JPH0829470A - Detecting method for failure of current detector - Google Patents

Abstract

PURPOSE:To detect the failures of a current detector and an overcurrent detector before the normal operation of a motor. CONSTITUTION:In the drive circuit of an AC motor 7 which has a current detector, a main circuit is operated while being connected to the motor 7, and a predetermined current is passed through the motor 7 and it is determined whether or not a current value detected by the current detector 6 matches the current passed, so as to detect any failure of the current detector 6. In the drive circuit of the AC motor 7 which has an overcurrent detector 8 for detecting overcurrent on the basis of the magnitude of current flowing through the main circuit, an overcurrent of such magnitude as not damaging circuit elements is passed through the main circuit for a predetermined time, and it is determined whether or not the overcurrent detector 8 can detect the overcurrent, so as to detect any failure of the overcurrent detector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a failure of a current detector for controlling current in an AC motor control circuit or an overcurrent detector for detecting overcurrent.

[0002]

2. Description of the Related Art In a control circuit for an AC motor, a current detector is provided in order to stably perform speed control and the like and to perform current control which is an inner loop. If this current detector fails, the load current is not fed back, so the control system acts in the direction of increasing the load current, resulting in excessive current flow, resulting in abnormalities such as overcurrent and overload. Therefore, there is a problem that the motor and the main circuit are damaged. An overcurrent detector is provided to detect such an overcurrent.However, if this overcurrent detector has a failure, the same problem will occur. Etc. were detected.

[0003]

However, in the prior art as described above, the failure of the current detector or the overcurrent detector cannot be detected until the motor is normally operated, so that an excessive current flows in the main circuit. , Abnormal current flows,
There is a problem that the motor and the main circuit are damaged before the failure is detected or at the same time as the failure is detected. Therefore, the problem to be solved by the present invention is to detect the failure of the current detector or the overcurrent detector before the normal operation of the motor.

[0004]

In order to solve the above-mentioned problems, a method for detecting a failure of a current detector according to the present invention is a method of connecting a main circuit and a motor in a drive circuit of an AC motor having a current detector. The main circuit is operated, a predetermined current is passed through the motor, and it is determined whether the current value detected by the current detector is a current value commensurate with the passed current. The overcurrent detector failure detection method of the present invention is a method for detecting an overcurrent according to the magnitude of the current flowing in the main circuit, in a drive circuit of an AC motor having an overcurrent detector, which is applied to the main circuit for a predetermined time. An overcurrent having a magnitude that does not damage circuit elements is passed, and it is determined whether or not the overcurrent can be detected by the overcurrent detector.

[0005]

With the above means, a current is passed through the main circuit to detect a failure, so that the failure can be detected before the normal operation of the motor, and damage to the motor and the power section can be prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in the drawings. FIG. 1 is a configuration of an embodiment of the present invention, and FIG. 2 is a flowchart showing the operation. In FIG. 1, 1 is a thyristor, 2 is a main capacitor, 3 is a transistor, 4 is a microcomputer, 5 is a base drive circuit, 6 is a current detector, 7 is a motor, 8 is an overcurrent detector, and 9 is a current detection resistor. Reference numeral 10 is a regenerative resistor, and 11 is a regenerative transistor. In the circuit configured as described above, the current detector failure detection operation in the microcomputer 4 will be described with reference to the flowchart shown in FIG. First, in step 110, it is confirmed that the output value of the current detector 6 is 0 in the main circuit inoperative state (state in which no current is flowing). In step 120, the thyristor 1 charges a certain low voltage between the main circuit DC voltage PN (several tens V, though it depends on the motor resistance etc.). Next, in step 130, a certain positive current is input to the U phase and a certain negative current is input to the V phase of the current command of the current amplifier, and a current is passed from the U phase to the V phase. Then, if it operates normally, current feedback according to the command can be obtained, and this is confirmed by the current detector 6. When the operation is abnormal, the output of the current detector 6 becomes abnormal. In this case,
Since it is not possible to determine which is abnormal, U phase or V phase, other phases,
For example, a current is passed from the U phase to the W phase for determination. In step 140, as in step 130, a certain positive current is input to the V phase of the current command of the current amplifier and a negative current is input to the W phase,
Check the current by passing current from V phase to W phase. In step 150, as in step 130, a certain positive current is input to the W phase of the current command of the current amplifier, and a negative current is input to the U phase,
Check the current by passing current from W phase to U phase. In this way, it can be confirmed whether the current of the current detector 6 is 0, positive, or negative. It is also possible to determine which part of the current detector is out of order. The method of supplying the current to the current detector 6 may be other than the above-mentioned method, and in short, the current detector 6 can detect the current.

FIG. 3 is a flow chart showing an overcurrent detector failure detection operation in the microcomputer 4 in the circuit of FIG. First, in step 210, the thyristor 1 is ignited, the power is turned on, and the capacitor 2 is charged. Next, in step 220, the thyristor 1 is turned off, the regenerative transistor 4 is turned on for a certain time, the voltage of the capacitor 2 is discharged, and the voltage between PN is set to a certain low voltage. In step 230, the power transistor 3
Is ignited, a sufficient current is momentarily applied to the overcurrent detector 8,
Performs overcurrent detection operation. The flowing current should not exceed the maximum allowable current value of the power transistor 3. Next, in step 240, the operation of the overcurrent detector 8 is confirmed. When the overcurrent detector 8 operates, the overcurrent detector 8 is normal and does not operate, which means that the overcurrent detector 8 fails. Although the regenerative processing circuit is used in this example as a method for charging to a low voltage, it may be charged to a low voltage at the ignition timing of the thyristor 1. In the circuit configuration of FIG. 1, both the current detector 6 and the overcurrent detector 8 can be detected as faults, but if necessary, only one fault can be detected and the other can be omitted. it can.

[0008]

As described above, according to the present invention, the operation of the current detector or the overcurrent detector is confirmed before the motor is normally operated, so that the current detector or the overcurrent detector operates. It is possible to prevent damage to the motor and the power element that would otherwise occur.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration example for implementing a method of the present invention.

FIG. 2 is a flowchart showing a current detector failure detection operation.

FIG. 3 is a flowchart showing an overcurrent detector failure detection operation.

[Explanation of symbols]

1 thyristor, 2 main capacitor, 3 transistor, 4 microcomputer, 5 base drive circuit, 6 current detector, 7 motor, 8 overcurrent detector, 9 current detection resistor, 10 regeneration resistor, 11 regeneration transistor

Claims (2)

[Claims] 1. In a drive circuit for an AC motor having a current detector, the main circuit is operated while the main circuit and the motor are connected to each other, a predetermined current is passed through the motor, and the current is detected by the current detector. A failure detection method for a current detector, characterized in that a failure of the current detector is detected by determining whether or not the current value is a current value corresponding to the flowing current. 2. A drive circuit for an AC motor equipped with an overcurrent detector for detecting an overcurrent according to the magnitude of a current flowing through the main circuit, the drive circuit having a size that does not damage circuit elements in the main circuit for a predetermined time. A fault detection method for an overcurrent detector, characterized in that a fault of the overcurrent detector is detected by passing an overcurrent and determining whether or not the overcurrent can be detected by the overcurrent detector.