MOTOR CONTROLLER

Abstract: A motor controller made up of a power supply circuit rectifying an AC power supply for outputting desired DC voltages and, at the same time, improving the power factor of the AC power supply and a motor drive circuit for driving a motor. The same comprises a rectifier circuit for converting AC power supply to DC and a smoothing circuit, a converter circuit constituted of a chopper circuit for controlling the DC voltage by utilizing switching operation and inductance's energy storing effect, a motor drive device made up of an inverter circuit connected to the output of the converter circuit and a motor, a converter control circuit for controlling the switching operation of the chopper circuit, an inverter control circuit for controlling the switching operation of the inverter circuit thereby driving the motor, a speed detector circuit for detecting the position of the rotor of the motor and calculating the speed of the motor, a speed control circuit receiving the calculated speed value and a speed command value for controlling the motor speed through the inverter circuit, and a DC voltage control circuit receiving the output signal of the speed control circuit for controlling the DC voltage through the converter control circuit in accordance with the output signal. The DC voltage control circuit, when the output of the speed control circuit reaches a predetermined value, outputs a signal to cause the DC voltage to increase or decrease to the converter control circuit. The output of the speed control circuit is a duty ratio signal or a speed deviation signal of the calculated speed value from the speed command value.

Description: Technical Field The present invention relates to a motor controller made up of a power supply circuit rectifying an AC power source for outputting desired DC voltages and, at the same time, improving the power factor of the AC power source and a motor drive circuit for driving a motor. Background Art As a motor controller being a rectifying circuit rectifying an AC power source for converting it into a DC power supply and performing speed control of a motor by using, in combination, a power supply circuit suppressing harmonics occurring in the power source current and a motor driving circuit, the one disclosed in Japanese Laid-open Patent No. Hei 6-105563 is known. The motor controller is formed of a power factor improving converter circuit employing a step-up chopper circuit, which simultaneously performs suppression of harmonics in the power source current and control of the DC voltage, and an inverter circuit for driving the motor. The motor controller, at the time of low load, controls the DC voltage to take on the lowest voltage value allowing the power factor to be improved and performs speed control of the motor through PWM control by the inverter circuit and, at the time of high load, stops the PWM control performed by the inverter but performs speed control of the motor through DC voltage control by the converter, i.e., PAM control. In the above described prior art technology, the configuration of the motor speed control circuit at the time of low load and that at the time of high load was different and different speed controlling operations were necessary according to the conditions of the load. Namely, at the time of low load, the duty ratio of the PWM signal for the inverter was calculated from the speed deviation and, at the time of high load, the DC voltage command for the converter was calculated from the speed deviation. Further, switching between the control circuit at the time of low load and the control circuit at the time of high load was carried out in accordance with the DC voltage value of the duty ratio of the PWM signal for the inverter, the speed command value, and the present speed. However, in the above described prior art, it is required to have two kinds of speed control circuits for low load operation and high load operation and hence, the control circuit becomes complex. Further, since the determination of switching of the control circuits for the low load operation and high load operation is made by using a number of different signals, many detector circuits are required. US 4 855 652 discloses a speed control apparatus for a brushless direct current motor. It comprises a rectifier, a chopper and an inverter. It further comprises a first speed control apparatus controlling the chopper circuit and a second speed control apparatus controlling the inverter. Document US 4 810 948 discloses a control circuit for controlling a DC voltage comprising a plurality of detection terminals, one of them being selected in accordance with an external signal for controlling the DC voltage. It is the object of the invention to provide a motor controller capable of rendering a motor control which is less affected by pulsating components in the DC voltage. This object is solved by a motor controller having the features of claim 1. Disclosure of Invention The invention is a motor controller comprising a rectifier circuit for converting AC power to DC and a smoothing circuit, a converter circuit constituted of a chopper circuit for controlling DC voltage by utilizing switching operation and inductance's energy storing effect, a motor drive device made up of an inverter circuit