JP2005094982A - Motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safe and highly reliable motor driver, by preventing an inverter current from being applied overcurrent and by keeping on rotating the motor, as long as there is a margin in a current value. <P>SOLUTION: When an absolute value of a detection voltage V(t) outputted from a rectifier circuit 18 is within the range of reference voltage values V1 to V2, the current value, supplied to the inverter circuit 14, is determined to be very high, so that motor speed is controlled in proportion to the absolute value of the detection voltage V(t). The speed of a motor 10 is reduced in matching with the ratio of decrease in the absolute value of the detection voltage V(t), whereas the speed of the motor 10 is increased in matching with the ratio of increase in the absolute value of the detection voltage V(t). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a motor drive device that converts DC power obtained by rectifying an AC power source into AC power and inverter-controls a motor such as a refrigerator or an air conditioner.

  2. Description of the Related Art In recent years, motor drives for household refrigerators and air conditioners have improved energy saving performance and noise / vibration performance by changing the motor frequency by an inverter circuit and changing the motor speed significantly.

2. Description of the Related Art Conventionally, as a motor driving device, there has been proposed a device that protects a driving device by stopping the inverter circuit when a supply voltage of a DC power supply circuit that supplies power to the inverter circuit falls below a reference value (Patent Document 1). ).
JP 2001-211683 A

  However, in the above drive device, when the voltage drops below the reference value, the inverter circuit stops. Therefore, it is desirable to avoid stopping the inverter circuit during operation as much as possible in devices that are continuously operated, such as refrigerators. The motor driving device is not suitable for use in a refrigerator or the like.

  Therefore, in view of the above problems, the present invention determines whether the motor is overloaded by detecting a decrease in the input voltage of the inverter circuit, and if it is overloaded, it is set according to the degree of the load. To provide a safe and highly reliable motor drive device by reducing the motor rotation speed and preventing the overcurrent from being applied to the inverter circuit, and at the same time keeping the motor running as long as there is a margin in the current value It is an object.

  The invention according to claim 1 drives a rectifier circuit connected to an AC power source, an inverter circuit that converts DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit, and the inverter circuit. A motor drive circuit comprising: a drive circuit; a power supply circuit that converts DC power of the rectifier circuit into a low voltage for control; and a rotation control circuit that controls the motor rotation by controlling the inverter circuit. Voltage detection means for detecting an input voltage of the circuit, and the detected voltage when the absolute value of the voltage detected by the voltage detection means is in a range between a first reference voltage value and a second reference voltage value set in advance. Voltage drop detecting means for controlling the rotation control circuit so that the rotational speed of the motor decreases in accordance with the rate at which the absolute value of the motor decreases. A drive apparatus for a motor according to claim.

  According to a second aspect of the present invention, the control circuit includes a first timer unit having an integration function, and the first timer unit includes an absolute value of a voltage detected by the voltage detection unit. Measuring the first integrated time when the value is within the range of the first reference voltage value and the second reference voltage value, and issuing a warning when the measured first integrated time T1 exceeds the set time. A motor driving apparatus according to claim 1.

  According to a third aspect of the present invention, the control circuit includes second timer means having an integration function, and the second timer means is configured so that the first timer means is counting the previous first integration time T1. In addition, the second integration when the absolute value of the voltage detected by the voltage detection means is in a range higher than the reference voltage value having the higher absolute value of the first reference voltage value and the second reference voltage value. 2. The motor according to claim 1, wherein a time T2 is measured, and the first integrated time of the first timer means is initialized when the measured second integrated time T2 exceeds a set time. It is a drive device.

  According to a fourth aspect of the present invention, the absolute value of the voltage detected by the voltage detection means while the second timer means is measuring the second integration time T2 is the first reference voltage value and the first reference voltage value. 2. The motor driving apparatus according to claim 1, wherein the second integrated time T <b> 2 is initialized when the voltage falls to a range of 2 reference voltage values.

  The invention according to claim 5 is the motor drive device according to claim 1, wherein the motor drive device is used as a motor drive device of a compressor of a refrigerator or an air conditioner.

  The motor drive device of the invention according to claim 1 can reduce the motor rotation speed, thereby suppressing the current value flowing through the switching element and preventing element destruction due to overcurrent or heat, and improving reliability. Can be made. Then, when the absolute value of the detected voltage drop detected by the voltage detection means is within a preset range between the first reference voltage value and the second reference voltage value (hereinafter referred to as a danger notification area), the voltage is reduced. Since the motor rotation speed is reduced proportionally, the motor rotation speed decreases proportionally even if the DC voltage decreases, so the current value supplied to the load is constant and is due to overcurrent. The element can be prevented from being destroyed, and the motor itself can be continuously driven without stopping, so that the reliability can be improved.

  According to a second aspect of the present invention, there is provided a motor drive device for measuring a first accumulated time, which is a total time of a danger notification area, by a first timer means. When the first accumulated time exceeds a set time, a buzzer is used. It is configured to warn by means such as light emitting diodes, and by continuing control close to the limit value, it can notify the user that the temperature rise of the heat sink and peripheral circuits is in a considerable state. , Reliability can be improved.

