Drive cooling fan
Common heat-related VFD and servo-drive failure point.
Danfoss VFD Fault E-Trip — What It Means
E-Trip on a Danfoss VFD (FC 200, FC 300, VLT series) indicates that an external trip signal has been activated on a digital input programmed as External Trip. Unlike drive-generated faults that detect internal electrical conditions, E-Trip is generated by an external device — a motor thermistor, a process safety switch, a PLC output, or another protective device connected to a designated digital input. The drive stops the motor and holds the fault until the external signal clears and the fault is reset.
Common Causes
- Motor thermistor activated — A PTC thermistor embedded in the motor windings has detected motor overtemperature and signaled the drive to trip. The motor is hot.
- External process safety switch opened — A pressure switch, flow switch, level sensor, or emergency stop device connected to the external trip input has opened, commanding the drive to stop.
- PLC output fault — The PLC or controller that manages the digital input is sending an unintended trip signal due to a program error, I/O fault, or communication loss.
- Wiring fault on the digital input — The wiring connected to the digital input programmed as External Trip has an open connection, pulling the input to a state that the drive interprets as a trip command.
Step-by-Step Fix
- Identify which digital input is programmed as External Trip — Navigate to the Danfoss parameter group 5-1x (Digital Inputs). Find the input set to function 27 (External Trip) or similar. Note the terminal number.
- Check the signal at that terminal — With power on and the drive tripped, use a multimeter to measure the voltage at the external trip digital input terminal. A 0V reading (when 24V is expected for run) means the external device has removed the enable signal.
- Trace the external device — Follow the wiring from the identified terminal to the connected device (thermistor, switch, PLC output). Identify what caused that device to change state.
- Check motor temperature — If a motor thermistor is the trip source, allow the motor to cool for 30–60 minutes. Check that motor ventilation is not blocked.
- Check external process switches — If a process switch (flow, pressure, level) tripped, investigate the process condition that caused it. Restore the process to normal before resetting the drive.
- Check PLC logic — If the external trip is PLC-controlled, review the ladder logic or program to confirm it is sending the correct signal under current operating conditions.
- Reset the fault — Once the external trip condition has been cleared (voltage restored to the digital input or thermistor cooled), reset the E-Trip fault via the keypad or a reset digital input and resume operation.
Parts Often Needed
| Part | Notes |
|---|---|
| Motor PTC thermistor | Replace if thermistor has failed short or open |
| Process switch (pressure/flow/level) | Replace if switch contacts have failed open |
| Terminal wiring | Re-terminate loose or broken wires at the drive control terminal block |
Need Replacement Parts?
Before ordering, match the drive part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If the external trip source cannot be identified or the process safety system is complex, consult the system integrator or a Danfoss-authorized technician. Never bypass an external trip input without fully understanding what protective function it serves.