connected to the output of the converter circuit and a motor, a converter control circuit for controlling the switching operation of the chopper circuit, an inverter control circuit for controlling the switching operation of the inverter circuit for driving the motor, a speed detector circuit detecting the position of the rotor of the motor for calculating the speed of the motor, a speed control circuit receiving the calculated speed value and a speed command value for performing speed control of the motor through the inverter control circuit, and a DC voltage control circuit receiving the output signal of the speed control circuit for controlling the DC voltage through the converter control circuit in accordance with the output signal. As a preferred embodiment, the DC voltage control circuit is adapted to output to the converter control circuit a signal causing the DC voltage to increase or decrease when the output of the speed control circuit reaches a predetermined value. As a preferred embodiment, the DC voltage control circuit is adapted to control the DC voltage through the converter control circuit such that the output of the speed control circuit takes on a predetermined value. As a preferred embodiment, a duty ratio signal or a speed deviation signal of the calculated speed value from the speed command value is provided as the output of the speed control circuit. In the above described structure, the inverter control circuit drives the switching device of the inverter to drive the motor in accordance with the position signal from the speed detector circuit and the duty ratio signal from the speed control circuit. The speed detector circuit detects an induced voltage by the motor and calculates the position of the rotor from the induced voltage to output the detected position signal in a pulse form and, at the same time, calculates the speed from the calculated position signal to output the same as the detected speed value to the speed control circuit. The speed control circuit calculates the duty ratio signal of the PWM pulse for the inverter from an external speed command and the detected speed value so that the speed deviation becomes zero. The inverter circuit, motor, speed detector circuit, inverter control circuit, and the speed control circuit constitute a motor speed control circuit, and speed control of the motor is executed in accordance with the external speed command. The converter control circuit controls the switching device of the chopper circuit in accordance with the signal from the DC voltage control circuit. The DC voltage control circuit detects the DC voltage and the output signal of the speed control circuit, for example the duty ratio signal, and controls the DC voltage such that the DC voltage rises by a predetermined amount when the duty ratio signal reaches a predetermined value, for example the upper limit value of a range of the duty ratio signal, and such that the DC voltage falls by a predetermined value when the duty ratio signal reaches the lower limit value. The converter circuit, converter control circuit, and the DC voltage control circuit constitute a DC voltage control circuit of the converter and the DC voltage is controlled thereby. By combining the motor speed control circuit with the converter DC voltage control circuit and allowing both the circuits to operate respectively, speed control of the motor can be achieved by the use of a simple structure irrespectively of the load conditions. Brief Description of Drawings FIG. 1 is a block diagram of a motor controller according to a first embodiment of the invention and FIG. 2 is a drawing showing a configuration of a DC voltage control circuit as a constituent of the motor controller. FIG. 3 and FIG. 4 are explanatory drawings of operations of the motor controller according to the first embodiment of the invention. FIG. 5, FIG. 6, FIG. 7, and FIG. 8 are drawings showing other configurations of the DC voltage control circuit as a constituent of the motor controller according to the first embodiment of the invention. FIG. 9 and FIG. 10 are explanatory drawings of the operations of the motor controller according to the first embodiment of the invention in the cases where the DC voltage control circuits shown in FIG. 7 and FIG. 8 are used. FIG. 11 is a drawing showing another configuration of the DC voltage control circuit as a constituent of the motor controller according to the first embodiment of the invention. FIG. 12 is a block diagram of a motor controller according to another embodiment of the invention and FIG. 13 is a drawing showing a configuration of a DC voltage control circuit as a constituent of the motor controller. FIG. 14 is a block diagram of a motor controller according to still another embodiment of the invention and FIG. 15 is an explanatory drawing of correcting operation of pulsation of DC voltage performed in the motor controller. FIG. 16 is a block diagram of an air conditioner to which the motor controller of the invention is applied. FIG. 17 is a drawing showing a configuration of a converter module with a portion of the constituents of the motor controller of the invention modularized. Best Mode for Carrying Out the Invention Detailed description of the invention will be given with reference to the accompanying