Abstract:
An improved energy controller that increases the electrical efficiency of AC induction motors and electrical lights that is comprised of a microcontroller integrated with a signal control circuit to regulate the amount of the input line A/C signal that passes from the input the to electrical device. The microcontroller includes circuitry to measure the phase of the voltage and current of the input A/C signal and the shift of the phase across the motor or electric light. Using this phase difference, the microcontroller can determine the power factor and regulate the amount of power provided to the electric motor or light in response to changes in loading on the motor or light. The energy controller includes software that enables the microcontroller to provide a soft-start for induction motors.

Description:
FIELD OF THE INVENTION 
     This invention generally relates to the field of electrical systems that are employed to reduce the energy consumption of electrically-powered devices. More specifically, the present invention relates to an energy management device that employs a micro-controller and software system to regulate an A/C signal to reduce the energy consumption of an induction motor. 
     BACKGROUND 
     Reducing energy consumption is a prime goal in the world today. For consumers, reducing the amount of energy they consume individually lowers their personal energy costs. In addition, reduced energy consumption helps to conserve our natural resources and protect the environment. 
     At present, there are many energy saving systems in existence that reduce the energy consumption of electrical devices. One electrical device that can have its power consumption reduced by an energy saving device is an induction motor. Induction motors are commonly used for a wide variety of residential, commercial, and industrial purposes. The power requirements of an induction motor typically vary during operation. The inherent design of an induction motor causes it to use excessive current and voltage even under light or no load conditions. One measure of induction motor efficiency is to value the voltage applied as a function of motor load. Induction motors draw the same current whether loaded or unloaded. As a result, the motor efficiency decreases as the load decreases. In other words, an AC induction motor will consume much more energy than it requires under light load conditions. 
     AC induction motors are rather inefficient when they are not matched properly to their load. A motor is most efficient when it is heavily loaded and the rotor slips from its unloaded synchronous speed. As a bi-product of rotor slip, power factor is effected making the current closer in phase of the voltage. 
     Rotor slip can be induced not only by loading a motor, but also by reducing its average power supplied in such a manner as to remove sections of, the sinusoidal excitation waveform. Such a technique can greatly enhance the efficiency of the motor under light load conditions. The ultimate result is realized in power savings and lower operating costs. 
     Currently, many devices exist that vary the power supplied to the induction motor to enhance motor efficiency. U.S. Pat. No. 4,404,511 issued to Nola teaches a motor controller that is designed to enhance induction motor efficiency. A resistor is used to sense the input current to the motor. A circuit is used to generate a control signal that represents the phase shift difference between the motor current and motor voltage, which is the power factor. As the loading on the motor changes, the power factor changes. When the power factor is changed due to a decrease in the load on the motor, the device increases the off time of the duty cycle of the AC line power applied to the induction motor thereby reducing the current used by the motor. In this arrangement, the amount of power savings is scaled according to the power used by the device. 
     The key aspect of the device disclosed in Nola is that it senses the current using a resistive element. The Patent issued to Nola represents a class of energy management devices for induction motors that use resistive elements to measure current. The use of resistors to measure current has many disadvantages. First, the resistors required for measuring current are typically very large physically. This large physical size prevents the ability to fully miniaturize these devices. In addition, the cost of reliable resistive devices is typically very high. Further, resistors produce a great deal of heat while measuring the current. This heat reduces the efficiency of the device. Also, this heat can pose a design problem for the device since it also uses a microcontroller that must operate within a certain temperature range. It is therefore highly desirable to develop a system that can determine the phase shift without using a resistive element to measure current. 
     It is possible to determine a phase shift between the current and voltage without using a resistive element to measure the current. It is possible to determine the power factor by measuring the point where the current and voltage of and AC signal crosses zero. A voltage sampler circuit provides signals that indicate when the voltage applied to the motor crosses zero. An additional circuit is used to provide a signal that indicates when the current flow through the motor crosses zero. This system of measuring the power factor does not use any resistive elements. This method of sampling the zero point of the current and the voltage, referred to as the zero point system, has many advantages over the method that uses resistive elements. First, due to the fact that it uses no resistive elements, the zero point system is less expensive to manufacture. In addition, the zero point system uses less energy due to the lack of any resistors. Also, not using any resistors lowers the heat produced by the device. Finally, it is possible to miniaturize the circuitry of the zero point system to a greater extent since it does not include resistors. 
