Common servo driver faults and solutions


The servo drive is a kind of controller used to control the servo motor. Its function is similar to that of the inverter acting on the common AC motor. It is part of the servo system and is mainly used in high-precision positioning systems. Generally, the servo motor is controlled by three modes: position, speed and torque to realize high-precision transmission system positioning. At present, it is a high-end product of transmission technology. The following are several methods for servo drive repair.

1. The LED light is green, but the motor does not work.

(1) Cause of malfunction: The motor in one or more directions is prohibited from operating.

Solution: Check the +INHIBIT and INHIBIT ports.

(2) Cause of failure: The command signal is not for the drive signal.

Processing method: connect the command signal ground and the driver signal ground.

2. After power-on, the LED of the driver is not lit.

Cause of failure: The supply voltage is too low, less than the minimum voltage requirement.

Treatment: Check and increase the supply voltage.

3. When the motor rotates, the LED light flashes.

(1) Cause of failure: HALL phase error.

Solution: Check if the motor phase setting switch is correct.

(2) Cause of failure: HALL sensor is faulty.

Treatment method: Detect the voltage of Hall A, Hall B, Hall C when the motor rotates. The voltage should be between 5 VDC and 0.

4. LED lights always keep red

Cause: There is a fault.

Solution: Cause: Overvoltage, undervoltage, short circuit, overheat, drive disable, HALL invalid.

5. motor stall

(1) Cause of failure: The polarity of the speed feedback is wrong.


a. If possible, turn the position feedback polarity switch to another position. (can be on some drives)

b. If using a tachometer, connect the TACH+ and TACH- on the drive.

c. If using an encoder, connect ENC A and ENC B on the drive.

d. In the HALL speed mode, reverse the HALL-1 and HALL-3 on the drive, and then connect the Motor-A and Motor-B pairs.

(2) Fault cause: The encoder power supply is de-energized when the encoder speed is fed back.

Solution: Check the power supply of the 5V encoder. Make sure that the power supply provides enough current. If an external power supply is used, make sure that the voltage is signaled to the driver.

6. the motor runs faster than the other direction in one direction

(1) Cause of failure: The phase of the brushless motor is wrong.

Treatment: Detect or find the correct phase.

(2) Cause of the fault: When not in the test, the test/deviation switch is in the test position.

Treatment method: Put the test/deviation switch in the deviation position.

(3) Cause of the fault: The position of the deviation potentiometer is incorrect.

Processing method: Reset.

7. When the oscilloscope checks the current monitoring output of the driver, it is found to be all noise and cannot be read.

Cause: The current monitoring output is not isolated from the AC power supply (transformer).

Treatment method: It can be observed with a DC voltmeter.

8. When the servo motor rotates at high speed, the motor deviation counter overflow error occurs. How to deal with it?

(1) Cause of failure: Motor deviation counter overflow error occurs at high speed rotation;

Solution: Check if the wiring of the motor power cable and the encoder cable is correct and the cable is damaged.

(2) Cause of fault: Motor deviation counter overflow error occurs when inputting a long command pulse


a. the gain setting is too large, re-adjust the gain manually or use the automatic adjustment gain function;

b. Extend the acceleration and deceleration time;

c. If the load is too heavy, it is necessary to re-select a larger capacity motor or reduce the load, and install a transmission mechanism such as a reducer to increase the load capacity.

(3) Fault cause: A motor deviation counter overflow error occurred during operation.


a. increase the deviation counter overflow level setting value;

b. slow down the rotation speed;

c. Extend the acceleration and deceleration time;

d. If the load is too heavy, it is necessary to re-select a larger capacity motor or reduce the load, and install a transmission mechanism such as a reducer to improve the load capacity.

9. The servo motor does not run when there is a pulse output. How to deal with it?

1) Monitor the current value of the pulse output of the controller and whether the pulse output lamp is blinking, confirm that the command pulse has been executed and the pulse has been output normally;

2) Check the controller to drive control cable, power cable, encoder cable for wiring errors, damage or poor contact;

3) Check if the brake of the servo motor with brake is open;

4) Monitor the panel of the servo drive to confirm whether the pulse command is input;

5) Run run command is normal;

6) Control mode must select the position control mode;

7) The input pulse type set by the servo drive is consistent with the setting of the command pulse;

8) Make sure that the forward side drive is prohibited, the reverse side drive inhibit signal and the deviation counter reset signal are not input, the load is released and the no-load operation is normal, and the mechanical system is checked.