drawings. FIG. 1 and FIG. 2 are drawings for explaining a first embodiment of the motor controller of the invention. FIG. 1 is a general structural drawing of the motor controller comprising a converter circuit, which employs a rectifier circuit and a step-up chopper circuit, and a motor driving circuit formed of an inverter circuit and a motor. An AC power source 1 is connected to a converter circuit 2 and output as a DC voltage through the converter circuit 2 constituted of a rectifier circuit and a step-up chopper circuit which is formed of a reactor, a diode, and a transistor. The step-up chopper circuit in the converter circuit 2 is connected to the output side of the rectifier circuit in the converter circuit 2 and forces the input current to flow by switching action of the transistor and energy storing effect of the reactor to thereby step up the voltage. The stepped up DC voltage is supplied to a smoothing capacitor and a stabilized DC voltage is output therefrom. An inverter 3 connected with a synchronous motor 4 is connected to the smoothing capacitor within the converter circuit 2 and converts the DC voltage supplied from the smoothing capacitor into desired AC voltages to drive the synchronous motor 4. A speed detector circuit 5 calculates the position of the magnetic pole from the induced voltage by the synchronous motor 4 and outputs a position signal to an inverter control circuit 6. It further performs speed calculation on the basis of the calculated position signal and outputs the detected speed value to a speed control circuit 7. The speed control circuit 7, on the basis of the detected speed value from the speed detector circuit 5 and an external speed command, outputs a duty ratio signal to the inverter control circuit 6 so that the speed deviation becomes zero. The inverter control circuit 6, on the basis of the detected position signal from the speed detector circuit 5 and the duty ratio signal from the speed control circuit 7, generates a drive signal to drive the transistor in the inverter 3 to thereby perform speed control of the synchronous motor 4. A converter control circuit 8 drives the transistor within the converter circuit 2 in accordance with a current command value from a DC voltage control circuit 9 and controls the input current to the converter circuit 2 to have a sine wave to thereby improve the power factor of the power source and control the DC voltage at the same time. The DC voltage control circuit 9 detects the duty ratio signal as the output of the speed control circuit 7 and controls the DC voltage in accordance with the value of the duty ratio signal. FIG. 2 shows an internal structure of the DC voltage control circuit 9. The DC voltage control circuit 9 is formed of a selector circuit 93 and a multiplexer 95 selecting, in accordance with the duty ratio signal, one of a plurality of DC voltage command values generated by a DC voltage command value generator circuit 96 and outputting the selected signal, a detector circuit 94 detecting the output DC voltage from the converter circuit 2 and converting the same into a voltage value at the level usable in the control circuit 2, a proportional term 91, and an integral term 92. The proportional term 91 and the integral term 92 operate so that the deviation of the dc voltage detection value from the DC voltage command value may become zero and outputs the result as a current command. The multiplexer 95 is a circuit selecting one of the plurality of provided DC voltage command values in accordance with the external signal and outputting only the selected DC voltage command value. In the example shown in FIG. 2, there are arranged the DC voltage command values from 1 to 4 in ascending order of the value. The DC voltage command value 1 is set to the lowest DC voltage that is controllable by the converter circuit 2. The selector circuit 93, upon receipt of the duty ratio signal as the output of the speed control circuit 7, outputs a switch signal corresponding to the value of the duty ratio signal to the multiplexer 95. The operation of the selector circuit 93 will be described by using FIG. 3, which is an explanatory drawing of the controlling operation. FIG. 3 is a graph with the number of revolutions of the motor taken along the axis of abscissas and the DC voltage, the motor voltage, and the duty ratio taken along the axis of ordinates. The graph shows variations of the motor voltage, DC voltage, and duty ratio with respect to the number of revolutions under a constant load. At the time when the motor is rotated at a low speed as when it is started up, the selector circuit 93 outputs a switch signal to cause the DC voltage command value 1 to be selected and the DC voltage control circuit 9 controls the DC voltage to take on the selected DC voltage command value 1. Since the voltage is low in this state of the controlled DC voltage, the duty ratio reaches 100 % at an early stage of its increasing the rotating speed and, hence, it becomes unable to increase the number of revolutions of the motor any more (point A). At this point, the selector circuit 93 outputs a switch signal to select the DC voltage command value 2 to the multiplexer 95. The multiplexer 95 selects the DC voltage command value 2 and the DC voltage control circuit controls such that the DC