Emerson Unidrive SP Error Code Inv OL

Emerson PLC & VFD Major Drive

Model: Unidrive SP | Code: Inv OL

Applicable Systems
Unidrive SP Commander SK EV2000 Mentor MP

Symptoms

The drive trips and displays Inv OL (Inverter Overload). The drive's internal overload protection has detected that the inverter output current has exceeded the drive's thermal overload curve for a sustained period. This indicates the drive itself is overloaded, not just the motor.

Possible Causes

  • Drive is undersized for the application (continuous current above rated)
  • Acceleration/deceleration cycle too frequent causing IGBT thermal buildup
  • Drive IGBT module degradation causing higher internal losses
  • Current detection circuit calibration drift causing false overload detection

Troubleshooting Steps

  1. Step 1: Measure the actual drive output current during normal operation
    Current should be at or below the drive's rated continuous current; if above, use a larger drive
  2. Step 2: Check the duty cycle of the application (frequent starts/stops)
    Reduce the frequency of acceleration/deceleration cycles or use a larger drive
  3. Step 3: Run the drive in no-load mode to check for abnormal internal current
    If Inv OL trips with no load, the IGBT module or current detection circuit is faulty
  4. Step 4: Inspect the IGBT module for signs of thermal stress (discoloration, bulging)
    If the module shows physical damage, it needs replacement

How to Reset

To reset: 1) Press RESET. 2) Reduce the load or duty cycle. 3) If the drive is undersized, replace with a larger one. 4) Restart. Caution: Repeated Inv OL trips indicate the drive is being operated beyond its capacity and will eventually fail.

Frequently Asked Questions

  • Q: What is the difference between O.L and Inv OL?

    O.L (Motor Overload) is based on the motor's thermal capacity - it trips when the motor would be damaged by overheating. Inv OL (Inverter Overload) is based on the drive's thermal capacity - it trips when the drive's IGBT modules would be damaged by overheating. They use different thermal models and thresholds.

  • Q: How do I size a drive correctly to avoid Inv OL?

    Select a drive whose rated continuous current is at least equal to the motor's rated current, and whose peak current capacity exceeds the motor's starting current requirement. For high-duty-cycle applications, select a drive one size larger than the minimum.

Related Emerson Fault Codes

Source: Emerson Control Techniques Unidrive SP Advanced User Guide, 2023

Category: PLC & VFD