JPH06205599A - Motor drive control circuit - Google Patents

Abstract

PURPOSE:To provide a motor drive control circuit capable of easily detecting the fault of the switching element of a switching circuit or the abnormality of motor winding by the circuit itself. CONSTITUTION:A motor drive control circuit, which has a rectifying circuit 4 for rectifying AC voltage and a switching circuit 9 for converting the output voltage of the rectifying circuit 4 into AC of specified frequency by the turning on and turning off of a plurality of transistors, is provided with the first current detecting circuits 11 and 12, which detects the input current to the rectifying circuit 4, and the second current detecting circuits 13 and 14, which detect the input current to the switching circuit. Furthermore, it is equipped with a means which detects the fault of the transistors and the abnormality of motor winding, based on the current detected by the first and second current detecting circuits, while turning on the transistors of the switching circuit in order.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive control circuit used in an air conditioner.

[0002]

2. Description of the Related Art In an air conditioner, the difference between the room temperature and the set temperature is detected as an air conditioning load, and the operating frequency of the compressor is controlled in accordance with the air conditioning load, so that an optimum air conditioning load can be accommodated. There are those that obtain the ability and improve the comfort and the energy saving effect. Such a variable capacity type air conditioner is equipped with a motor drive control circuit, a so-called inverter circuit, for drive control of the compressor motor.

This inverter circuit has a rectifying circuit for rectifying a commercial AC voltage, and a switching circuit for converting an output voltage of the rectifying circuit into an AC of a predetermined frequency by turning on / off a plurality of switching elements. The output of the inverter circuit is supplied to the compressor motor as drive power, and the compressor motor operates at a speed (rotation speed) according to the output frequency of the inverter circuit.

[0004]

A short circuit failure or an open failure may occur in the switching element of the inverter circuit. In this case, it becomes difficult to drive the motor properly. Another cause of inability to drive the motor properly is a short circuit or disconnection of the motor winding. This invention takes the above circumstances into consideration,

It is an object of a motor drive control circuit according to a first aspect of the present invention to provide a motor drive control circuit capable of easily detecting a failure of a switching element of a switching circuit by itself.

It is an object of a motor drive control circuit according to a second aspect of the present invention to provide a motor drive control circuit capable of easily detecting a failure of a switching element of a switching circuit and an abnormality of a motor winding by the circuit itself.

[0007]

According to a first aspect of the present invention, there is provided a motor drive control circuit for converting an output voltage of the rectifying circuit into an alternating current having a predetermined frequency by turning on and off a rectifying circuit for rectifying an alternating voltage and a plurality of switching elements. A motor drive control circuit that has a switching circuit that drives the motor at a predetermined speed by the output of the switching circuit, detects the input current to the switching circuit, and sequentially turns on the switching elements of the switching circuit. Means for detecting a failure of the switching element based on the detected current.

A motor drive control circuit according to a second aspect of the present invention has a rectifier circuit for rectifying an AC voltage, and a switching circuit for converting an output voltage of the rectifier circuit into an AC of a predetermined frequency by turning on / off a plurality of switching elements. In a motor drive control circuit that drives a motor at a predetermined speed by the output of the switching circuit, first current detection means for detecting an input current to the rectifier circuit and second current detection for detecting an input current to the switching circuit. And means for detecting a failure of the switching element and an abnormality of the motor winding based on the detection currents of the first and second current detection means while sequentially turning on the switching elements of the switching circuit.

[0009]

According to the first aspect of the motor drive control circuit, the failure of the switching element is detected based on the input current to the switching circuit while sequentially turning on the switching elements of the switching circuit.

According to another aspect of the motor drive control circuit, the switching elements of the switching circuit are sequentially turned on,
A failure of the switching element and an abnormality of the motor winding are detected based on the respective input currents to the rectifier circuit and the switching circuit.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. First, in the diagram showing the control configuration, a rectifier circuit 4 of a diode bridge is connected to a commercial AC power source 1 via a filter circuit 2 and a reactor 3, and smoothing capacitors 5 and 5 are connected to the output end of the rectifier circuit 4. . A smoothing capacitor 7 is connected to the smoothing capacitors 5 and 5 via a filter circuit 6, and a switching circuit 9 is connected to the smoothing capacitor 7 via a fuse 8. The motor 10 is connected to the switching circuit 9. Motor 10
Is a three-phase induction motor having three phase windings U, V, W, and is used, for example, as a compressor motor.

The switching circuit 9 includes a plurality of switching elements such as an NPN type giant transistor T.
u, Tv, Tw, Tx, Ty, Tz, of which transistors Tu, Tx have collector-emitter series circuits, transistors Tv, Ty have collector-emitter series circuits, and transistor T
Series circuits between the collector and emitter of w and Tz are connected in parallel, and windings U, V and W of the motor 10 are connected to the midpoints of these series circuits.