     U.S. Pat. No. 5,592,062 issued to Bach, the inventor of the technology disclosed in this application, teaches an energy controlling circuit for use with AC induction motors. The patent issued to Bach teaches the use of circuitry that determines when the current and voltage cross zero to find the power factor. This device utilizes a microcontroller in conjunction with a triac to control the duty cycle of the AC power applied to the motor. A voltage sensing circuit provides signals to the microcontroller. The micro controller is also coupled to the gate of the triac. The microcontroller automatically selects the appropriate parameters for most efficient motor operation based upon the motor power factor by the time at which the voltage across the motor crosses zero and the voltage at the triac gate crosses zero. 
     In addition to induction motors, various other electrical devices such as electric light bulbs do not operate at peak efficiency. It is also possible to enhance the electrical efficiency of these electrical devices by measuring the load across the light bulb and altering the input signal accordingly. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved energy controller that increases the electrical efficiency of AC induction motors, electric lights, and other electrical devices. The invention is an integration of electrical circuitry and computer software to regulate the power supplied to the induction motor or electric light thereby enhancing the efficiency of the motor or light. As stated earlier, the inherent design of the induction motor causes it to use excessive current and voltage even under light or no-load conditions. The present invention takes advantage of this design by reducing the current and voltage consumed by the motor when not fully loaded. The frequency and peak voltage are not changed so the motor speed is not affected. The invention monitors the AC signal and senses when the motor is consuming more power than required. When the motor consumes more power than required, the invention removes a portion of the AC signal thereby allowing the motor to continue its rotational motion while consuming less energy. The amount of the signal that is removed, or “clipped,” is determined by the actual load on the motor. The actual load on the motor is calculated by the invention by comparing current and voltage phase angles. Under light loads, the amount of voltage removed from the AC signal is large. As the load demanded by the motor increases, the width of the slice removed from the signal will decrease, to the point where under fully loaded conditions the slice removed is negligible and full power is allowed to flow to the motor. 
     For electric lights, the microcontroller measures the loading across the light bulb and accordingly reduces the input A/C signal to the minimum level power level where the quality of light emitted from the light bulb is not reduced. 
     The present invention is comprised of a software-controlled microcontroller. The microcontroller is connected to circuitry that measures when the voltage and current cross the zero reference point along the current or voltage axis. In addition, the invention includes a bypass or relay circuit that can bypass the microcontroller and signal clipping circuitry and supply the input AC signal directly to the induction motor or electric light. 
     In addition, the present invention includes software that determines whether the device is functioning correctly. In the event the invention is not properly measuring the phase shift, or correctly clipping the AC signal; the software activates a bypass circuit and turns the remainder of the device off. The bypass circuit allows the AC input signal to flow unaffected to the induction motor or electric light. The use of this bypass circuit is also an improvement over patent, U.S. Pat. No. 5,592,062. 
     A further improvement over U.S. Pat. No. 5,592,062, is the use of a silicon control rectifier in place of the triac disclosed in the previous patent. The triac in the previous patent is used to control the amount of voltage supplied to the motor. The silicon control rectifier performs the same function. However, the silicon control rectifier has many advantages over the triac making the present invention superior to the invention disclosed in U.S. Pat. No. 5,592,062. The silicon control rectifier is cheaper to manufacture and is physically smaller in size. 
     In addition, the present invention is designed to provide a “soft start” for induction motors. Induction motors draw a large amount of power when they are turned on thereby placing a lot of strain on the power system supporting the motor. One way to eliminate the strain on the power system caused by turning on the induction motor is to soft start the motor. A soft start occurs when the voltage applied to the motor is gradually raised. 
     The primary object of the invention is to provide a new and improved energy control device for induction motors and electric lights. 
     It is another object of the invention is to provide circuitry and software that will shut the device down if it is not functioning correctly. 
     Another object of the invention is to use software to measure the power factor thereby eliminating the need for a resistive element to measure the current going through the motor or electric light. 
     A still further object of the invention is to pass the input AC signal directly to the induction motor or electric light in the event that the device is shut down. 
