Rewired 25 hp motor current too high???

[IntegrityTesting]

Hi All,

I have a few other related posts here, but kept them separate for simplicity...

Basically I had a dual voltage 230/460 25hp motor that I was trying to utilize as an idler motor for a phase converter. The motor only had 3 leads led into the junction box... When I connected it to 220 single phase after running up with a pony motor, my no load idle current was 5A/leg (3A with caps between the lines and generated leg)

This led me to believe the motor was wired permanently high internally... I had a motor shop put the 9 leads on it for a painful $220...

BUT...................................

Now connected low, and connected to the 220 (measured 245) my no load idle current is 35A!!!

What gives? I expected double the 5A, or 10A/leg wired low, and could reasonably accept a little more like 12-15A... But why would my new low voltage idle current be 7-10X what it was ???

Thanks for your help!
Ed

PS: here are my other related threads
Same question worded differently:

http://www.eng-tips.com/viewthread.cfm?qid=360297

rewiring 20hp thread

http://www.eng-tips.com/viewthread.cfm?qid=360301

 

[waross]

Roll the leads to check for an unsymmetrical internal connection.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[IntegrityTesting]

Roll the leads to check for an unsymmetrical internal connection.
Bill

Thanks Bill... I assume you mean try every possible L1/L2 to A/B/C combination and check for current differences? OR... Did I miss the mark completely... (and possibly the entire target range)?

My contactor went out... another is on the way... will do... I also plan on taking current readings of individual motor leads at the same time... Maybe I can discover something there...

Finally... The motor plate shows a 2 contactor partial winding configuration for the low voltage...

Contactor 1 = 1-2-3
Contactor 2 = 7-8-9

I'm only powering a 10 hp compressor that at latest configuration is drawing 18A on the generated leg from the 25hp... The other two legs pass through of course, and draw 25ish ... I was toying with the idea of dropping one of these winding sets with another timed circuit after my inrush for the compressor load drops off... If my FLA of the 25hp idler is 67A and my load on the generated leg is 15A, what do you think about this idea??? Maybe even drop the two energized windings and leave a full winding for the generated phase??? Can I do that?

Another member here ScottyUK has calmed me down a little blood pressure wise, about the load this whole system is drawing... BUT... I think it's still ridiculous for a 10HP compressor to be drawing 60A @ 240 single phase ...

Sorry for being so wordy!

Ed

 

[LionelHutz]

A 10hp, 230V single phase motor is rated at about 60A per phase. You're running this phase converter motor and the 10hp compressor motor and drawing 60A per phase. What exactly is the problem with 60A?

You obviously did not have a 230V/460V motor if you had to get a shop to re-connect it to allow using the lower voltage.

Also, you don't add currents. 60A per phase means the motor draws 60A, not 120A.

Finally, if no-one is answering your thread that doesn't mean start a new one to ask the question again. Personally, I'm believing this is hobbiest related which is against the site rules meaning the whole mess should be red-flagged and deleted.

 

[waross]

That is a standard double wye, part winding start motor. Nine leads. If you have 12 leads, connect 10,11,and 12 together and forget them. then use the 9 lead diagram for the remaining 9 leads. This is NEMA numbers, not arbitrary numbers.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[IntegrityTesting]

A 10hp, 230V single phase motor is rated at about 60A per phase. You're running this phase converter motor and the 10hp compressor motor and drawing 60A per phase. What exactly is the problem with 60A?

You obviously did not have a 230V/460V motor if you had to get a shop to re-connect it to allow using the lower voltage.

Also, you don't add currents. 60A per phase means the motor draws 60A, not 20A. 1

Finally, if no-one is answering your thread that doesn't mean start a new one to ask the question again. Personally, I'm believing this is hobbiest related which is against the site rules meaning the whole mess should be red-flagged and deleted.

LionelHutz
I apologize if I’ve offended you or “broken the rules” here… I truly did not intend to… Yes I opened another thread to ask the question differently… I posted on a couple different websites, didn’t realize I was drafting another almost the same question, but linked them once I realized it… I truly have a problem that needs to get sorted out so I can get working again…

That said… I’m pretty sure I wouldn’t NEED a rotary converter setup if I had a single phase 10hp… I don’t… I have a 3ph/28A leg load motor… The 25hp is indeed dual voltage unless somebody stole a plate from another motor and riveted it on this one….

That is a standard double wye, part winding start motor. Nine leads. If you have 12 leads, connect 10,11,and 12 together and forget them. then use the 9 lead diagram for the remaining 9 leads. This is NEMA numbers, not arbitrary numbers.

Bill,

Super… Thanks for your help! I have no problem tying the 3, and connecting new leds for the remaining nine… What I need help with is determining which lead/tap is what number… Standard NEMA convention… How do I figure this out???

Thanks Again!
Ed

 

[LionelHutz]

OK, I will spell this out as clearly as I can - Everything you described is perfectly normal. No-one can help you fix a problem that doesn't exist.

As for the motor - A dual voltage motor has the motor leads in the terminal block to connect it for either voltage. You motor WAS NOT a dual voltage motor since you PAID a motor shop to convert it to dual voltage. The motor must have been re-wound with a different winding configuration compared to the original so what you have now is highly questionable.