Is VFD Good or Bad for Old 3 Phase Motors

[lukebarber]

I have been looking at a couple of power tools that have a 220v 3 phase motor. I was wanting to avoid having to install a rotary converter. But I have been told the VFDs that some folks use are bad for the motors and can ruin them. Can you share any insight into this? Thank you in advance.

Here's a link to one of the motors. http://www.clrwtr.com/PDF/LEESON/LEESON-Three-Phase-AC-Motors.pdf

 

[PeterK]

I worked in the industrial world for over 30 years and installed hundreds of drives. It was fairly common for older motors used with VFDs to have shorter lives. This was claimed to be due to the frequency switching causing damage to the winding insulation. It was really often caused by running the motors at reduced speed and not having enough cooling airflow causing insulation damage and bearing problems.

Virtually all motor manufacturers sell motors designed to be utilized with drives as they have larger fans, better wiring insulation and better case cooling.

For your use you will probably only run it at 60 hertz - full speed so cooling is not really an issue. There could still be insulation degradation over time but may take years to show itself.

 

[Peter_C]

I bought an industrial scuba compressor that was 3 phase. For less money than the converter I put a brand new single phase motor into the compressor, and rewired it. Another option worth investigating. 

 

[WarnerConstCo.]

They work great and won't harm anything under normal use.

Vfds are cheap now days.

Way cheaper then swapping motors, plus single phase motors pale in comparison to 3 phase motors.

 

[Huxleywood]

The simple answer is for the amount of time and duty cycle woodworking machines tend to see (especially hobbyists) you won't see any ill effects with the insulation which is the issue.  There will be more heat in the windings at 60hz using a drive than 3 phase from the wall. 

The bigger issue is when using non drive rated motors in applications where you are running them at lower frequencies (lower speeds) where the reduced fan speed may cause excess winding temps.  In actuality I have seen few ACTUAL failures reported on WWing forums even with slower speeds.

If you plan to run the motors at 60 hz (not over or under speed) I wouldn't give it a second thought.  The only 3 phase equipment I personally would not run on VFD would be ones with sensitive electronics (such as some higher end Euro machines like sliders and shapers) where leg imbalance can cause major issues in those cases I would run a Phase Perfect. 

 

[WarnerConstCo.]

Actually, the vfd outputs a cleaner 3 phase then a lot of other phase converter options. 

I am setting up a 5hp direct drive jointer with a vfd for a customer.

 

[PeterK]

What brands are people using on tools? What sources are there?
My experience is all with industrial expensive units and not affordable for power tools.
Thanks. Pete

 

[lukebarber]

I went with a VFD from Lenze. I thought price was reasonable. I'll update the post once I start using it.