  In the motor drive device of the invention according to claim 3, when the absolute value of the voltage drop is higher than the set reference voltage value while the measurement by the first timer means is being performed, and the risk notification area is out, The measurement by the first timer means is interrupted, but the second accumulated time, which is the total time of the interruption, is measured by the second timer means. If the second accumulated time exceeds the set time, the voltage due to overload It is determined that the lowered state has been canceled, and the time counted by the first timer means is cleared and returned to the initial state. It is a device that does not shut off the power supply, such as an inverter of a refrigerator or an air conditioner Even if there is, the timer can be surely initialized.

  According to a fourth aspect of the present invention, there is provided a motor drive device in which a voltage drop caused by an overload occurs when the absolute value of the voltage drop enters a preset danger notification range while the measurement by the second timer means is performed. Is determined to be temporarily released but not completely released, and is configured to clear the time counted by the second timer means and return to the initial state. The circuit state can be reliably detected even when it becomes temporarily light and becomes overloaded again.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a block circuit diagram of a motor driving apparatus according to the present embodiment, and FIG. 2 is a flowchart showing a control operation of the driving apparatus.

(1) Configuration of Driving Device 12 for Motor 10 The driving device 12 for the motor 10 will be described with reference to FIG.

  The motor 10 is a three-phase brushless DC motor, and is a motor that drives a compressor of the refrigerator.

  The AC power supply 16 is connected to the rectifier circuit 18 and converts AC power into DC power. The output DC power of the rectifier circuit 18 is converted into three-phase AC power by the inverter circuit 52, and AC power is applied to the motor 18.

  The rectifier circuit 18 constitutes a voltage doubler rectifier circuit from the diode bridge 32 and the two electrolytic capacitors 30.

  The inverter circuit 14 is configured by an element such as an IPM (intelligent power module) or MOSFET in which six switching elements are contained in one package. Specifically, a three-phase bridge circuit is configured using six switching elements composed of diodes D1 to D6 connected in reverse parallel to the switching transistors Tr1 to Tr6, and a three-phase AC current is applied to the motor 18. The inverter circuit 14 generates three-phase AC power by controlling the conduction of the switching element according to the motor position detection signal by the control circuit 60.

  The control circuit 20 includes a power supply circuit 22 that converts DC power of the rectifier circuit 18 into a low voltage for control, a rotation control circuit 24, a drive circuit 34, and a voltage detection circuit 26 that detects an input voltage of the inverter circuit 14. The voltage drop detection circuit 28 detects a voltage drop abnormality based on a signal from the voltage detection circuit 26.

  The power supply circuit 22 converts the DC voltage of the capacitor 30 of the voltage doubler rectifier circuit into the DC low voltage of 5V or 12 to 15V of the control circuit 20, and includes a switching power supply and a low voltage IC.

  The voltage detection circuit 26 detects the DC voltage of the rectifier circuit 18 and divides the double voltage DC voltage with resistors 36 and 36 and outputs it to the voltage drop detection circuit 28 in addition to the A / D conversion input of the microcomputer. Is done.

  The voltage drop detection circuit 28 controls the output number of the motor by controlling the output signal of the rotation control circuit 24 when the absolute value of the input voltage of the inverter circuit 14 is within a predetermined range.

  The rotation control circuit 24 detects the three-phase drive currents Iu, Iv, and Iw output from the inverter circuit 14 to the three-phase stator winding of the motor 10 to detect the position and the number of rotations of the rotor. Then, feedback control is performed so that the detected rotational speed matches the speed command signal S input from the main control unit of the refrigerator, and the control signal is output to the drive circuit 34.

  The drive circuit 34 performs PWM control by outputting a PWM signal to the base terminals of the switching transistors Tr1 to Tr6 of the inverter circuit 14 according to a control signal from the rotation control circuit 24.

(2) Control Operation of Drive Device 12 The voltage drop detection circuit 28, the rotation control circuit 24, and the drive circuit 34 are realized by a microcomputer and its software, and the operation of the drive device 12 is described below based on the flowchart of FIG. Explain the contents.

  First, in FIG. 2, n is the total number of times that the detection voltage V (t) is within the preset reference voltages V1 to V2 when sampling is performed, and m is the detection voltage V similarly. (T) indicates the total number of times that last exceeded V1. N is the basis of the first integration time T1 integrated by the first timer means, and m is the basis of the second integration time T2 integrated by the second timer means. Note that the absolute value of V1> the absolute value of V2.

  In step 1, n = 0 and m = 0 are initialized.

  In step 2, the sampling time Δt is measured.

  In Step 3, it is determined whether or not the absolute value of the detection voltage V (t) is in the region of V1 to V2 after the sampling time Δt has elapsed. Here, V (t)> V1 or more is a safety area, V1> = V (t)> = V2 is a danger notification area, and V2> V (t) is a danger area.

