Applicable Systems
FC-30
FC-51
FC-101
FC-202
FC-302
Symptoms
The drive trips. The display shows Alarm 9, indicating inverter overload. The drive output current has exceeded the rated overload limit for too long.
Possible Causes
- Load torque too high for the motor and drive capacity
- Motor undersized for the application
- Mechanical jam in the driven equipment
- Drive duty rating too low for the application
Troubleshooting Steps
- Step 1: Check the mechanical load for jams, binding, or excessive friction
Driven equipment moves freely without excessive resistance - Step 2: Verify motor and drive ratings match the load requirements
Motor power and drive current rating are adequate for the application - Step 3: Measure motor current during operation and compare to rated FLA
Motor current is at or below rated full load amps - Step 4: If the load is too high, increase motor and drive capacity
System operates within rated limits
How to Reset
To reset: 1) Remove the overload condition. 2) Allow the motor to cool. 3) Press RESET. Caution: Repeated overload trips cause thermal stress on motor windings. Ensure the system is properly sized.
Frequently Asked Questions
- Q: What is the overload rating of Danfoss FC-51?
The FC-51 has a normal duty overload of 110% for 60 seconds and 150% for 60 seconds in heavy duty, depending on the parameter setting. Check the specific model's datasheet for exact values.
- Q: What is the difference between normal duty and heavy duty?
Normal duty (also called variable torque) is for applications like fans and pumps with lower torque requirements. Heavy duty (constant torque) is for conveyors, cranes, and other high-torque applications. The drive overload capacity differs between the two.
Source: Danfoss VLT FC-51 Design Guide, 2023
Category: PLC & VFD