     Another object of the invention is to reduce the cost and size of energy control devices by replacing the triac circuit with a silicon control rectifier. 
     A further object of the invention is to provide an option to have a soft start for induction motors. 
     Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize this invention are pointed out with particularity in the claims annexed to and forming a part of this specification. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself; however, both as to its structure and operation together with the additional objects and advantages thereof are best understood through the following description of the preferred embodiment of the present invention when read in conjunction with the accompanying drawings wherein: 
     FIG. 1 shows a circuit diagram of the device; 
     FIG. 2 shows a modified A/C signal; 
     FIG. 3 shows the process of how the device provides a soft start; and 
     FIG. 4 shows the energy saving process. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A circuit diagram showing the power savings device  100  is shown in FIG.  1 . The power savings device  100  is used to regulate the power supplied to a motor  110  or electric light  110 . The remainder of this application will describe the use of the power savings device  100  with the induction motor  110  as an example. However, the structure and function of the device  100  is the same if another electrical device such as an electric light were attached to the device  100  instead of the induction motor  110 . The power savings device  100  is controlled by an 8-bit RISC microcontroller  120  that is operated by a software program contained in a Read Only Memory (ROM). The microcontroller  120  includes a microprocessor, memory, and an analog/digital converter. The microcontroller  120  is a commercially available product. The processes executed by the software program are shown in FIGS. 3 and 4. The power savings device  100  includes a rectifier  150 . The rectifier circuit  150  measures the phase of the voltage of the line A/C signal when the line A/C signal is at zero volts. The line A/C signal that powers motor  110  is placed across the inputs  115 . The portion of the line A/C signal that passes through to the controller is modified by the pair of diodes  160 . The pair of diodes  160  modifies the A/C signal into a square wave, which is the input signal for the microcontroller  120 . An opticoupler  165  connected to the microcontroller  120  is used to sense the point where the voltage applied across the motor crosses the zero mark. The microcontroller  120  uses the phase of the input A/C signal determined by the rectifier  130  and the zero crossing point of the A/C signal across the motor  110  found by the opticoupler  165  to calculate the power factor of the motor  110 . 
     The microcontroller  120  uses another opticoupler  166  to regulate a signal control circuit  200 . The signal control circuit  200  is used to control the amount of the line A/C signal that is passed through to the motor  110  is regulated by the signal control circuit  200 . The microcontroller  120  uses the signal control circuit  200  to clip the input A/C line signal to reduce the power supplied to the motor  110 . The signal control circuit  200  is constructed using a pair of silicon control rectifiers  210 . 
     The power savings device  100  includes a relay circuit  130 . The relay circuit  130  is a failsafe feature. In the event that the power savings device  100  is not functioning properly, the relay circuit  130  is activated by the microcontroller  120 . The relay circuit  130  bypasses the signal control circuitry  200  and passes the input A/C signal directly to the motor  110 . 
     The mircocontroller  120 , relay circuit  130 , rectifier  150 , and signal control circuit  200  are coupled to form a signal circuit having an input  115  and an output  117 . An input voltage signal appears at the input  115 . An electrical device  110  such as an electric light or induction motor  110  is connected to the output  117 . An output signal is measured across the output  117 . 
     The microcontroller  120  is programmed to turn on the motor  110  in two ways. One method of turning on the motor  110  is through a soft-start. Under a soft-start, the voltage applied to motor  110  is gradually raised from a zero level. This gradual rise in the voltage increases the motor 110 rpm from zero to a nominal value. Alternatively, the motor can be turned on in a cold-start. In a cold start, the full A/C input line voltage is applied to the motor  110 . A jumper  116  is used to program the microcontroller to operate in the soft-start mode or the cold-start mode. 
     FIG. 2 shows an input A/C signal and how the power saving device  100  alters the signal under normal operation. The pure sinusoidal signal  250  is the line input A/C signal that appears at the inputs  115 . The darkened portion  251  of the signal  250  is that portion of the sinusoid that is clipped by the signal control circuit  200 . Through clipping the signal  250  at the point after the signal crosses the zero mark, the peak voltage and frequency of the signal is not changed. 