voltage takes on the DC voltage command value 2. Thereby, the duty ratio is suddenly lowered to 60 %, while the motor voltage is increased. Although, in the case shown, the minimum value of the duty ratio is set to 60 %, this is a value used for convenience of explanation. In reality, depending on the load condition, the number of revolutions of the motor, the response speed of the speed control circuit 7, and the like, the duty ratio does not exhibit a sharp change. As the number of revolutions of the motor increases, the duty ratio becomes 100 % again (point B). Then, an operation as described above is performed again to select the DC voltage command value 3, whereby the DC voltage is increased and the duty ratio is lowered to 60 %. Through repetition of the above described operations, the DC voltage is increased with the increase in the number of revolutions and, thus, speed control of the motor can be executed. The case of decreasing the speed of the motor contrary to the above will be described below. when the number of revolutions of the motor is decreased upon incoming of a speed reducing command while the motor is rotating at a high speed, the duty ratio is decreased and the motor voltage is lowered. When the duty ratio becomes 60 % (point C), the DC voltage command value is switched from the DC voltage command value 4 to the DC voltage command value 3 contrary to the above and, thereby, the DC voltage is lowered. When the DC voltage is lowered, the duty ratio is increased to take on a value close to 100 %. Here, the decrease in the DC voltage must be set to such a value that will not cause the duty ratio to exceed 100 % when the DC voltage is lowered. To decrease the number of revolutions further, the duty ratio is decreased and the DC voltage command value is switched from the DC voltage command value 3 to the DC voltage command value 2 at the point B. By repeating such operations, the number of revolutions of the motor is controlled. Through repetition of the above described operations, the duty ratio is kept close to 100 % at all times and the motor voltage can also be kept close to the voltage required by the motor at all times. Thus, the conditions of the motor and the inverter can be improved in terms of losses incurring therein and the motor can be driven with the motor efficiency and the inverter efficiency kept in good conditions at all times. Further, as for the converter, the DC voltage need not be raised more than necessary and, hence, the converter efficiency can be improved. Further, since the DC voltage can be changed according to the number of revolutions of the motor, one single circuit can support motor rotation from a low speed to a high speed. In other words, even some kinds of motors different in their motor design points can be supported by one controller and operated anytime at the effective operating point. FIG. 4 is an explanatory drawing of controlling operations in the case where the switching points of the DC voltage are gathered at the side of higher number of revolutions than in the case shown in FIG. 3. Basic operations therein are the same as in the case of FIG. 3. The point different therefrom is that the values of the duty ratio at which the DC voltage is switched are set to 100 % and 90 %. Since a step-up chopper circuit is used in the converter circuit 2 and the DC voltage cannot be lowered below 2 times of the received voltage, the manner of operation shown in FIG. 4 is more effective in practical operations than that shown in FIG. 3. Further, although the converter circuit employing a step-up chopper circuit has been mentioned in the description of the present embodiment, the same operations can be performed even when a converter circuit employing an up/down chopper circuit or the like and capable of stepping down the DC voltage is used. In the foregoing, operations in the case of the selection levels of the DC voltage command values being four were described. However, it is possible to set up the DC voltage command values more finely. Further, since the DC voltage can be controlled in a wider range, it is better to increase the number of the selectable DC voltage command values as long as the circuit configuration permits. Although, in the case of the DC voltage control circuit shown in FIG. 2, the current command value is calculated from the deviation of the DC voltage, the DC voltage command value may be directly calculated. FIG. 5 is a diagram showing an internal structure of an embodiment of a DC voltage control circuit different from the DC voltage control circuit shown in FIG. 2. Its points different from FIG. 2 lie in a DC voltage command generator circuit 98 and a DC voltage detector circuit 97. In the system shown in FIG. 5, there is only one DC voltage command value and there are provided a plurality of detector circuits 97. Other circuits function the same as those in FIG. 2. In the case of FIG. 5, the multiplexer 95 is switched by a switch signal generated by the selector circuit 93 upon receipt of a duty ratio signal and, thereby, one of the plurality of the detector circuits is selected. According to the detection signal from the selected detector circuit, the DC voltage is controlled. Also in this system, operations shown in FIG. 3 and FIG. 4 can be performed and the same effects