A current transformer 11 is provided on the connection line between the filter circuit 2 and the rectifier circuit 4, and the current transformer 1 is provided.
The detection circuit 12 is connected to 1. This detection circuit 12 is
The current transformer 11 constitutes the first current detecting means, and detects the input current (AC current) Ic to the rectifier circuit 4 from the AC voltage generated in the current transformer 11. A resistor 1 is connected to the connection line between the smoothing capacitor 7 and the switching circuit 9.
3 is inserted. The detection circuit 14 is connected to both ends of the resistor 13. The detection circuit 14 constitutes the second current detection means together with the resistor 13, and detects the input current (DC current) Id to the switching circuit 9 from the voltage across the resistor 13. Reference numeral 20 denotes a CPU which is a main control unit, and the CPU 20 includes a detection circuit 12, a detection circuit 14, and an operating device 2.
1, the display 22, and the driver 23 are connected.

The driver 23 has drive pulse signals Pu, Pv, P for the respective transistors of the switching circuit 9.
It outputs w, Px, Py, and Pz in the order and cycle according to the command from the CPU 20.

When the drive pulse signals Pv and Px are output, the transistors Tv and Tx are turned on and the exciting current flows through the windings V and U. When the drive pulse signals Pw and Py are output, the transistors Tw and Ty are turned on, and the exciting current flows through the windings W and V. When the drive pulse signals Pu and Pz are output, the transistors Tu and Tz are turned on and the windings U and W
Exciting current flows through. By repeating this, the motor 10 operates. The CPU 20 has the following main functional means. [1] Means for driving the switching circuit 9 in response to a command from the control unit of the air conditioner and causing the switching circuit 9 to output an AC voltage of a predetermined frequency.

[2] During operation, the detection current I of the detection circuit 14
When d abnormally rises above a predetermined value, for example 50 A, Id
A means for stopping the driving of the switching circuit 9 as a protection operation. This is to prevent transistor breakdown of the switching circuit 9.

[3] During operation, the detection current I of the detection circuit 12
A means for stopping the driving of the switching circuit 9 when c rises to a predetermined value. This is to prevent overcurrent input due to overload operation of the motor 10.

[4] When the failure detection mode is set by the operation device 21, the driver 23 sequentially outputs the drive pulse signal, and the switching circuit is based on the respective detection currents of the detection circuit 12 and the detection circuit 14 at that time. Means for detecting failure of each transistor of 9 and winding abnormality of the motor 10. Next, the operation will be described. First, a description will be given with reference to FIGS. 2 and 3.

When the failure detection mode is set by the operation unit 21, the driver 23 outputs several drive pulse signals Px, which causes the transistor Tx of the switching circuit 9.
Turns on repeatedly.

If the transistor Tu is normal, no change occurs, but if the transistor Tu has a short-circuit fault, a large current flows through the series circuit of the transistors Tu and Tx. This current is detected by the resistor 13 and the detection circuit 14 as the input current Id to the switching circuit 9. Since the detection current Id is as large as 50 A, the Id protection operation works. When the Id protection operation is activated, the CPU 20 determines the short-circuit failure of the transistor Tu. The determination result is displayed on the display 22.

If the transistor Tv has a short-circuit fault, a current flows through the transistor Tv, the winding V, the winding U, and the transistor Tx. This current is detected as the input current Id to the switching circuit 9 by the resistor 13 and the detection circuit 14, but is small as much as it passes through the windings V and U, and the Id protection operation does not work.

However, even if the Id protection operation does not work, the input current Ic to the rectifier circuit 4 gradually rises and is detected by the current transformer 11 and the detection circuit 12. This detection current Ic reaches about 10 A, at which time the CPU2
At 0, a short circuit fault of the transistor Tv or Tw is determined. The determination result is displayed on the display 22. The same determination is made for the short-circuit failure of the transistor Tw. Subsequently, several drive pulse signals Py are output, which causes the transistor Ty of the switching circuit 9 to be output.
Turns on repeatedly.

If the transistor Tv is normal, no change occurs, but if the transistor Tv has a short-circuit fault, a large current Id will flow through the series circuit of the transistors Tv and Ty. Since this current Id is as large as 50 A, the Id protection operation works. When the Id protection operation is activated, the CPU 20 determines the short-circuit failure of the transistor Tv. The determination result is displayed on the display 22.

If the transistor Tw has a short-circuit fault, a current Id flows through the transistor Tw, the winding w, the winding U, and the transistor Tx. This current Id is small as much as it passes through the windings W and U, and the Id protection operation does not work.

However, even if the Id protection operation does not work, the input current Ic to the rectifier circuit 4 gradually rises to 10 A.
When it reaches a certain level, the CPU 20 determines the short-circuit failure of the transistor Tw or Tu. The determination result is displayed on the display 22. Note that the transistor Tu
The same determination is made for the short-circuit failure of. Similarly,
The drive pulse signals Pz, Pu, Pv, and Pw are sequentially output every several shots, and failure detection is performed for all the transistors. When the output of one drive pulse signal is completed,
This time, two drive pulse signals are simultaneously output several times at a time. This is shown in FIGS. 4 and 5. The driver 23 outputs several driving pulse signals Pv and Px simultaneously, and the transistors Tv and Tx of the switching circuit 9 are repeatedly turned on at the same time.

