which was initially rotating in a clockwise direction in a first mode, the rotation of the motor  612  must be initially stopped. In addition, such brake or interruption of the motor operation is often necessary when a washer door is opened by a user during a spin (dehydration) cycle. Therefore, when the drive microprocessor  617  determines that any one of the conditions for braking the motor operation is met, it operates the driving circuit  613  in a second operation mode, in which the driving circuit  613  applies phase-reversed input voltages to the motor  612  and the brake resistor R b  operates to dissipates the reverse voltage generated by the motor  611  so as to prevent any circuit damages. 
       FIG. 6B  is a flow chart illustrating a method of controlling a motor in a washer according to the sixth embodiment of the present invention. Initially, the drive microprocessor  617  measures the output voltage of the rectifier  611  using the voltmeter  616  (S 61 ). Next, if the drive microprocessor  617  determines that the measured output voltage is 0V (S 62 ), it transmits to the main microprocessor  621  a warning signal indicating that the brake resistor R b  is not connected at all or is improperly connected. Because the voltmeter  611  measures the output voltage of the rectifier  611  passing through R b  using a pair of resistors R 1  and R 2  connected in series, the measured voltage of 0V indicates that the power source voltage is being applied but R b  is improperly connected. 
     Upon receiving the warning signal from the drive microprocessor  617 , the main microprocessor  621  generate controls signals to the display unit  619  and the sound generating unit  620  for displaying a warning message indicating R b  is improperly connected and for generating a warning sound (S 63 ). If it is determined in step S 62  that the output voltage is not 0V, step S 63  is skipped. Next, if the main microprocessor  621  determines that operational commands for a wash cycle are inputted by a user through the user interface unit  618  (S 64 ), it further measures the output voltage of the rectifier  611  using the voltmeter  616  and determines whether the measured output voltage is 0V (S 65 ). If it is, the main microprocessor does not initiate the wash cycle but repeats step S 65  after being in a standby mode for a predetermined period of time. This step is essentially important for preventing any chance of damaging the control system shown in  FIG. 6A . 
     On the other hand, if it is determined in step S 65  that the measured output voltage is not 0V (meaning that R b  is now properly connected), the main microprocessor  621  initiates the wash cycle by generating control signals to the drive microprocessor  617  so as to operate various components of the washer including the motor  621  according to the operational commands received from the user (S 26 ). 
     Embodiment (7) 
       FIG. 7A  illustrates a control system controlling a motor in a washer according to a seventh embodiment of the present invention. Referring to  FIG. 7A , the control system includes a motor  71  rotating a tub or an agitator of the washer, a transformer  72  generating a DC power voltage, and a motor driving unit  73  driving the motor  71  by applying the DC power voltage to the motor  71 . The control system shown in  FIG. 7A  further includes a timer  74  counting a predetermined deceleration period, a voltmeter  75  measuring the reverse voltages generated due to reverse currents generated by the motor  71  when interrupted, and a microprocessor  76  that generates a control signal to the driving unit  71  to decrease the motor speed if the measured reverse voltages are less than a predetermined voltage value. 
     The microprocessor  76  initially accelerates the motor speed and controls the timer  74  to repeatedly count a predetermined deceleration period so as to reduce the initially accelerated motor speed for each deceleration period. In addition, the microprocessor  76  measures the DC input voltage of the motor driving unit  71  for each deceleration period and maintains a standby status to reduce the input voltage of the driving circuit  71  if the measured input voltage is higher than a predetermined voltage level. The voltmeter  75  is connected to the DC link in parallel and includes three resistors which are connected in series. Therefore, the output of the voltmeter  75  is a voltage subdivided by the resistors of the voltmeter  75 . 
     On the other hand, if the measured DC voltage of the driving unit  71  is less than the predetermined voltage level, the microprocessor  76  measures the current leading phase angle Φ and reduces the motor speed by reducing the leading phase angle by a predetermined rate for each deceleration period. If the leading phase angle Φ becomes zero, the microprocessor  76  obtains the current pulse width modulation (PWM) duty and reduces the motor speed by reducing the PWM duty by a predetermined rate for each deceleration period. 
     Reference will now be made in detail to a method of controlling a motor in a washer according to the seventh embodiment of the present invention, which is illustrated in  FIG. 7B . When the algorithm shown in  FIG. 7B  starts, the microprocessor  76  sends to a control signal to the timer  74  to start measure a time T and determines whether a predetermined deceleration period T c  is elapsed by checking whether T is greater than T c  (S 701 ). If T c  is elapsed, the microprocessor  76  initializes the timer  74  by setting T to zero (S 702 ) and determines whether the current DC voltage V of the driving unit  71  is less than or equal to a predetermined voltage level V c  (S 703 ). If it is determined in step S 703  that V V c , then the microprocessor  76  measures the current leading phase angle Φ of the DC voltage V of the driving unit  71  (S 704 ). If the measured leading phase angle Φ is greater than zero (S 705 ), the microprocessor  76  reduces the leading phase angle Φ by a predetermined level α (S 706 ). Thereafter, if the microprocessor  76  determines that the motor  71  is not stopped (S 711 ), step S 701  and all the following steps are repeated again as shown in  FIG. 7B . 