     The process of activating the energy power saving device  100  is shown in FIG.  3 . The user of the device  100  can select whether to turn on the motor with a soft-start in step  301  through the placement of jumper  116 . Under a soft-start, the voltage applied to motor  110  is gradually raised from a zero level. This gradual rise in the voltage increases the motor  110 -rpm from zero to a nominal value. Opticoupler  165  is used to sense the A/C voltage across the motor  110  and note when that A/C signal voltage crosses the zero level. The silicon control rectifiers  210  control the amount of voltage that is passed through to the motor  110 . Under soft-start, the silicon control rectifiers  210  are fired in calculated periods of time to allow portions of the input A/C signal to pass through to the motor  110 . A soft-start is selected by the positioning of a jumper cable  116  provided on the device. If a soft-start has been selected, the system  100  proceeds to steps  302  and  303 . The microcontroller  120  fires the silicon control rectifiers  210  in step  302  in time periods to slowly increase the voltage level from a zero level to a higher level. In step  303 , the microcontroller  120  determines if the voltage has been raised to a level where the motor  110  is operating at a nominal rpm. If the motor  110  is not operating at a nominal rpm, the microcontroller  120  continues to increase the amount of the input A/C signal that is passed through to the motor  110  through controlling the silicon control rectifiers  210  under step  302 . When the motor  110  is operating at a nominal rpm, the microcontroller  120  activates the energy saving system  400  in step  305 . 
     In the event that a soft-start is not selected in step  301 , the motor  110  is activated under a cold-start. Under a cold-start, the full A/C signal is passed through to the motor  110  and the energy saving system  400  is activated in step  305 . 
     The energy saving system  400  is shown in FIG.  4 . The first step in the energy saving system is to determine the power factor in step  401 . In order to determine the power factor, it is necessary to measure the zero voltage crossing of the line voltage A/C waveform and the zero voltage crossing of the voltage waveform across opticoupler  165 . Since the opticoupler  165  is in phase with the motor  110 , the zero voltage crossing of the opticoupler  165  has the same phase as the zero voltage crossing as the waveform across the motor  110 . The microcontroller  120  senses the zero voltage crossing of the line voltage A/C wave form from the output of the signal generated by the rectifier  150  and diodes  160 . The microcontroller  120  also senses the zero voltage crossing of the voltage at the opticoupler  165 . Using this data, the microcontroller  120  determines the power factor. 
     Through determining the power factor, the microcontroller  120  is programmed to determine if there is a change in the power factor in step  402 . A change in the power factor indicates that there is a change in the loading on the motor  110 . If there is no change in the power factor, the microcontroller  120  provides a control signal at its output to regulate the firing of the silicon control rectifiers  210  to maintain the amount of the A/C input signal that is passed through to the motor  110 . The microcontroller  120  then proceeds back to step  401  to determine the power factor and then recalculates if a change has occurred. Once a change in the power factor is detected, the microcontroller  120  proceeds to step  403 . In step  403 , the microcontroller  120  provides a control signal at its output to regulate the firing of the silicon control rectifiers  210  at a different time period to account for the change in loading. In the event that power factor changes due to a decrease in the loading, the microcontroller  120  will regulate the silicon control rectifiers  210  to reduce the amount of the A/C signal that is passed through to the motor  110 . If instead, the power factor changes due to an increase in the loading on the motor  110 , the microcontroller  120  will regulate the silicon control rectifiers  165  to increase the amount of the A/C signal that is passed through to the motor  110 . 
     During the operation of the power savings system  400 , the microcontroller  120  performs a check  404  to determine if the power savings system  400  is functioning within nominal operating parameters. If the power savings system  400  is functioning within nominal operating parameters, the microcontroller  120  continues to execute steps  401 ,  402 ,  403 , and  404  as shown in FIG.  4 . However, in the event that the microcontroller  120  detects that the power savings system  400  is not functioning correctly, the microcontroller  120  will activate the relay switch  130 . The relay switch  130  is designed to bypass the signal altering circuitry including the microcontroller  120  and signal control circuit  200  and pass the input A/C signal unaffected to the motor  110 . In addition, when a malfunction is detected in the power savings system  400 , the microcontroller  120  turns the power savings system  400  off and the program ends until restarted. 
     While the invention has been shown and described with reference to a particular embodiment thereof, it will be understood to those skilled in the art, that various changes in form and details may be made therein without departing from the spirit and scope of the invention.