Variable Frequency Drive

A good way to find answers to simple questions is to use a search engine.

A Good way to test an IGBT in an AC VFD - Practical Machinist

Obtain an up-to-date copy of the VFD service manual, study it thoroughly, purchase the needed test equipment, then follow the step-by-step troubleshooting section.

If you do not already have a copy of the service manual and prints, contact the original equipment manufacturer.

Also; If you have not done so already, I suggest you send at least two technicians to the VFD factory troubleshooting school so that they have a good grasp on the fundamentals as well as advanced troubleshooting methods required for proper VFD maintenance and repair.

Be very careful with substituting aftermarket parts into any VFD as there are several required critical control timing aspects that aftermarket parts often do not meet that can result in severe damage to the VFD.

Simple troubleshooting with proper test equipment can reveal shorted and/or open IGBT's as well as other small scale device issues however it will not reveal any critical timing control issues.

Only testing in a factory certified test unit can effectively and accurately identify IGBT control and performance issues.