The servo system includes a servo drive and a servo motor. The drive uses precise feedback combined with a high-speed digital signal processor DSP to control the IGBT to generate a precise current output, which is used to drive the three-phase permanent magnet synchronous AC servo motor to achieve precise speed regulation and positioning functions. Compared with ordinary motors, AC servo drives have many protection functions inside, and the motors have no brushes and commutators, so the work is reliable and the maintenance and maintenance workload is relatively small.
In order to prolong the working life of the servo system, the following issues should be paid attention to during use. For the operating environment of the system, the five elements of temperature, humidity, dust, vibration and input voltage need to be considered. Regularly clean the heat dissipation and ventilation system of the numerical control device. Always check whether the cooling fans on the numerical control device are working properly. It should be inspected and cleaned every six months or a quarter depending on the environment of the workshop. When the CNC machine tool is not used for a long time, the CNC system should be maintained regularly.
First of all, the CNC system should be energized frequently, and let it run without load when the machine tool is locked. In the rainy season when the air humidity is relatively high, the electricity should be turned on every day, and the heat of the electrical components themselves should be used to drive away the moisture in the CNC cabinet to ensure the stable and reliable performance of the electronic components. Practice has proved that a machine tool that is often parked and not used is prone to various failures when it is turned on after a rainy day. Due to the working conditions of the end users of the motion control system and the limitation of the company’s first-line engineering technical support capabilities, the electromechanical system is often unable to obtain good equipment management, which can shorten the life cycle of mechatronics equipment, or reduce the production capacity due to equipment failure. Loss of economic benefits.
Servo driver is a kind of controller used to control servo motor. Its function is similar to that of frequency converter acting on ordinary AC motor. It is a part of servo system and is mainly used in high-precision positioning system. Generally, the servo motor is controlled through three methods of position, speed and torque to achieve high-precision transmission system positioning. It is currently a high-end product of transmission technology.
So how to test and repair the servo drive? Here are some methods:
1. When the oscilloscope checked the current monitoring output of the drive, it was found that it was all noise and could not be read
The cause of the fault: The output terminal of the current monitoring is not isolated from the AC power supply (transformer). Solution: You can use a DC voltmeter to detect and observe.
2. The motor runs faster in one direction than the other
Cause of failure: The phase of the brushless motor is wrong. Processing method: detect or find out the correct phase.
Cause of failure: When not used for testing, the test/deviation switch is in the test position. Solution: Turn the test/deviation switch to the deviation position.
Cause of failure: The position of the deviation potentiometer is incorrect. Treatment method: reset.
3. Motor stall
The cause of the fault: the polarity of the speed feedback is wrong.
Approach:
a. If possible, set the position feedback polarity switch to another position. (It is possible on some drives)
b. If using a tachometer, swap the TACH+ and TACH- on the drive to connect.
c. If an encoder is used, swap ENC A and ENC B on the drive.
d. In HALL speed mode, swap HALL-1 and HALL-3 on the drive, and then swap Motor-A and Motor-B.
The cause of the fault: the encoder power supply is de-energized when the encoder speed feedback.
Solution: Check the connection of the 5V encoder power supply. Ensure that the power supply can provide sufficient current. If using an external power supply, make sure that the voltage is to the driver signal ground.
4. The LED light is green, but the motor does not move
The cause of the fault: the motor in one or more directions is forbidden to move.
Solution: Check +INHIBIT and –INHIBIT ports.
Failure reason: The command signal is not to the drive signal ground.
Processing method: Connect the command signal ground to the driver signal ground.
5. After power-on, the driver’s LED light does not light up
Cause of failure: The power supply voltage is too low, less than the minimum voltage requirement.
Solution: Check and increase the power supply voltage.
6. When the motor rotates, the LED light flashes
Failure reason: HALL phase error.
Solution: Check whether the motor phase setting switch (60/120) is correct. Most brushless motors have a phase difference of 120°.
Failure reason: HALL sensor failure
Solution: Detect the voltages of Hall A, Hall B, and Hall C when the motor is rotating. The voltage value should be between 5VDC and 0.
7. The LED light always keeps red. Cause of failure: There is a failure.
Treatment method: Reason: overvoltage, undervoltage, short circuit, overheating, driver prohibited, HALL invalid.
Post time: Sep-02-2021
