Lenze i500 Error Code Nmax

Lenze PLC & VFD Critical Speed

Model: i500 | Code: Nmax

Applicable Systems
i500

Symptoms

Overspeed. The motor speed has exceeded the maximum allowed speed. The drive immediately disables output toprotect the motor and driven equipment.

Possible Causes

  • Speed controller instability causing acceleration runaway
  • Encoder feedback signal lost while motor is coasting
  • Maximum speed parameter set too high
  • Overhauling load driving motor beyond commanded speed

Troubleshooting Steps

  1. Step 1: Check the equipment status and fault indicators to confirm the active fault code
    Fault indicator or HMI displays code Nmax as active
  2. Step 2: Verify all electrical connections, wiring harnesses, and connector seating
    All connections secure, no corrosion, loose pins, or damaged wires
  3. Step 3: Check encoder cable and connector at both motor and drive/controller ends
    Cable intact, connector fully seated, no bent or corroded pins
  4. Step 4: Verify encoder signal integrity with an oscilloscope if available
    Signal waveform normal with clean edges, no dropouts or noise
  5. Step 5: Check for mechanical interference, coupling slippage, or excessive load on the axis
    No mechanical interference, coupling secure, load within rated capacity
  6. Step 6: Verify the axis reference point and home position are valid
    Axis has valid reference point, position data is consistent
  7. Step 7: Replace encoder if signal is consistently absent or corrupted after cable checks
    New encoder provides stable, clean signal

How to Reset

To reset: 1) Identify and fix the root cause described in the fault symptoms. 2) Press RESET on the HMI or controller, or power-cycle the equipment. 3) If the fault recurs, contact manufacturer service. Caution: Document the fault code and context before resetting.

Frequently Asked Questions

  • Q: What does fault code Nmax mean on the Lenze i500?

    Fault Nmax indicates a position or encoder-related fault. The control system has detected an issue with axis positioning, speed feedback, or encoder signal. Check the encoder cable and motor feedback system.

  • Q: Can I continue operating the equipment with fault Nmax active?

    No. The equipment has detected a fault condition and has taken protective action (typically stopping or derating). Continuing to operate without fixing the root cause may cause further damage. Always investigate and fix the fault before resuming operation.

Related Lenze Fault Codes

Source: Lenze i500 Frequency Inverter Operating Instructions, Lenze Documentation

Category: PLC & VFD