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#59211 - 11/29/05 06:17 PM single phase 230V motor and high leg question
LoneGunman Offline
Member
Registered: 10/02/05
Posts: 141
Loc: Florida
Had a service call today to find out why a large table saw was going through motors. Table saw is a large Jet saw used daily. Customer has went through two motors in two years, didnt think that was unreasonable considering Jet is not exactly high quality equpiment. They replaced the second Jet made motor with a Dayton motor yesterday. Saw worked for the day and then this morning they called us because the saw lacked power.

The motor is 230 Volt, single phase. I started the saw and the motor sounded like a 3 phase motor thats single phasing. Theres 240 volts at the receptacle that the saws plugged into. I checked the motor and it's wired correctly.

One of the employees was concerned because he checked for voltage and after seeing the voltage on the high leg he thought that was the cause of the problem. I explained to him the high leg can be used as long as its not a 110V circuit. The instruction sheet that came with the motor said that all voltages should be plus or minus 1% of each other. Has anyone heard of a high leg causing problems on a 230 volt motor?

I didnt get a chance to check the motor out further, by the way its acting Im thinking the start/run capacitor is dead.
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#59212 - 11/29/05 07:17 PM Re: single phase 230V motor and high leg question
JBD Offline
Member
Registered: 07/12/01
Posts: 599
Loc: WI, USA
High leg to neutral is only 208V, this will eventually burn up a 230V motor especially if the utility is "soft".

High leg to any other leg is 240V which is the nominal supply voltage for a 230V motor.
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#59213 - 11/29/05 07:21 PM Re: single phase 230V motor and high leg question
WFO Offline
Member
Registered: 09/03/05
Posts: 202
Loc: Cat Spring, TX
Quote:
"The instruction sheet that came with the motor said that all voltages should be plus or minus 1% of each other":

Why would there be an instruction like this on a single phase motor? Something don't wash here.....
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#59214 - 11/29/05 07:59 PM Re: single phase 230V motor and high leg question
LoneGunman Offline
Member
Registered: 10/02/05
Posts: 141
Loc: Florida
"Quote:
"The instruction sheet that came with the motor said that all voltages should be plus or minus 1% of each other":

Why would there be an instruction like this on a single phase motor? Something don't wash here.....

IP: "

As far as I know voltage differential only matters on 3 phase motors, thats why I was confused with the instruction sheet. I dont know, maybe it is the standard sheet they put in with all of their motors.
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#59215 - 11/29/05 08:02 PM Re: single phase 230V motor and high leg question
Edward Offline
Member
Registered: 12/14/02
Posts: 308
Loc: California
Having 240volts at the receptacle is fine. How about checking for voltage drop across the starter/switch if it has one.

Check for voltage at the receptacle while the motor is trying to start or while it is running.

Do the same VD check at the motor terminal.


Edward

[This message has been edited by Edward (edited 11-29-2005).]
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#59216 - 11/29/05 09:49 PM Re: single phase 230V motor and high leg question
Tesla Offline
Member
Registered: 06/16/04
Posts: 1273
Loc: Sacramento, CA
Your mention of the high leg....

Don't tell me that this motor is high leg to neutral....

This puppy should be wired single phase, hot to hot...the full 240....wild leg then means not much.

If it was wired high leg to neutral... stop that. High legs can swing wildly against neutral since they are affected by the load balance in the 120 V circuits. I wouldn't use it.
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#59217 - 11/29/05 09:52 PM Re: single phase 230V motor and high leg question
Tesla Offline
Member
Registered: 06/16/04
Posts: 1273
Loc: Sacramento, CA
And on second thought...

Why are they not using a three phase motor when three phase is available?

Very odd. Not recommended.
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#59218 - 11/29/05 11:01 PM Re: single phase 230V motor and high leg question
e57 Offline
Member
Registered: 05/27/03
Posts: 2876
Loc: S.F.,CA USA
"Has anyone heard of a high leg causing problems on a 230 volt motor?" Not unless some one wired into the control circuit for it...

"The instruction sheet that came with the motor said that all voltages should be plus or minus 1% of each other." I would assume that the windings design needs balance or it may over heat.... One side over powered, one under powered, just a guess...
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#59219 - 11/30/05 04:07 AM Re: single phase 230V motor and high leg question
LoneGunman Offline
Member
Registered: 10/02/05
Posts: 141
Loc: Florida
No the motor is not wired high leg to neutral. Good question on why they are not using a three phase motor, Ill suggest it.
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#59220 - 11/30/05 08:55 AM Re: single phase 230V motor and high leg question
gfretwell Offline


Member
Registered: 07/20/04
Posts: 9039
Loc: Estero,Fl,usa
If this is a true delta (3 transformers) it doesn't make much difference which legs you use but when this is a delta vee, with 2 transformers that wild leg can dance around a bit in relation to the other two. I hung my Dranitz on a wild leg once, set to +/- 10% and it ran out of paper overnight.

[This message has been edited by gfretwell (edited 11-30-2005).]
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