The motor of servo driver is unstable, and the speed is fast and slow. The main reasons for this kind of fault are as follows:

1.The servo driver parameters are not adjusted properly, and the regulator does not reach the best working state.

2.The speed feedback signal is unstable due to interference and poor connection.

3.The tachogenerator is not installed properly, or the connection between the tachogenerator and the motor shaft is not good.

4.The carbon brush of servo motor is worn.

5.Local short circuit or short circuit to ground of armature winding.

6.The input voltage of the given speed is disturbed or poorly connected.