What causes a VFD to trip

What causes a VFD to trip? Keeping a VFD clean, cool, and dry is important, but it’s not always enough. Even well-installed drives can suddenly stop, leading to unplanned downtime and costly interruptions. In this guide, we’ll break down the main VFD trip reason, explain the most common failures, and provide practical, engineer-tested solutions to help you keep your operations running smoothly.

What Does Trip Mean in a VFD

A trip in the context of a Variable Frequency Drive (VFD)  refers to the automatic shutdown of the drive when an abnormal condition or malfunction is detected. This shutdown is not a failure of the VFD, it is a built-in protective function designed to safeguard the drive, the motor, and the connected system from damage.

The VFD continuously monitors several critical parameters, including:

• Motor speed
• Temperature
• Voltage
• Current

What causes a VFD to trip

Unexpected VFD tripping can lead to equipment damage, process interruptions, and higher maintenance costs. If you’re wondering what causes a VFD to trip, the most common reasons include overcurrent, overvoltage, under voltage, overheating, ground faults, and motor or load-related problems.

To avoid these issues, it’s important to understand the detailed causes of VFD failure and learn how to identify and correct them before they lead to costly downtime.

The Main Causes of VFD Failure and How to Spot and Avoid Expensive Issues:

• Accumulation:

This mostly refers to “gunk,” which is composed of dust mixed with ordinary plant air, which typically contains moisture, oil, and metal particles. When it comes to what causes a VFD to trip, accumulation is one of the most common reasons.

Furthermore, it’s not the dirt itself.  It’s because the buildup of dirt and dust attracts moisture and prevents adequate airflow.  In addition to producing extra heat, the metallic particles may cause your circuit boards to develop stray current channels. These combined effects degrade VFD performance and may eventually lead to complete failure.

•  Too Much Heat

  As was previously said, accumulation is typically the cause of excess heat.  However, weak connections and/or current levels over the drive’s rated level might also result in excessive heat.  Visual inspection of the connections is possible, although a temperature probe or portable digital pyrometer could be needed.

  Never let the connections get hotter than the wires that link them.  It’s also advisable to check the temperatures of the drive and motor. Capacitors and other parts may blow as a result of overheating.  Additionally, it can result in short circuits, which might not be sufficient to trip an overload or blow a fuse, but they could be enough to stop the controller and leave you wondering why production stopped.

• Condensation and Moisture

For many plants, moisture or condensation is a typical issue. Your devices’ circuit boards may corrode as a result of excessive dampness.  When a VFD is operating continuously, the heatsink usually produces enough heat to prevent moisture within.   You may need to take precautions against condensation if you operate yours less frequently.

• • • Damaged components or loose connection

    Loose connections and damaged or aging components are probably the reasons behind your VFD’s inconsistent performance. Common reasons for loose connections that might result in hazardous arcing include vibration and heat cycles. Overcurrent problems and other component damage can result from arcing at the output.

    • Making Use of the Incorrect Machine or Motor

    Using the incorrect machine or motor may not cause immediate issues, but problems are almost guaranteed to arise over time. If the connected equipment draws more power than the drive is designed to handle, the VFD can overheat and eventually trip.

• Elevated Bus Failure

This is a typical VFD flaw.  It is typically brought on by outside variables, such as an abrupt increase in the AC line voltage or an overhauling load created by the machine’s inertia.  The VFD takes precautionary action because the load keeps rotating faster than the motor’s suggested speed. 

Common Types of VFD Trips

• • • • • Voltage-Source Inverter Drives:

        The most common type of variable frequency drive available on the market is the voltage-source
        inverter (VSI) drive. They are made up of a DC link, a rectifier that changes AC into DC, and an
        inverter that changes DC back into AC. To precisely manage the motor’s speed and torque, the inverter section employs pulse width modulation (PWM) to regulate the frequency and voltage delivered to the motor.

