240 volt motor on 120 volts?

[MichaelBikel]

I picked up a grinder second hand and didn't realize the motor is three phase and runs on 230 or 460 V. Is there anyway to get it to run on 120 without damaging it?

 

[LXCam]

Nope. You could however get a VFD and wire it to 240v single phase and have a cool set up.........for a chunk of change.

 

[MichaelBikel]

Ok...GRINDER FOR SALE...

 

[cvairwerks]

The chunk of change is going to depend on what size the motor is. 110 single phase to 230 3 phase VFD for up to 1 hp is around 230$. More hp, and you will have to move to 230 single phase. and about the same cost for up to 5 hp.

 

[Ign]

The chunk of change is going to depend on what size the motor is. 110 single phase to 230 3 phase VFD for up to 1 hp is around 230$. More hp, and you will have to move to 230 single phase. and about the same cost for up to 5 hp.

This. You can go 110V to 220 3ph for small motors. Search for Dealers Electric, Teco VFD's (as one option)

 

[Packard V8]

The chunk of change is going to depend on what size the motor is. 110 single phase to 230 3 phase VFD for up to 1 hp is around 230$. More hp, and you will have to move to 230 single phase. and about the same cost for up to 5 hp.

Last TECO I bought for 110V single phase to up to 1hp 3-phase 220V was only $160, delivered.

Worked beautifully, but the instruction manual and/or the software design is the worst I've ever read. The VFD uses basically two buttons for eleventy-zillion functions; requiring a complex press-twice-with-left-forefinger-then-other-button-three-times-and-first-button-once, to change operations. Just adding a couple more buttons would have vastly simplified the operation.

jack vines

 

[Know Wosad]

I picked up a grinder second hand and didn't realize the motor is three phase and runs on 230 or 460 V. Is there anyway to get it to run on 120 without damaging it?

What I can gather from the make and model and photo you posted is that......OH WAIT !

 

[MichaelBikel]

So apparently the variable speed box allows the 240 motor to run off 120 somehow...so I'm going to rig it up and try it out before I make a decision about selling

 

[bsaint]

So apparently the variable speed box allows the 240 motor to run off 120 somehow...so I'm going to rig it up and try it out before I make a decision about selling

What it does is it uses a transformer to go from 120 to 240. Then it rectifies the 240 to DC. Then it pulses the DC at a very high carrier frequency to imitate the output frequency setting of 25 - 320 Hz (some specialized ones go higher). The VFD we have at work runs our pump motor at 110,000 RPM.

 

[zkling]

What grinder do you have?

 

[Mark in Indiana]

Michael,
Do you have 240V in your garage?
If so, you can run your 3 PH motor on 1 PH with a motor "run" capacitor. I ran into the same problem when I won a Black & Decker #76HA,3/4HP, 8" (circa mid 1970s) pedestal grinder at an auction. When I realized that I didn't look close enough at my grinder before bidding, I checked out the motor with an OHM meter, and saw that all was fine. This grinder is the best one that I've come across, with the lighted shields, wheel guards, and tool rests. I decided to do some research on how to run a 3 PH motor with 1 PH power before trying to resell it.

Make sure that you use a RUN capacitor. A START capacitor will have a short life being used for running a motor. I came across a YouTube video on using a motor RUN capacitor to accomplish this:

I needed to find the right size RUN capacitor for my 3/4HP motor here:
http://www.electricneutron.com/electric-motor/single-phase-capacitor-sizing/

After I connected the capacitor to the motor, it ran great! In fact, the grinder is so "mechanically" smooth, it takes 5 min. & 23 sec. for the wheels to come to a complete stop.

Here's the downside and my opinions:
1. The motor will vibrate more when running. This is due to not having a "clean" 3 phase power supply to the motor. The vibration isn't that much.
2. Single phase power with the capacitor will be harder on the motor, thus a shorter life. As often as I use my grinder, it will still likely outlast me.
3. You loose up to a third of your motor horse power. This is because you have 1 motor winding being "fooled" by the capacitor. I can still make sparks just fine.
4. It takes longer for the motor to get up to full speed. Again, not all of the motor windings are getting pure voltage. It's not that long a wait.

For my uses, the up side is:
1. I have a large, vintage, heavy duty, complete, industrial pedestal grinder with all of the bells & whistles for 54$.
2. For another 15$ for the capacitor, electrical enclosure, and misc supplies, I have a grinder that I'm very happy with.

Sorry I was a little long winded. I don't have any recent grinder pictures. Below are some pictures before finishing it.