Applicable Systems
EFC
FEX
FEI
HNC
Symptoms
The drive trips. The error display shows E-1008, indicating an output phase loss. The drive detects that one of the three motor output phases is not carrying current.
Possible Causes
- Motor cable disconnected or broken on one phase
- Loose terminal connection on one output phase
- Motor winding open circuit on one phase
- Drive output stage failure on one phase
Troubleshooting Steps
- Step 1: Inspect all motor cable connections at the drive and motor terminals
All connections are tight and making good contact - Step 2: Measure continuity of each motor cable conductor
All three phases show continuity - Step 3: Measure motor winding resistance on all three phases
Winding resistances are balanced - Step 4: If no external cause is found, the drive output may need service
Drive requires service if phase loss is internal
How to Reset
To reset: 1) Fix the disconnected or broken phase. 2) Clear the fault. Caution: A three-phase motor running with a missing phase overheats rapidly. The drive trips to protect the motor from damage.
Frequently Asked Questions
- Q: What damage can output phase loss cause?
A three-phase motor on two phases draws excessive current in the remaining phases, causing rapid overheating. Stator windings can burn out within minutes. The drive's phase loss protection prevents this.
- Q: How do I test for an open motor winding?
Measure resistance between each pair of motor terminals (U-V, V-W, U-W). All three readings should be nearly equal (within 5%). A significantly higher or infinite reading indicates an open winding.
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Source: Bosch Rexroth EFC Drive Manual, 2023
Category: PLC & VFD
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