  In step 4, as shown in FIG. 3, when the absolute value of the detection voltage V (t) is in the danger notification region of the reference voltage values V1 to V2, the current value supplied to the inverter circuit 14 is considerably high. Therefore, the rotational speed of the motor is controlled in proportion to the absolute value of the detection voltage V (t). The control reduces the rotation speed of the motor 10 in accordance with the rate at which the absolute value of the detection voltage V (t) decreases, and conversely, the motor 10 in accordance with the rate at which the absolute value of the detection voltage V (t) increases. Increase the number of revolutions. The reason for this is that when the motor 10 is rotating at a constant torque, the consumed power value is constant, but when the DC voltage of the rectifier circuit 18 decreases, the motor 10 tries to obtain a constant amount of power. Will be increased. If the current value is too small, the undesired state such as heat generation in the inverter circuit 14 or deterioration of the switching element is caused. Therefore, when the DC voltage decreases, the rotational speed of the motor 10 is decreased in accordance with the decrease rate. If the rotational speed of the motor 10 decreases, the power consumption decreases accordingly, so that the current value flowing through the motor 10 becomes constant. As a result, the burden on the inverter circuit 14 is reduced, and although the rotation speed of the motor 10 itself decreases, the rotation of the motor 10 continues and the reliability of the device increases.

  In step 5, n is incremented. Also, m = 0 is initialized. The initialization of m corresponds to the initialization of the second integration time T2 described later.

  In step 6, T1 = n × Δt obtained by multiplying the incremented value n and the sampling time Δt is the first integrated time T1 that is the total time that the detection voltage V (t) was in the danger notification area. When it is determined that the first integrated time T1 is longer than the preset set time, it is determined that the refrigerator is in an unfavorable state. The function of the first timer means is to measure the first integrated time T1.

  In step 6, the user of the refrigerator is notified by means such as a buzzer or a lamp. In this operation, even when the detection voltage V (t) temporarily becomes higher than V1 due to noise or the like, since the previous value of n is held, highly reliable control can be performed.

  On the other hand, in step 8, as shown in FIG. 3, when the detection voltage V (t) exceeds V1 and becomes a safe region in a stable state for reasons such as load reduction, m is increased every Δt. Incremented.

  In step 9, a second integrated time T2 that is an elapsed time from the timing at which the detected voltage V (t) has finally exceeded V1 is calculated by T2 = Δt × m. The function of the second timer means is to measure the second integrated time T2.

  When the second integrated time T2 is longer than the preset set time, in step 10, the motor 10 is regarded as having entered a completely stable state, and the value of n counted previously is initialized. Note that once the detection voltage V (t) returns to the danger notification range, m is initialized in step 5 and it is not determined that the stable state has been reached, so the refrigerator can be reliably protected. .

  As a result, the counter can be initialized even in a device such as a refrigerator that does not shut off the power supply in general use.

  The motor drive device of the present invention is preferably used for a compressor motor of a refrigerator or an air conditioner.

It is a block diagram of the drive device of the motor of one embodiment of the present invention. It is a flowchart which shows control of the drive device of a motor. It is a time chart of detection voltage V (t).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 12 Drive apparatus 14 Inverter circuit 16 AC power supply 18 Rectifier circuit 20 Control circuit 22 Power supply circuit 24 Rotation control circuit 26 Voltage detection circuit 28 Voltage drop detection circuit 30 Electrolytic capacitor 34 Drive circuit

Claims (5)

A rectifier circuit connected to an AC power source;
An inverter circuit for converting DC power of the rectifier circuit into AC power;
A motor driven by the inverter circuit;
A drive circuit for driving the inverter circuit;
A power supply circuit that converts the DC power of the rectifier circuit into a low voltage for control;
A rotation control circuit for controlling the motor circuit by controlling the inverter circuit;
In a motor drive circuit having
Voltage detection means for detecting an input voltage of the inverter circuit;
When the absolute value of the voltage detected by the voltage detecting means is in a range between a first reference voltage value and a second reference voltage value set in advance, the motor is adjusted in accordance with the rate at which the absolute value of the detected voltage decreases. Voltage drop detection means for controlling the rotation control circuit so that the number of rotations decreases,
The motor drive device characterized by having. The control circuit includes first timer means having an integration function,
The first timer means includes
The first timer means measures a first integration time when the absolute value of the voltage detected by the voltage detection means is in a range between the first reference voltage value and the second reference voltage value;
The motor driving device according to claim 1, wherein a warning is given when the measured first accumulated time T1 exceeds a set time. The control circuit has a second timer means having an integration function,
The second timer means includes
While the first timer means is counting the previous first integration time T1, the absolute value of the voltage detected by the voltage detection means is the absolute value of the first reference voltage value and the second reference voltage value. Measure the second accumulated time T2 when it is in a range higher than the higher reference voltage value,
2. The motor driving device according to claim 1, wherein when the measured second accumulated time T <b> 2 exceeds a set time, the first accumulated time of the first timer unit is initialized. 3. The second timer means includes
When the absolute value of the voltage detected by the voltage detection means falls to the range between the first reference voltage value and the second reference voltage value while measuring the second integration time T2, the second integration time 2. The motor driving apparatus according to claim 1, wherein time T2 is initialized. The motor driving device according to claim 1, wherein the motor driving device is used as a motor driving device for a compressor of a refrigerator or an air conditioner.

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