can be obtained. Here, the detector circuit 97 is a circuit for converting the DC voltage into a voltage level which can be treated by the control circuit and the circuit is configured such that it generates the voltage at the same level as the DC voltage command value when a predetermined DC voltage level is reached. Recently, many kinds of devices, such as converter circuit controlling IC, of the type in which the DC voltage is controlled through adjustment of the gain in the detector circuit have been produced. In motor controllers employing such a converter circuit controlling IC, the system as shown in FIG. 5 can be used effectively. FIG. 6 is a diagram showing the structure of FIG. 5 in a concrete circuit configuration. In FIG. 6, the selector circuit 93 shown in FIG. 5 is realized through software employing a microcomputer 70. Further, the proportional term 91 and integral term 92 shown in FIG. 5 are realized by an analog circuit employing an operational amplifier 71. The detector circuit 96 of the DC voltage is constructed by a resistor ladder circuit 72 as shown in FIG. 6. Here, the microcomputer 70 also has the functions of the speed detector circuit 5 and the speed control circuit 7 shown in FIG. 1. The DC voltage control circuits shown in FIG. 2, FIG. 5, and FIG. 6 were those performing DC voltage control through selection of the DC voltage command value or the DC voltage detection value by means of the multiplexer 95 or the like. In these systems, however, the command value or the detection value is switched over discontinuously. Hence, a great change in the DC voltage is produced at such a switching point. FIG. 7 shows the structure of the DC voltage control circuit employing a DC voltage command calculation circuit 90 for continuously varying the DC voltage command value 96 shown in FIG. 2. Further, FIG. 8 shows a case where the DC voltage detector circuit 97 shown in FIG. 5 is replaced with a DC voltage detection and calculation circuit 99. The DC voltage command calculation circuit 90 detects the duty ratio signal and calculates the DC voltage command value causing the duty ratio to take on a predetermined value. On the other hand, the DC voltage detection and calculation circuit 99 detects the duty ratio signal and calculates the DC voltage detection gain causing the duty ratio to take on a predetermined value and, then, outputs the DC voltage detection value in accordance with the detected gain. Through the described circuit configurations, the DC voltage command value or the DC voltage detection value becomes a continuous output and allows the DC voltage to be controlled linearly. FIG. 9 shows the DC voltage, duty ratio, and the motor voltage with respect to the number of revolutions obtained when the DC voltage control circuit shown in FIG. 7 or FIG. 8 is used. According to this system, the DC voltage can be linearly controlled and, hence, smooth motor control can be executed. Since the DC voltage can be controlled to become lower than the power source voltage when an up/down chopper circuit is used in the converter circuit 2 shown in FIG. 1, control with a large value of the duty ratio can be executed from the stage of low rotating speeds as shown in FIG. 10. Accordingly, it becomes possible to execute effective motor control even when the rotating speed is low. FIG. 10 shows relationships of the DC voltage, duty ratio, and the motor voltage to the number of revolutions when a converter capable of freely controlling the DC voltage is used. While the number of revolutions was taken along the axis of abscissas in the explanatory drawings of controlling operations shown in FIG. 3, FIG. 4, FIG. 9, and FIG. 10 above, similar graphs can be obtained even if the motor load or motor output is taken along the axis of abscissas. FIG. 11 shows a configuration of a DC voltage control circuit including a duty ratio control circuit formed of a duty ratio command value generator circuit 80, a proportional term 81, and an integral term 82 for linearly outputting the DC voltage command value like the circuit shown in FIG. 7. By using such a duty ratio control circuit, the DC voltage command value keeping the duty ratio constant can be calculated. Even when the DC voltage control circuit shown in FIG. 11 is used, operations like those shown in FIG. 9 and FIG. 10 can be performed. A configuration of a motor controller according to another embodiment of the invention will be shown in FIG. 12 and FIG. 13. FIG. 12 is an overall structural drawing of the motor controller and FIG. 13 is an internal structural drawing of the DC voltage control circuit 11 shown in FIG. 12. The different point of the present embodiment from the embodiment shown in FIG. 1 lies in the DC voltage control circuit 11, namely, in that the duty ratio signal and a speed deviation signal within the speed control circuit 12 shown in FIG. 12 are used for selection in the DC voltage detector circuit 97. operations of the selector circuit 110 shown in FIG. 13 will be described with reference to FIG. 3. The selector circuit 110, when the duty ratio has reached 100 % and the speed deviation is tending to increase the duty ratio still further, switches the output of the DC voltage detector circuit 97 to the side increasing the DC voltage. Conversely, when the duty ratio has