# really basic vfd question



## dado5 (Nov 14, 2017)

I have been looking at used older mills and of course many are 3 phase. I have been researching vfd's and they sound great.  My question is:  Can i put a VFD on any older 3 phase machine and run it with single phase 220 or are there certain ones to stay away from?  Just want to know when I am out looking at machines.
thanks.


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## Eddyde (Nov 14, 2017)

As long as the motor is 220v 3 phase you can run it on 220v single phase with a VFD. The VFD must be sized appropriately for the motor horsepower.


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## ConValSam (Nov 14, 2017)

If you are considering used VFDs, some older models will not create the third phase with single phase input; they are designed for 3 phase input.


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## CluelessNewB (Nov 14, 2017)

Generally VFD's work out well for 200-240 Volt 3 phase motors 3 horsepower and less.   You don't see many 200 Volt motors but some show up that come out of schools.  For the 200 Volt motors make sure the VFD can be programmed for the lower voltage, many can but some can't.   For example the Teco FM50 can't be programmed for the lower voltage (I wouldn't suggest an FM50 anyway, but that's another story)   The Teco N3 and CV7300 can be set for the lower voltage.  Above 3 horsepower the economics become less attractive.


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## Ulma Doctor (Nov 14, 2017)

a point of information,
VFD's are fine to use with old motors as long as you stay inside the 30 to 90 Hz envelope for constant use.
you can go below and above the frequency range given for short periods of time without major problems on most old motors
the old style windings were designed to take 60Hz here, 50hz in other countries.

you can run old motors at 60hz, like the factory intended .
your motor will not know whether a VFD is supplying power or a 3 phase wall plug


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## dado5 (Nov 17, 2017)

Ok i am going to go to an auction that has a few old mills.  they are labeled 220/440 volts. Those would be ok to use with a vvd as well?


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## Karl_T (Nov 17, 2017)

dado5 said:


> Ok i am going to go to an auction that has a few old mills.  they are labeled 220/440 volts. Those would be ok to use with a vvd as well?



No problem. Show us pics of what followed you home


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