The fault code FU210 appearing on a Sinic Electric servo drive indicates an output-to-ground short circuit. The main causes and solutions for an output-to-ground short circuit are as follows:

1. Drive power cable (UVW) shorted to ground:
Disconnect the motor cable and measure whether any of the drive's power cables (U, V, W) are shorted to ground (PE). Rewire or replace the drive power cable.

2. Motor shorted to ground:
Ensure the drive power cables and motor cables are securely connected. Measure the insulation resistance between the drive's U, V, W terminals and the ground wire (PE). The value should be at the megohm (MΩ) level. If not, replace the motor.

3. Drive fault:
If the fault persists after disconnecting the drive power cables from the servo drive and powering on multiple times, replace the servo drive.