     On the other hand, if it is determined in step S 705  that the measured leading phase angle Φ is not greater than zero, the microprocessor  76  further determines whether the measured leading phase angle Φ is equal to zero (S 707 ). If it is equal to zero, the microprocessor  76  obtains the current PWM duty (S 708 ). If the current PWM duty is greater than zero (S 709 ), it reduces the PWM duty by a predetermined level β. Next, if it determines that the motor is not stopped (S 711 ), all the previous steps are repeated again. In addition, if it is determined in step S 704  that the measured DC voltage V is greater than V c , steps S 704  to S 719  are skipped and step S 711  is performed. 
     Embodiment (8) 
       FIG. 8A  illustrates an apparatus of controlling operation of a motor in a washer according to an eighth embodiment of the present invention. Referring to  FIG. 8A , the apparatus includes a key input unit  810  receiving commands from a user for a wash cycle, a motor  830  rotating a tub and/or an agitator of the washer, and a controller  820  generating control signals to perform the wash cycle according to a wash option selected by the user and to lock a wash door (not illustrated) if the speed of the motor  830  is equal to a predetermined speed. The apparatus shown in  FIG. 8A  further includes a washer door locking unit  850  that locks or unlocks the washer door of the washer, a speed measuring unit (e.g., a speedometer)  840  measuring the rotating speed of the motor  830  and providing the measured speed to the controller  820 , and a display unit  860  that displays a message indicating the locking status of the washer door upon receiving a control signal from the controller  820 . 
     When a user inputs commands for a wash cycle through the key input unit  810 , the controller  820  generate control signals to perform a wash cycle, a rinse cycle, and a spin (dehydration cycle). After the spin cycle is initiated, the controller  820  generates a control signal to the wash door locking unit  850  to lock the washer door when the speed of the motor  830  reaches a first predetermined motor speed. When the speed of the motor further reaches a second predetermined motor speed, the controller  820  maintains the speed of the motor  830  until the spin cycle is finished. 
     Reference will now be made in detail to a method of controlling operation of a motor in a washer according to the eighth embodiment of the present invention. Referring to  FIG. 8B , if the controller  820  determines that a spin cycle (dehydration cycle) is ordered (S 801 ), it increases the speed W of the motor  830  (S 802 ). Next, if the controller  820  determines that W is equal to a first predetermined motor speed W 1 , e.g., 700 RPM (S 803 ), it sends a control signal to the washer door locking unit  850  to lock the washer door of the washer (S 804 ). If W is determined to be less than W 1  in step S 803 , the controller  820  repeats step S 802  until W becomes W 1 . After the washer door is locked in step S 804 , the controller  820  further increases the motor speed W (S 805 ). If it is determined that W has reached a second predetermined motor speed W 2 , e.g., 1000 RPM, which is greater than W 1  (S 806 ), the controller  820  maintains the motor speed W until the spin cycle is finished (S 807  and S 808 ). As described above, the controller  820  does not lock the washer door until the speed of the motor  830  reaches to the first predetermined motor speed W 1  so that the power consumption and durability of the door lock are greatly improved. 
     Embodiment (9) 
       FIG. 9A  illustrates a control system that drives a motor provided in a washer according to a ninth embodiment of the present invention. The motor control system shown in  FIG. 9A  illustrates a rectifier  911  rectifying the AC power, a motor  912  rotating a tub or an agitator of the washer, and a driving circuit  913  comprising a plurality of insulating gate bipolar transistors (IGBT). The driving circuit  913  applies input voltages U, V, and W having three different phases, respectively, to the motor  912  in a first mode and applies phase-reversed voltages to the motor  912  in a second mode so that the reverse voltages generated by the motor  912  due to its rotation are applied to the driving circuit  913 . 
     The control system shown in  FIG. 9A  further includes a switching mode power supply (SMPS) unit  914  transforming the output of the rectifier  911  into a voltage having a predetermined level (e.g., 5V), a speedometer  915  measuring the rotational speed of the motor  912 , a braking resistor R b  dissipating the reverse voltages generated by the motor  912  into heat so as to prevent possible circuit damages, and a transistor T 1  driving the braking resistor R b . The control system further includes a voltmeter  916  measuring the output voltage of the rectifier  911  after the reverse voltages of the motor  912  are dissipated in R b , a microprocessor  917  controlling operations of the driving circuit  913  and the transistor T 1  on the basis of the output voltage measured by the voltmeter  916 , and a door opening sensor (not illustrated) detecting opening of a washer door and sending a corresponding to the microprocessor  917 . 