lowered to 60 % and the speed deviation is tending to decrease the duty ratio still further, it switches the output of the DC voltage detector circuit 97 to the side decreasing the DC voltage. Thereby, the motor controller of the present embodiment operates as shown in FIG. 3. When the motor controller shown in FIG. 1 is used, since the selector circuit 93 takes only the duty ratio signal as the criterion of its selection, it would switch the DC voltage even when the motor load and motor output are balanced at the duty ratio of 100 % or 60 %. The present embodiment is such that is improved in view of the above described point. Namely, it detects, other than the duty ratio signal, a signal to detect whether the motor load and the motor output are balanced, a speed deviation signal in the present case, so as to prevent useless switching over of the DC voltage value. Although the speed deviation signal is detected in the present embodiment, another signal may be used provided that it indicates a balanced state between the motor load and the motor output. While, in the embodiment, the DC voltage detector circuit 97 is adapted to select one of the DC voltages, it may be adapted such that a plurality of DC voltage command values are provided and one DC voltage command value is selected therefrom. A motor controller according to still another embodiment of the invention will be described with reference to FIG. 14 and FIG. 15. FIG. 14 shows a DC voltage pulsation correcting motor controller which is formed of the motor controller shown in FIG. 1 and a DC voltage pulsation correcting circuit 10 added thereto. FIG. 15 is a drawing explanatory of the operation of the DC voltage pulsation correcting motor controller of FIG. 14. Each circuit of the DC voltage pulsation correcting motor controller shown in FIG. 14 operates the same as in the first embodiment shown in FIG. 1 except the DC voltage pulsation correcting circuit 10. The DC voltage pulsation correcting circuit 10 is such a circuit that detects pulsating components in the DC voltage and multiplies the duty ratio signal generated in the speed control circuit 7 by a pulsating signal of opposite phase to the detected pulsating components to thereby generate a correcting duty ratio signal. FIG. 15 shows changes with time of the duty ratio when the DC voltage pulsation correction was made. In FIG. 15, the axis of abscissas represents the time and the axis of ordinates represents the DC voltage, the duty ratio, and the correcting duty ratio. It is known that the correcting duty ratio is varying in the opposite phase to the pulsating components of the DC voltage. According to this embodiment, even if there exist pulsating components in the DC voltage, motor controlis not affected thereby and can be executed. In this system,however, the DC voltage control circuit 9 must be controlled with the duty ratio kept below 100 %. A configuration of an air conditioner controller to which the motor controller of the invention is applied is shown in FIG. 16. This embodiment is an inverter air conditioner detecting the room temperature and controlling the room temperature to be kept at a set temperature. The air conditioner controller comprises a room temperature sensor 203 for detecting the room temperature, a temperature control circuit 202 for calculating a rotation command value for a compressor 200 to bring the temperature deviation of the room temperature detection value from the room temperature setting value to zero, a compressor rotation control circuit 201 responsive to the rotation command for controlling the number of revolutions of the compressor 200, a refrigerating cycle control circuit 206 detecting the rotation command value and calculating and outputting control signals for controlling an outdoor fan 204, an indoor fan 210, and an expansion valve 208 constituting the refrigerating cycle, and control circuits (an outdoor air quantity control circuit 205, an indoor air quantity control circuit 209, and an expansion valve opening control circuit 207) responsive to the control signal from the refrigerating cycle controller 206 for controlling each of the constituents of the refrigerating cycle (the outdoor fan 204, the indoor fan 210, and the expansion valve 208). The compressor rotation control circuit 201 is a motor controller responsive to the rotation command value from the temperature control circuit 202 for controlling the speed of the motor directly coupled with the compressor, to which the motor controller of the above described embodiment is applied. The outdoor air quantity control circuit 205 and the indoor air quantity control circuit 209 are also constituted, like the compressor rotation control circuit 201, of motor controllers for controlling the speeds of the motors directly coupled with the outdoor fan and the indoor fan. Signals output from the refrigerating cycle control circuit 206 are rotation command signals for the indoor fan and the outdoor fan. The expansion valve opening control circuit 207 is directly coupled with the expansion valve 208 and the same is a controller of a step motor for regulating the opening of the expansion valve and generates a step signal in accordance with an opening signal output from the refrigerating cycle control circuit 206 to thereby drive the step