vfd with old motor

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Forum topic by Dorty posted 09-09-2011 03:39 AM 1468 views 0 times favorited 4 replies Add to Favorites Watch
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20 posts in 2480 days

09-09-2011 03:39 AM

Topic tags/keywords: question

Hello everyone this is my first post. I have searched and read almost all the early posts about phase converters. I am currently trying to get my 1940’s JD Wallace table saw running in my garage. This table is built very well and the previous owner said it is dead on accurate. I have been a little confused with VFD’s on some of the posts I have read. Are they something I can use with a motor this old or should I go with a rotary phase converter. Any help would be great. Thanks

4 replies so far

View crank49's profile


4032 posts in 2998 days

#1 posted 09-09-2011 04:09 AM

A VFD should work, but the wave form of the power coming out of a VFD might tax an older moter more than a new motor designed for VFD service. Those old motors usually had more beef to them and will probably be fine. The net result would be overheating in a fully loaded continuous operating motor. A table saw is neither fully loaded, nor continuous.

View Minorhero's profile


373 posts in 2632 days

#2 posted 09-09-2011 04:49 AM

There are quite a few people at the forum that have put VFD’s on motors of the age and older. They do not seem to have any problems. If you have any questions the folks over there can probably answer them easily in the electrical section of their forum.

View TopamaxSurvivor's profile


18290 posts in 3703 days

#3 posted 09-09-2011 04:53 AM

My guess would be a 50/50 chance of a VFD working with that old motor. The problem is the insulation and the high frequency switching the modern VFDs use to make the 3 phase. An older style VFD from about 20 years ago would be a better bet. I would suggest checking the motor with a high megger or megaohm meter. If it doesn’t read infinity, you will definitely be better off using a roto phase.

If you hook it up to a drive, it probably won’t hurt the motor. If it the VFD doesn’t start motor it is because it is seeing ground fault through the old insulation even though the motor will run fine on normal power.

-- Bob in WW ~ "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

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20 posts in 2480 days

#4 posted 09-09-2011 05:13 PM

I think I am going to go ahead and buy A VFD. Thanks for everyone’s help

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