Applicable Systems
FC-302
FC-301
Symptoms
Danfoss VLT FC-302 drive reports warning during normal operation indicating drive system issue requiring diagnostic evaluation.
Possible Causes
- Motor thermal warning at 90% thermal capacity indicating approaching overload trip
- DC bus voltage high warning during regenerative operation approaching trip threshold
- Heatsink temperature approaching thermal trip level at 85 degrees C
- Motor phase current imbalance exceeding 5% between phases
Troubleshooting Steps
- Step 1: Read warning code on VLT FC-302 control panel LCP
Warning code and description shown on LCP display - Step 2: Check motor load and duty cycle
Motor load below 90% rated for continuous operation - Step 3: Inspect drive cooling fan and heatsink fins
Fan operating normally, heatsink fins clean and unobstructed - Step 4: Verify motor current balance on all three phases
Phase currents balanced within 3% of each other
How to Reset
Reset by: 1) Correct the condition. 2) Clear warning from LCP. 3) Run test. 4) Verify warning does not recur.
Common Replacement Parts
- FC302-CTL-01: Danfoss VLT FC-302 control card (Verify power size and voltage)
Frequently Asked Questions
- Q: What is the difference between a warning and an alarm?
A warning indicates an abnormal condition that the drive monitors but does not trip on. The drive continues to operate. An alarm causes the drive to trip and stop. Warnings should be investigated promptly to prevent escalation to alarms that stop operation.
Source: Danfoss VLT FC-302 Design Guide
Category: Electrical