motor. The expansion valve 208 is a motor-driven expansion valve whose expansion valve opening is changed in proportion to the angle of rotation of the step motor. The refrigerating cycle controller 206 calculates control signals for controlling the constituents of the refrigerating cycle (the outdoor fan 204, the indoor fan 210, and the expansion valve 208) such that the number-of-revolutions command value as the output of the temperature controller 202 becomes a preset value and outputs the number-of-revolutions commands and the opening command to the respective controllers. The control signals for the constituents of the refrigerating cycle are calculated such that the refrigerating cycle as a whole operates at the highest efficiency. The value of the number-of-revolutions command to be previously set in the refrigerating cycle control circuit 206 is changed according to operating conditions of the inverter air conditioner. By using the air conditioner controller of the embodiment, rotations of the compressor at excessively high speeds can be prevented and the service life of the compressor can be prolonged. Further, since the refrigerating cycle as a whole can be operated at the highest efficiency, cooling and heating capacity is improved and electric charges required for the operation can be saved. A configuration of a converter module according to an embodiment of the invention is shown in FIG. 17. This embodiment is a converter module obtained by having the converter circuit 2, the converter control circuit 8, and the DC voltage control circuit 9 described in the first embodiment integrally incorporated in a module. In this module, a step-up chopper is used. The converter circuit is formed of a rectifier circuit 101, a reactor 102, a transistor 104, a diode 103, and a smoothing capacitor 105, of which semiconductor devices of the rectifier circuit 101, transistor 104, and the diode 105 are modularized. The converter control circuit 106 has the same function as the converter control circuit 8 shown in FIG. 2 has. The selector circuit 108 selects one of the DC voltage values of the DC voltage detector circuit 107 in accordance with an external signal. Further, 110 selects one of the DC voltage command values of the DC voltage command circuit 109 in accordance with an external signal. By the present embodiment, a converter device capable of controlling DC voltage can be easily fabricated in a compact form. Industrial Applicability According to the motor controller of the invention, as described in the foregoing, it is possible to decrease losses incurring in the motor, inverter, and converter by the use of simple structures and to effectively run the controller. Further, since the DC voltage can be varied in accordance with the number of revolutions of the motor, one controller can support operation ranging from low speed operation to high speed operation. In other words, even several types of motors different in the motor design point can be controlled by one controller and operated at the point providing high efficiency at all times. Further, correction for the pulsation in the DC voltage can be easily carried out and stabilized motor speed control can be achieved. when the present motor controller is applied to an inverter air conditioner, highly efficient refrigerating cycle control can be performed and the electricity charges can be saved. Still further, by modularizing the converter circuit in the motor controller of the invention, a compact motor controller can be easily fabricated.

Claims: A motor controller comprising: a rectifier circuit (101) for converting AC power (1) to DC and comprising a smoothing circuit; a converter circuit (2) constituted of a chopper circuit (102-104) for controlling DC voltage by utilizing switching operation and inductance's energy storing effect; a motor drive device made up of an inverter circuit (3) connected to the output of said converter circuit and a motor (4); a converter control circuit (8) for controlling the switching operation of said chopper circuit; an inverter control circuit (6) for controlling the switching operation of said inverter circuit for driving said motor; a speed detector circuit (5) detecting the position of the rotor of said motor for calculating the speed of said motor; a speed control circuit (7) receiving said calculated speed value and a speed command value for performing speed control of said motor through said inverter control circuit; and a DC voltage control circuit (9, 11) receiving the output signal of said speed control cricuit (7) for controlling said DC voltage through said converter control circuit (8) in accordance with the output signal, characterized in that a DC voltage pulsation correcting circuit (10) is provided for detecting pulsating components of said DC voltage and for changing the input signal to the inverter control circuit (6) in accordance with the pulsating components. A motor controller according to claim 1, wherein said DC voltage control circuit (9), when the output of said speed control circuit (7) reaches a predetermined value, outputs a signal to cause said DC voltage to increase to said converter control circuit (8). A motor controller according to claim 1 to 2, wherein said DC voltage control circuit controls said DC voltage through