Help with motor wiring issue

jeittreim · Aug 27, 2020

Hey all,

Need a bit of help on this one. I have a Monarch 61 that I am getting up and running. I have it wired with a VFD, and it works. However, I believe the motor is wired for 400 volts and I need it for 240. When I pulled the motor out to clean it up and re-wire it, I can only find 3 wires going into the case instead of 6. I even reached into the case to see if any of the wires were pushed back in, but couldn't feel anything. also did not see any other cover plates on the motor where other connections might be.

How do I get this motor properly wired for 240v use? if it stays wired for 480, will this damage the motor?

Attached are pics of the motor and info plates.

Thanks for any help.

Don's Engine · Aug 27, 2020

You have two plates on that motor?

doug8cat · Aug 27, 2020

Not that I am an expert, but some thing smells funny.
As mentioned 2 plates??
Operating at 440 VAC not common.
IMHO It maybe wired only for 440 3ph.
Ohm out wires and post here
What piece of equipment did or does this motor power?
Worst case: I have seen some weird electrical things in older, or overseas equipment, lastly someone have had their mitts in there prior to you. I say this cause from what I can make out from one tag there should be 6 wires.
Post ALL the info you can, may make sense to someone with more knowledge than I.

johnoder · Aug 27, 2020

How do I get this motor properly wired for 240v use?

See black background tag and the diagram lower left on that tag

In other words

"L" wires are bringing the juice in from where ever
"T" wires are coming from inside motor

L1 goes to T1 and T7
L2 goes to T2 and T8
L3 goes to T3 and T9

T4, T5 and T6 are together but not connected to anything else

THIS OF COURSE REQUIRES YOU TO HAVE THE NINE T wires loose to do what needs to be done

Red back ground tag may entirely supersede this - three T wires available to hook line wires to, period, and 440/460/480 operation exclusively

Rob F. · Aug 27, 2020

Would a motor rewind shop add the second tag? Maybe the "McBroom Electric" tag is from a 440 only rewind, that would explain the 2 tags, and why it only has 3 wires.

You will not be able to run this on 240, transformer or a different motor are your best options.

Cal Haines · Aug 27, 2020

jeittreim said:
Hey all,

Need a bit of help on this one. I have a Monarch 61 that I am getting up and running. I have it wired with a VFD, and it works. However, I believe the motor is wired for 400 volts and I need it for 240. When I pulled the motor out to clean it up and re-wire it, I can only find 3 wires going into the case instead of 6. I even reached into the case to see if any of the wires were pushed back in, but couldn't feel anything. also did not see any other cover plates on the motor where other connections might be.

How do I get this motor properly wired for 240v use? if it stays wired for 480, will this damage the motor?

Attached are pics of the motor and info plates.

Thanks for any help.

View attachment 297827

View attachment 297828

View attachment 297826

The motor was apparently built by Howell as a dual voltage (220 or 440), 9-wire motor and rewired by Mc Broom for some reason. Note that the Mc Broom tag lists the manufacturer as Howell, so it can't be the other way around. For whatever reason, the Mc Broom rewind didn't bring out all nine wires and left the motor as 440 only. You could take it into a motor shop and see if they can bring out the other 6 leads, but that's probably not going to be cheap. Best bet is to look for a used dual-voltage 7.5 HP motor to replace it. Around here, used 3-phase, dual-voltage motors sell for about $10 per HP.

Cal
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johnoder · Aug 28, 2020

A 12 or 15 KVA Three Phase 480/240V General Purpose Dry Type Transformer can fix this situation. ACME transformer had no problem with me running the new step down they sold me as a step up. Zero issues in 17 years. It does make a little HUM

jeittreim · Sep 2, 2020

So I did take the motor to a couple of different armature shops here in San Antonio, The consensus was that it was infact rewound for 440 only a long time ago. Every shop here gave me the same answer that they would only do a complete rewind to bring out all 6 leads and make it dual voltage again. the going rate is averaging in the $1000 to $1200 range.

My other alternative (since all my searching has resulted in 0 results in finding a replacement motor) is to purchase a 10hp new motor with a 215T frame (closest I can get to a size match for the current motor) and make an mount adapter for it as well as a new 4 belt pulley. This would run me around 700 - 800 to do. Anyone here have any luck with doing something like this? or is it worth the extra to have the current motor rebuilt?

Cal Haines · Sep 4, 2020

jeittreim said:
So I did take the motor to a couple of different armature shops here in San Antonio, The consensus was that it was infact rewound for 440 only a long time ago. Every shop here gave me the same answer that they would only do a complete rewind to bring out all 6 leads and make it dual voltage again. the going rate is averaging in the $1000 to $1200 range.

My other alternative (since all my searching has resulted in 0 results in finding a replacement motor) is to purchase a 10hp new motor with a 215T frame (closest I can get to a size match for the current motor) and make an mount adapter for it as well as a new 4 belt pulley. This would run me around 700 - 800 to do. Anyone here have any luck with doing something like this? or is it worth the extra to have the current motor rebuilt?

One of our late members, Leo Williams, owned a manufacturing company in Iowa and had 3 or 4 10EEs. He converted one using a Beel DC drive and another using an AC motor and VFD. He estimated that the cost of a VFD conversion was "anywhere from $3k to 10k depending on how much you do yourself" (link). I seriously doubt if you'll be able to do a VFD conversion for under $1200.

Cal
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Cal Haines · Sep 5, 2020

Have you ever actually done a VFD conversion on a Monarch 10EE? If so, how many hours did it take you and what additional costs did you have?

Cal
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Cal Haines · Sep 6, 2020

My mistake. For some reason I thought we were discussing the 10EE with the 440-only motor/generator. :dunce:

Cal
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