        • • Inverter Drives with Current Sources:

      The second of the three categories of variable frequency drives is current-source inverter (CSI)
      drives. These drives make use of an inverter, a DC connector, and a rectifier. Rives are the second. 

      • Drives with Direct Torque Control:

      The most regulated variable frequency drive is a direct torque control (DTC) drive. A variable frequency control step is not necessary since DTC technology instantaneously monitors and regulates motor torque and flux.
      Faster dynamic reactions, less torque ripple, and improved precision are the outcomes.

    • 

How to Fix VFD Tripping Issues

1- Visually examine the DC Bus Capacitors:

To diagnose a capacitor malfunction, you must visually examine the DC Bus Capacitors for damage indicators such as a cracked or deformed case or a popped-out pressure plug, which might point to an electrolyte problem.

2- Check the resistance across the capacitors:

Next, check to see if the resistance across the capacitors is as advised by using an oscilloscope.

3- Perform internal tests beyond the capacitors:

When troubleshooting your VFD, you should do the following internal tests in addition to identifying and fixing the previously listed issues.

Read about: VFD tripping on overcurrent

Preventive Measures to Avoid VFD Tripping

To avoid frequent VFD trips, follow these preventive measures:

1. Assure correct installation.
2. Perform routine maintenance.
3. Take care of any issues, including voltage swings, overheating, and loose connections, to stop variable frequency drives (VFDs) from tripping.
4. Examine and clean the VFD regularly.
5. Keep an eye out for moisture and dust.
6. Make that the VFD is appropriate for the load and motor.

 When and How to Safely Reset a VFD After Tripping

1-Steps to Identify the Cause:

1. Fault Codes: The cause of the trip is usually indicated by a fault code that VFDs show.  Visual Examination:
2. Examine the area around the VFD and motor for any indications of physical damage, overheating, or strange odors.
3. Examine the logs: If the VFD is capable of recording data, look through the logs to see any trends or incidents that occurred before the trip.
4. Typical Reasons for Trips: Common causes include motor or load problems, overcurrent, undervoltage, and overheating.

2-Power Cycle: Cut Power:

1. Turn off the relevant circuit breaker to cut off the VFD’s power.
2. Wait for Discharge: Follow the instructions in the handbook, but generally let the VFD’s capacitors a                few  seconds to fully discharge.
3. Turn On electricity: Give the VFD electricity again and watch how it behaves.

4-Deal with the Root Causes:

1. Resolving Faults:  Take action to address the root cause of the issue based on the fault code and your research.
2. Connections and Wiring: Verify that all connections and wiring are tight and properly insulated.
3. Overload Problems: Verify that the pump or fan is running properly and that the load on the VFD is within its designated bounds.

  5-Test and Monitor:

1. Restart the VFD: Follow the VFD’s manual to restart the VFD after fixing the problem.
2. Track Performance: Throughout operation, keep a careful eye on the VFD and the motor that goes with it.
3. Troubleshooting: Refer to the VFD’s handbook or get expert assistance from a licensed electrician if the issue continues.

Crucial Points to Remember:

● Prioritize safety:
Safety should always come first while handling electrical equipment. Before doing any physical inspections or modifications, turn off the electricity.
● VFD handbook:
For comprehensive information on fault codes, reset techniques, and troubleshooting, see the handbook for your particular VFD.
● Professional Assistance:
Consult a certified technician for professional assistance if you are unclear about any part of troubleshooting or resetting the VFD

Read about: VFD motor overload fault

Need Help With a VFD Trip

Variable Frequency Drives often trip due to low voltage, load-side disturbances, or installation issues. Preventing downtime requires voltage stabilization, correct drive selection, and proper setup.

At R-Aletqan, we are specialized in VFD troubleshooting, installation, and system optimization.   If you’re unsure how to handle certain VFD trip problems or need support with installation and diagnostics, you can   get a free consultation from R-Aletqan’s specialists.

Conclusion