JPH06133591A - Control circuit for compressor using three-phase induction motor - Google Patents

Abstract

PURPOSE:To detect the abnormality of a three-phase induction motor by detecting the duration of a current waveform higher than a prescribed threshold from the current flowing to a current sensor. CONSTITUTION:A peak detection circuit 13 detects the waveform of the current detected by means of a current sensor and finds the peak value of the waveform. A peak value slightly higher than the peak value of the rated current of a three-phase induction motor is set as a reference value in an abnormal current comparing section 15 and, when the peak value of the current waveform found by the circuit 13 becomes higher than the reference value, the section 15 continuously outputs an H-level signal while the peak value is higher than the reference value. When the H-level signal is outputted from the section 15, a timer section 16 is actuated and outputs an output signal after a specified period of time. Since a time comparing section 17 still receives the H-level signal from the abnormal current comparing section 15 when the timer section 16 outputs the output signal, the section 15 outputs an abnormality signal. Therefore, the abnormality of the three-phase induction motor, such as locking, nonstarting, etc., can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressor control circuit, and more particularly to a compressor control circuit for converting a voltage into a three-phase alternating current based on a direct current power source and controlling the rotation of the compressor through a three-phase induction motor. The present invention relates to a control circuit of a compressor using a three-phase induction motor, which detects disconnection, connection failure of the three-phase induction motor and abnormality of the control circuit of the compressor from the duration of the current peak value.

[0002]

2. Description of the Related Art An electric refrigerator installed in an automobile or the like uses a battery as a driving source to generate a three-phase AC voltage,
A three-phase induction motor drives the compressor to cool the electric refrigerator.

FIG. 3 shows a control circuit of a compressor using a conventional three-phase induction motor. In FIG. 3, 1 is a three-phase induction motor, 18 is a compressor, 3 is a battery, 4 is a stabilized power supply, and 5 is. An inverter unit, 6 is a control unit, 7 is a gate drive circuit, 8 is an analog-digital converter, and 9-1 to 9-3 are current sensors.

The DC voltage of the battery 3 is supplied to the inverter unit 5 and is converted into a three-phase AC voltage by the inverter unit 5 by the gate signals G1 to G6 output from the control unit 6 via the gate drive circuit 7. . This three-phase AC voltage is applied to the three-phase induction motor 1 to control the rotation of the compressor 18, but the current flowing in each phase of the three-phase induction motor 1 is detected by the current sensors 9-1 to 9-3. Therefore, the abnormality of the three-phase induction motor 1 is detected based on the increase / decrease in the average current detected by the current sensors 9-1 to 9-3.

[0005]

If the current sensors 9-1 to 9-3 are used for each phase as in the prior art, there is a drawback that the number of detection circuits is large and the cost thereof is high.

The present invention has been made in view of the above-mentioned drawbacks, and the inverter unit 5 when any one of the motor terminals U, V, W of the three-phase induction motor 1 is disconnected or one phase is disconnected. The input current waveform input to is as shown in Fig. 5,
The peak value of the three-phase induction motor 1 is larger than that in FIG. 4 when the motor is normal. Paying attention to the fact that this change in peak value changes relatively significantly as compared to the change in average current value, and by detecting this peak value, an abnormality of the three-phase induction motor 1 is detected. It is an object of the present invention to provide a control circuit for a compressor using the.

4 and 5 are measured under the same conditions, the vertical axis shows one major scale 5A, the horizontal axis shows one major scale 5ms, and CH2 represents the position of 0A (reference line). ing. That is, the peak value of the input current waveform at the time of one-phase disconnection in FIG. 5 is 22 A, and the peak value of the input current waveform at the normal time in FIG.
It is A.

[0008]

In order to achieve the above object, a control circuit of a compressor using a three-phase induction motor of the present invention is provided with an inverter circuit for converting a DC voltage into a three-phase AC voltage, and In the control circuit of the compressor using the three-phase induction motor, which is configured to control the electric power supplied to the three-phase induction motor through the inverter circuit and control the rotation of the compressor by the three-phase induction motor,
The three-phase induction motor of the three-phase induction motor includes The feature is that an abnormality is detected.

The abnormal time detecting means compares the peak value detected by the peak detection circuit with a peak detection circuit for detecting the peak value of the current waveform flowing through the current sensor at predetermined time intervals and the reference value. Is provided, an abnormal current comparison unit for outputting a predetermined time, a timer unit for generating a predetermined time, and a time comparison unit for comparing a duration output by the abnormal current comparison unit with a predetermined time generated by the timer unit are provided. An abnormality such as an induction motor lock is detected.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention.
In the figure, 1, 3 to 8 correspond to FIG. 3, and 2 is a rotary
A compressor, 11 is a shunt resistor as a current sensor, 12 is an amplifier circuit, 13 is a peak detection circuit, and 14 is an abnormality processing unit.

The shunt resistor 11 detects the current flowing through the inverter unit 5, and the detected current detected by the shunt resistor 11, that is, the current corresponding voltage, is appropriately amplified by the amplifier circuit 12. At this time, the noise component is removed by the CR of the resistor and the capacitor in the amplifier circuit 12. The detected current appropriately amplified by the amplifier circuit 12 is input to the peak detection circuit 13, the peak value of the detected current waveform is obtained, digitized by the analog-digital converter 8, and the abnormality processing section in the control section 6 is obtained. Enter in 14.