     Reference will now be made in detail to a method of controlling a motor in a washer according to the ninth embodiment of the present invention, which is illustrated in  FIG. 9B . Referring to  FIG. 9B , when a user inputs commands for washing a load of clothes to be washed, the microprocessor  917  operates the driving circuit  913  so as to rotate the motor  912  based on a wash algorithm or program that correspond to the user input commands so that a tub and an agitator of the washer are rotated for performing wash and rinse cycles. Thereafter, the microprocessor  917  initiates a spin (dehydration) cycle by increasing the speed of the motor  912  (S 931 ). The speed of the motor  912  in a spin cycle should be determined based on a total weight of the load of clothes to be dehydrated or weight distribution of the load, but is typically greater than 100 rpm. 
     After a spin cycle is initiated in step S 931 , the microprocessor  917  determines whether a motor brake is necessary by determining any one of the conditions for braking motor operation is met (S 932 ). For example, if a motor interruption command inputted by a user or a signal indicating opening of a washer door is received, or if the speed of the motor  912  measured by the speedometer  915  is determined to be abnormal, the microprocessor  917  determines that interruption (brake) of the motor operation is necessary. If any one of such conditions is met, the microprocessor  917  determines whether the current speed W of the motor  912  is greater than a first critical speed W 1  (S 933 ). W 1  (typically set to 1000 rpm) represents the minimum speed of the motor  912  that can mechanically damage the motor  912  or any other components that associate with the motor  912  (e.g., a clutch) when a rapid brake of the motor operation is performed. If it is determined in step S 933  that W is greater than W 1 , the microprocessor  917  controls the driving circuit  913  to short power input terminals of the motor  912  for a predetermined period of time in order to brake the motor operation (S 934 ). By doing so, rather a slow motor brake is achieved so that any mechanical damage due to a rapid motor brake can be prevented. 
     Next, the microprocessor  917  further determines whether the current speed W of the motor  912  is less than W 1  and is greater than a second critical speed W 2  (S 935 ). W 2  (typically set to 100 rpm) represents the allowable speed of the motor  912  that does not create any mechanical damage even if a rapid brake of the motor operation is performed. If it is determined in step S 935  that W is less than W 1  and is greater than W 2 , then microprocessor  917  performs a rapid motor brake by operating the driving circuit  913  to apply phase-reversed voltages to the motor  912  for a predetermined period of time and by operating the brake resistor R b  so as to dissipate the reverse voltages generated by the motor  912  during the rapid motor brake (S 936 ). In the method shown in  FIG. 9B , a same rapid brake is performed when W is in a signal speed range of W 1  to W 2 . However, different rapid brakes can be performed for a plurality of subdivided ranges of the motor speed by using different duty rations when applying the phase-reversed voltages to the motor  912 . 
     Furthermore, the microprocessor  917  further determines whether the current speed W of the motor  912  is less than W 2  (S 937 ). If it is, the microprocessor  917  controls the driving circuit  913  to short the power input terminals of the motor  912  in order to brake the motor operation (S 938 ). Since W is less than 100 rpm, the motor operation can be easily. Thereafter, if the microprocessor  917  determines that the motor operation is terminated (S 939 ), then it ends the motor control algorithm. Otherwise, steps S 933  to S 939  are repeated. 
     Referring back to step S 932 , if none of the conditions for braking motor operation are met and if the spin cycle is determined to be terminated in step S 940 , the microprocessor  917  ends the motor control algorithm. 
     Embodiment (10) 
       FIG. 10  illustrates a circuitry for limiting a motor current in an electrical appliance according to a tenth embodiment of the present invention. Referring to  FIG. 10 , the current limiting circuitry includes a microprocessor  999 , a power source V cc  supplying a source voltage of 5V, a first resistor R 1  having a resistance of 33 k and a dip switch  997  connected between the power source V cc  and a ground in series, a capacitor C 1  connected to the dip switch  997  in parallel, an op amp  998  having an inverting input connected to a node between R 1  and the dip switch  997  and an output connected to the microprocessor  999 , and a third resistor R 3  having a resistance of 0.027 k, which is connected between the noninverting input of the op amp  998  and a ground. 
     Reference will now be made in detail to the operation of the current limiting circuitry shown in  FIG. 10 . The dip switch  997  comprises a plurality of resistors having different resistances (e.g., 1.3 k, 1.5 k, 1.8 k, 2.0 k, and so on). Therefore, an appropriate one of the plurality of resistors can be conveniently selected for selecting a limited current value. For example, if a resistor having a resistance of 1.3 k is selected by the dip switch  997 , then the limited current that flows through R 3  is
 
 I ={(5*1.3)/(33+1.3)}/0.027=7A.
 
Alternatively, if a resistor having a resistance of 1.8 k is selected by the dip switch  997 , the limited current that flows through R 3  is
 
 I ={(5*1.8)/(33+1.8)}/0.027=9A.
 
     As shown in the examples shown above, the value of the limited current that flows through R 3  is varied based on the switching of the dip switch  997 . When more than one resistors are selected by the dip switch  997 , the value of the current that flows through R 3  can be even lower since the selected resistors are in parallel. Instead of using the dip switch  997 , a resistance-variable resistor can be used. However, it has a disadvantage that it is difficult to set a precise resistance value of the resistance-variable resistor. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.