If both windings V and U are short-circuited,
Transistor Tv, windings V and U, and transistor T
A large short circuit current instantaneously flows through x. This short circuit current is detected as the input current Id to the switching circuit 9. When the detected current Id is larger than the preset current value, the Id protection operation is activated. When the Id protection operation is activated, the CPU 20 determines that both the windings V and U are short-circuited. The determination result is displayed on the display 22.

If one of the windings V and U is broken, or if there is an open failure in one of the transistors Tv and Tx, the input current Id does not flow and the input current to the rectifier circuit 4 does not flow. Ic does not occur either. In this case, the CPU 20 determines that the winding V or U is broken or the transistors Tv and Tx have an open failure.
It is displayed on the display 22.

When only one of the windings V and U is short-circuited, the input current I is passed through one winding.
When the current value of c gradually increases and exceeds a preset current value, the CPU 20 determines that the winding short circuit has a failure, and the determination result is displayed on the display 22. continue,
The driving pulse signals Pw and Py are simultaneously output several times,
The transistors Tw and Ty of the switching circuit 9 are repeatedly turned on at the same time.

If both windings W and V are short-circuited,
Transistor Tw, windings W, V, and transistor T
A large short circuit current Id instantaneously flows through y. When this short circuit current Id is detected and is larger than the set current value, Id
Protective action works. When the Id protection operation is activated, the CPU 20 determines that the winding W or V is short-circuited. The determination result is displayed on the display 22.

If one of the windings W and V is broken or if there is an open failure in one of the transistors Tw and Tv, the input current Id does not flow and the input current to the rectifier circuit 4 does not flow. Ic does not occur either. In this case, the CPU 20 determines the disconnection of the winding W or V or the open failure of the transistors Tw and Tv,
It is displayed on the display 22.

When only one of the windings W and V is short-circuited, the input current I is passed through one winding.
When the current value of c gradually increases and exceeds a preset current value, the CPU 20 determines that the winding short circuit has a failure, and the determination result is displayed on the display 22.

Subsequently, the drive pulse signals Pu and Pz are simultaneously output several times, and the transistors Tu and Tz of the switching circuit 9 are repeatedly turned on at the same time. And the winding V,
As with U and windings W and V, failure detection and protection operations work.

As described above, the failure of each transistor of the switching circuit 9 and the winding abnormality of the motor 10 can be easily detected, so that the failure and the abnormality can be swiftly and appropriately dealt with. Therefore, the motor 10 can be driven in a proper state as much as possible.

[0034]

As described above, according to the present invention,

Since the motor drive control circuit according to the first aspect of the invention detects the failure of the switching element based on the input current to the switching circuit while sequentially turning on the switching elements of the switching circuit, the switching element of the switching circuit is switched. It is possible to provide a motor drive control circuit that can easily detect the failure of the above.

A motor drive control circuit according to a second aspect of the present invention detects the failure of the switching element and the abnormality of the motor winding based on the respective input currents to the rectifier circuit and the switching circuit while sequentially turning on the switching elements of the switching circuit. Since the configuration is adopted, it is possible to provide a motor drive control circuit capable of easily detecting a failure of a switching element of a switching circuit and an abnormality of a motor winding by the circuit itself.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a time chart for explaining the operation of the embodiment.

FIG. 4 is a flowchart for explaining the operation of the embodiment.

FIG. 5 is a time chart for explaining the operation of the same embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Commercial AC power supply, 4 ... Rectifier circuit, 9 ... Inverter circuit, 10 ... Motor, 11 ... Current transformer (first current detection means), 12 ... Detection circuit (first current detection means), 13 ...
Resistance (second current detection means), 14 ... Detection circuit (second current detection means), 20 ... CPU.

Claims (2)

[Claims] 1. A rectifying circuit for rectifying an AC voltage, and a switching circuit for converting an output voltage of the rectifying circuit into an AC of a predetermined frequency by turning on and off a plurality of switching elements. In the motor drive control circuit that drives the
Means for detecting an input current to the switching circuit,
A motor drive control circuit comprising: means for detecting a failure of the switching element based on the detected current while sequentially turning on the switching elements of the switching circuit. 2. A rectifier circuit for rectifying an AC voltage, and a switching circuit for converting an output voltage of the rectifier circuit into an AC of a predetermined frequency by turning on / off a plurality of switching elements. A motor is provided by the output of the switching circuit. In the motor drive control circuit that drives the
A first current detecting means for detecting an input current to the rectifying circuit, and a second current detecting means for detecting an input current to the switching circuit
Current detection means and means for detecting a failure of the switching element and an abnormal winding of the motor based on the detection currents of the first and second current detection means while sequentially turning on the switching elements of the switching circuit. A motor drive control circuit characterized by the above.