The abnormality processing unit 14 includes an abnormal current comparing unit 15, a timer unit 16, and a time comparing unit 17, as shown in FIG. 2, for example. The reference value of the abnormal current comparison unit 15 is set to a value slightly higher than the peak value of the three-phase induction motor 1 at the rated current, and the peak value of the detected current waveform detected by the peak detection circuit 13 is the reference value. When the value exceeds the limit, a signal is continuously output during the exceeding time, and, for example, an H level is output.

The timer unit 16 includes the abnormal current comparison unit 15 described above.
It operates when the H level is output from and outputs an output signal when a predetermined time elapses. The time comparison unit 17 outputs an abnormal signal when the output signal from the timer unit 16 is received and when the H level is output from the abnormal current comparison unit 15.

Now, when one phase is broken during operation of the three-phase induction motor 1 or when any one of U, V and W of the motor terminals is disconnected, the shunt resistor 11 is shown in FIG. Since the current waveform is detected, the peak detection circuit 13 detects the peak value. This peak value is digitized by the analog-digital converter 8 and input to the abnormal current comparison unit 15 in the control unit 6 and compared with the normal reference value.

The H level is output from the abnormal current comparing section 15, and the H level activates the timer section 16. The timer unit 16 sends a reset signal to the peak detection circuit 13 at regular time intervals to reset the peak detection circuit 13, but the three-phase induction motor 1 continuously outputs the current waveform of FIG. The current comparison unit 15 holds the H level. When the predetermined time generated by the timer unit 16 comes, the timer unit 16 outputs an output signal. When the timer section 16 outputs an output signal, the time comparison section 17 causes the abnormal current comparison section 1
Since it still receives the H level from 5, the abnormal current comparison unit 15 outputs an abnormal signal.

When the three-phase induction motor 1 is operating normally, a rush current flows and the abnormal current comparison unit 1
Although the H level is output from 5, the rush current disappears and becomes a steady current at the time when the output signal is generated from the timer unit 16, and the abnormal current comparison unit 15 is at the L level. No abnormal signal is generated from the time comparison unit 17.

On the other hand, even when the three-phase induction motor 1 is normal, when the start-up is defective, or when the motor is locked, a large current continues to flow in the shunt resistor 11, so that the time comparison unit 17 causes an abnormality. A signal is generated.

The abnormality processing section 14 is not limited to the one having the configuration shown in FIG.
The H level output from 5 is used as a gate, and the timer unit 1
Various configurations such as a configuration in which pulses from the pulse generation unit replaced with 6 are counted by a counter and an abnormal signal is output when the count value is a predetermined number or more are used.

The abnormality processing units 14 may be individually configured, but since they are the same as those in FIG. 3, the drive signals of the gate drive circuit 7 for driving the inverter unit 5 whose description is omitted will be described. It may be configured using a microcomputer to be created. Further, although the shunt resistor is used as the current sensor, various kinds of current sensors can be used for the same purpose.

[0020]

As described above, according to the present invention, the number of detecting points is only one, and a microcomputer can be used for a simple structure, and an abnormality such as a one-phase disconnection of a three-phase induction motor can be surely detected.

Further, it is possible to detect an abnormal state such as when the motor is locked or when the starting is defective, and the three-phase induction motor can be protected from these.

[Brief description of drawings]

FIG. 1 is a control configuration of an embodiment of a compressor using a three-phase induction motor of the present invention.

FIG. 2 is a configuration of an embodiment of an abnormality processing unit.

FIG. 3 is a control circuit diagram of a compressor using a conventional three-phase induction motor.

FIG. 4 is a current waveform diagram of one example in a normal state.

FIG. 5 is a current waveform diagram of one example when one-phase is disconnected.

[Explanation of symbols]

 1 Three-Phase Induction Motor 2 Rotary Compressor 3 Battery 4 Stabilized Power Supply 5 Inverter Section 6 Control Section 7 Gate Drive Circuit 8 Analog-Digital Converter 11 Shunt Resistor 13 Peak Detection Circuit 14 Abnormal Processing Section 15 Abnormal Current Comparison Section 16 Timer Section 17 hours comparison section

Claims (2)

[Claims] 1. An inverter circuit for converting a DC voltage into a three-phase AC voltage is provided, and electric power supplied to a three-phase induction motor is controlled through the inverter circuit, and rotation control of a compressor is performed by the three-phase induction motor. In a control circuit of a compressor using a three-phase induction motor configured to perform a current sensor that detects the input current of the inverter circuit and a current waveform that flows through the current sensor, a current waveform that is equal to or greater than a predetermined threshold value is maintained. A control circuit for a compressor using a three-phase induction motor, which is provided with an abnormal time detection means for detecting time and is adapted to detect an abnormality of the three-phase induction motor. 2. The abnormal time detection means compares a peak detection circuit that detects a peak value of a current waveform flowing through a current sensor at predetermined time intervals with a peak value detected by the peak detection circuit and a reference value. An abnormal current comparison unit that outputs when the high value is large, a timer unit that generates a predetermined time, and a time comparison unit that compares the duration output by the abnormal current comparison unit with the predetermined time generated by the timer unit, The control circuit for a compressor using a three-phase induction motor according to claim 1, wherein an abnormality of the phase induction motor is detected.