WiremanWireman · VFD overheating: troubleshooting for electricians · 2023 NEC ·
VFD overheating
Fans, dirty heatsinks, a hot enclosure or a drive working too hard.
Before you start
How much electrical experience do you have?
This sets how much detail each step shows. You can change it any time.
Showing detail
How it works
A drive loses a few percent of the power it handles as heat in its transistors and rectifier. That heat goes into a heatsink and is carried away by a fan, so the drive depends on clean airflow and a cool enough room or enclosure. Drives are rated for a maximum surrounding air temperature in the manual; above it, they must be derated. An overheat fault means the heatsink got too hot, from poor cooling or from making more heat than normal.
Every question and answer in this guide. Tap “Step by step” to walk through it.
- With the drive running, is its cooling fan turning and moving air?
- Fan not running or weakFailed cooling fan
- Fan runningTest: Inspect the heatsink and airflow pathExpect: Clean fins and filters, nothing blocking intake or exhaust, and the clearances the manual calls for.
- Clogged or dirtyDirty heatsink or filters
- Blocked or too close togetherNot enough clearance for airflow
- Clean and clearWhat’s the air temperature around the drive, or inside its enclosure, at the time of the fault?
- Above the drive’s ratingSurroundings too hot
- Within ratingTest: Check the drive’s load and carrier frequencyExpect: Output current within the drive’s rating, with the carrier frequency at or below the level the rating is based on.
- Current near or above ratingDrive working at or past its rating
- Carrier set highCarrier frequency too high for the rating
- Both normalPossible failed temperature sensor or internal problem