said converter control circuit (8) such that the output of said speed control circuit takes on a predetermined value. A motor controller according to claim 1 to 2, wherein the output of said speed control circuit (7) is a duty ratio signal or a speed deviation signal of said calculated speed value from said speed command value. A motor controller according to claim 1 to 2, further comprising a DC voltage pulsation correcting circuit detecting pulsating components of said DC voltage for changing the input signal to said inverter control circuit in accordance with the pulsating components. A motor controller according to claim 1 to 2, wherein the speed control circuit (7) supplies said inverter control circuit with a duty ratio signal to cause the speed deviation to approach zero; and the DC voltage control circuit receives said duty ratio signal and includes a DC voltage command value generator circuit for generating a DC voltage command value and a DC voltage detector circuit for detecting the DC voltage corresponding to the output of said converter circuit, selecting the DC voltage command value or the DC voltage detection value so that said duty ratio signal takes on a value within a predetermined range, generating a current command value to cause the deviation of the DC voltage detection value from the DC voltage command value to approach zero, and outputting the current command value to said converter circuit. A motor controller according to claim 6, wherein said speed control circuit (7) further outputs said speed deviation and inputs the same to said DC voltage control circuit. A motor controller according to claim 6, wherein said DC voltage control circuit, when said duty ratio signal reaches the upper limit value or the lower limit value of said predetermined range, generates a current command value for increasing or decreasing said DC voltage. A motor controller according to claim 6, further comprising a DC voltage pulsation correcting circuit detecting pulsating components of said DC voltage, generating a correcting duty ratio signal by multiplying said duty ratio signal by a pulsating signal in opposite phase to said pulsating components, and inputting the same to said inverter control circuit. A motor controller according to claim 1 to 2, used in an inverter air conditioner comprising: a power factor improving converter circuit constituted of a step-up chopper circuit for controlling DC voltage and controlling the power factor of the power supply to be improved by utilizing switching operation and inductance's energy storing effect; a speed control circuit for controlling the speed of said motor by using said inverter control circuit in accordance with a speed command value coming from a temperature control circuit of said air conditioner, said inverter air conditioner comprising a DC voltage control circuit detecting the output signal of said speed control circuit for causing the DC voltage to rise when said output signal reaches a predetermined upper limit value and causing the DC voltage to fall when the output value reaches a predetermined lower limit value. An inverter air conditioner according to claim 10, wherein the output of said speed control circuit is a duty ratio signal. An inverter air conditioner according to claim 10 or 11 for controlling room temperature to a predetermined temperature by controlling the number of revolutions of the compressor and controlling variables of the refrigerating cycle such as opening of the expansion valve and air quantity of the heat exchanger, said inverter air conditioner detecting a number-of-revolution command value for the compressor and changing controlled variables of the refrigerating cycle such as opening of said expansion valve and air quantity of said heat exchanger in accordance with said number-of-revolution command value thereby achieving the room temperature control. A motor controller according to one of the claims 1 to 11, comprising a converter module made up of a rectifier circuit for converting AC to DC, of said chopper circuit, a switching device, and a diode, and a control circuit for controlling the DC voltage by controlling said switching device, said converter module comprising a plurality of detection terminals with different DC voltage detection gains, selecting one or more of said detection terminals in accordance with an external signal, and controlling the DC voltage in accordance with the detected value from the selected detection terminal. A motor controller according to one of the claims 1 to 11, comprising a converter module made up of a rectifier circuit for converting AC to DC, of said chopper circuit, a switching device, and a diode, and a control circuit for controlling the DC voltage by controlling said switching device, said converter module comprising a plurality of DC voltage command values, selecting one of said DC voltage command values in accordance with an external signal, and controlling the DC voltage in accordance with the selected DC voltage command value.

Inventors: ISHII MAKOTO, KAWABATA YUKIO, NOTOHARA YASUO, TAHARA KAZUO, TAKAKURA YUHACHI, ISHII, MAKOTO, KAWABATA, YUKIO, NOTOHARA, YASUO, TAHARA, KAZUO, TAKAKURA, YUHACHI
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1995
Main classification: H02P5
IPC codes: H02M5, H02P27