Inrush fault
Danfoss · VLT 2800 Variable Speed Drive
What does 35 mean?
This alarm appears when the adjustable frequency drive has been connected to the AC line supply too many times within a short period (1 minute). This typically indicates repeated power cycling that can stress internal components.
Common Causes
- Repeated power cycling (ON/OFF) of the AC line supply to the drive within a very short timeframe (e.g., manual switch, contactor chatter).
- External control system (PLC, relay) attempting to reset a temporary fault by cycling drive power instead of using a proper software reset command.
- Intermittent power supply issues causing brief power outages and immediate reapplication of AC voltage.
- Large capacitor banks or other high-inrush loads on the same AC line causing voltage sags that trigger protection circuits.
Repair Steps & Checklist
Click steps to track your progress.
- 1
Immediately cease all manual power cycling attempts of the drive's AC input supply.
- 2
Inspect the main input contactor (if present) for proper operation; check auxiliary contacts for reliability and ensuring it isn't chattering.
- 3
Review the control logic (PLC program, relay logic) that controls the drive's AC input power; ensure a minimum delay (e.g., 5 minutes) is implemented between power cycles.
- 4
Measure the AC line voltage at the drive's input terminals (L1, L2, L3) during operation to detect intermittent sags or drops using a logging multimeter.
- 5
Allow the drive's internal inrush current limiting circuit (e.g., precharge resistors) adequate time to cool and reset before reapplying power.
- 6
If an external circuit is used for power ON/OFF, ensure it provides a stable and continuous connection rather than repeated pulses.