Applicable Systems
GA700
GA500
A1000
V1000
J1000
Symptoms
The drive trips. The digital operator displays GF, indicating a ground fault. The drive has detected that leakage current from one or more output phases to ground exceeds the threshold.
Possible Causes
- Motor cable insulation failure to ground
- Motor winding insulation failure to ground
- Moisture or water in the motor or junction box
- Cable gland or conduit fitting allowing water ingress
Troubleshooting Steps
- Step 1: Disconnect the motor cable and megger it to ground
Cable insulation resistance is in the megohm range - Step 2: Megger the motor windings to ground
Motor insulation resistance exceeds the minimum requirement - Step 3: Inspect motor junction box and cable glands for moisture or water
Junction box is dry and properly sealed - Step 4: Replace cables or motors with failed insulation
System operates without ground faults after replacement
How to Reset
To reset: 1) Fix the insulation failure (replace cable or motor). 2) Press RESET. Caution: Ground faults are safety hazards. Do not reset repeatedly without fixing the root cause. Inspect all motor cables and the motor.
Frequently Asked Questions
- Q: How does the drive detect a ground fault?
The drive measures the current in each output phase. If the vector sum of the three-phase currents is not zero, the difference represents ground leakage current. When this exceeds the threshold, the GF fault trips.
- Q: What insulation resistance is acceptable for a motor?
For 400V motors, IEEE 43 recommends insulation resistance above 100 megohm. Values below 1 megohm indicate severely degraded insulation that will cause ground faults. Use a 500V megohmmeter for testing.
Source: Yaskawa GA700 Technical Manual, 2023
Category: PLC & VFD