Common Variable Speed Drive (VSD) Trips

This page provides an overview of the most common trips experienced when using a Variable Speed Drive (VSD). All VSDs have in-built protection to ensure the drive operates within its limits.

If your VSD is tripping, it indicates a problem that requires attention. Repeatedly resetting and restarting without addressing the cause may lead to failure.

If your VSD is tripping, start by identifying when the trip occurs (start-up, running, or stopping), then refer to the relevant section below.



You can navigate the trips using the list below, or scroll to browse all topics.

This page is intended as a general guide for all VSDs, so specific trip codes are not shown, as these vary between manufacturers and product ranges. Product-specific trip codes and keypad displays will be covered on the relevant VSD range pages.

Additional Help and Guidance pages:

Overcurrent - High Overload

  • An overcurrent trip occurs when the detected current level is significantly higher than the VSD rating.
  • Overcurrent is common and can cause significant damage if not addressed.
  • It is helpful to know when the trip occurred, as this can help determine the cause.

Common Causes – At Start-up

  1. Incorrect wiring
  2. Insecure wiring
  3. Broken cables
  4. Motor winding fault
  5. Motor brake not releasing
  6. Inverter hardware fault

Quick Check: Ensure any motor brake is not connected to the VSD output, as it will not release. A separate supply will be required.

Common Causes – Whilst Running

  1. Acceleration time too short
  2. Excessive load
  3. Shock load
  4. Incorrect parameters

Quick Check: Ensure the motor is rotating in the correct direction. Incorrect rotation can lead to excessive load.

Helpful Tips:

  • Some VSDs include a parameter to set the maximum current. Default values vary between manufacturers and should be reviewed.
  • For new applications, excessive load may be due to incorrect motor selection.
  • Overspeed requires careful consideration, especially for fan or pump loads.

Overcurrent - Thermal (I²t)

  • A thermal overcurrent trip occurs when the current exceeds the VSD rating for an extended period.
  • This is a common fault and can cause significant damage if not addressed.
  • It is helpful to know when the trip occurred, as this helps determine the root cause.

Common Causes

  1. Continuous excessive load
  2. Fluctuating load conditions
  3. Part of the duty cycle has an excessive load

Quick Check: If the VSD is dual-rated, ensure the correct rating has been selected.

Helpful Tips:

  • Parameters associated with dual rating are often located in the main menu.
  • Check the mains input voltage. Low voltage will result in higher current draw for the same kW output.
  • For reciprocating loads, increasing the overload setting may help, but proceed with caution.

Overcurrent - Motor

  • A motor overload trip occurs when the motor rated current is exceeded for an extended period.
  • The motor rated current should be set correctly using the motor nameplate.
  • Some VSDs monitor speed alongside current to prevent overheating at low speeds.

Common Causes

  1. Incorrect motor nameplate data
  2. Load beyond the rating of the motor (but not the VSD)
  3. High load at low speed for extended periods

Quick Check: Ensure the motor connections match the required voltage (Delta = lower voltage, Star = higher voltage).

Helpful Tips:

  • Motor thermistors or thermocouples can be used on most VSDs to detect overheating.
  • Ensure the correct current rating is used (Star vs Delta confusion is common).
  • For spindle motors, ensure the motor frequency is correctly entered (this differs from the maximum VSD frequency).

Over Voltage

  • An overvoltage trip occurs when the DC link voltage exceeds a fixed internal limit.
  • If the load is over hauled the motor will become a generator and the power will go into the VSD.
  • The default limit is determined by the VSD rating but can sometimes be adjusted.
  • For high inertia loads, use a VSD with a braking chopper (DBr).

Common Causes

  1. Very short deceleration times on a high interia load.
  2. Incorrect braking resistor selection
  3. Braking resistor resistance too high
  4. An idling fan can generate voltage when the VSD is connected but not running

Quick Check: Ensure the dynamic braking function is enabled if required.

Helpful Tips:

  • Brake resistors are not universally interchangeable—always check compatibility.
  • Some VSDs automatically extend deceleration time to prevent trips.
  • You can set stopping mode to "Coast to Stop" to avoid regeneration.

Over Temperature

  • An overtemperature trip occurs when the internal temperature exceeds a fixed limit.
  • High temperatures reduce VSD lifespan.
  • Proper airflow and fan operation are essential.

Common Causes

  1. Cooling fans not working
  2. Insufficient clearance
  3. Poor panel airflow
  4. High ambient temperature

Quick Check: Check enclosure filters are clean.

Helpful Tips:

  • High IP enclosures can trap heat.
  • Forced ventilation is often required on the control cabinet.
  • Natural ventilation requires careful design, as the VSD is a heat source.

Under Voltage

  • An undervoltage trip occurs when the DC link voltage falls below a fixed level.
  • This often occurs during normal power-down.
  • It can mask previous faults in VSD fault logs.

Common Causes

  1. Normal power-down
  2. Blown fuse
  3. Incorrect supply voltage
  4. Incorrect input wiring

Quick Check: Allow time for full power-down before diagnosing.

Helpful Tips:

  • Check DC bus voltage (~1.35 × mains voltage). This is only possible if the DC+ and DC- terminals are available (not the braking resistor terminals).
  • Verify the drive voltage rating.
  • Ensure all terminals are tight.

RCD Trip

  • An external RCD may trip when the VSD is powered up
  • This is a common issue and is usually easy to resolve
  • This typically occurs at power-up but may also happen during operation

Common Cause

  1. The EMC filter inside the VSD contains capacitors connected to earth. These can create leakage currents that may cause a standard RCD to trip, even though the unit is operating safely.

Quick Check: Check whether the EMC earth connection can be removed. This is possible on many VSDs, but not all models.

Helpful Tips

  • The capacitors connected to earth conduct high-frequency leakage currents, which standard RCDs may interpret as a fault condition.
  • Removing the EMC earth connection disables part of the EMC filter and may increase electromagnetic interference (EMI).
  • If EMC performance is required, a Type B RCD can be used.
  • Type B RCDs are more expensive than standard types.
  • Interference after removing the EMC earth connection is uncommon but possible.
  • Removing the EMC earth connection does not affect basic electrical safety but may affect EMC compliance.

Additional Information

Variable Speed Drives (VSDs) are highly reliable and widely used in critical applications. Most trips are caused by external factors such as incorrect setup, application issues, or installation problems.

Always review all recorded faults, as the keypad may only display the first. Some manufacturers also provide alarm logs which can assist in diagnosis.

This page is intended as a general guide for all VSDs, so specific trip codes are not shown, as these vary between manufacturers and product ranges. Product-specific trip codes and keypad displays will be covered on the relevant VSD range pages.

Created by Inverter Drive Supermarket Ltd. Last reviewed April 2026