Parallel feeds to 12 Lead motor

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philly

Senior Member
We have kind of a strange 12-Lead motor where the leads aren't your typical 12-Lead arrangement or markings. It appears that each phase has (4) leads with each of the 4 leads per phase marked T1, T2, T3. The datasheet shows the motor internally being wired in Delta. I'm not sure why each lead has multiple parallel leads, but I'm assuing its so that one large lead for each phase didnt have to be brought out. This is a VFD motor.

To this motor we are running a parallel set of 500MCM feeders. My question is this:

If we terminate the 4 motor leads for each phase with the two parallel 500's for each phase this will be a rather large termination point and be rather difficult to do with a split bolt etc... Are we able to take to of the motor leads for a phase and terminate them to one of the 500 phases, and take the other two leads for the motor phase and terminate them to the other 500MCM phases?

I dont know what the code says about terminating parallel feeders to this motor application, or what downsides there are for doing this.
 

Volta

Senior Member
Location
Columbus, Ohio
We have kind of a strange 12-Lead motor where the leads aren't your typical 12-Lead arrangement or markings. It appears that each phase has (4) leads with each of the 4 leads per phase marked T1, T2, T3. The datasheet shows the motor internally being wired in Delta. I'm not sure why each lead has multiple parallel leads, but I'm assuing its so that one large lead for each phase didnt have to be brought out. This is a VFD motor.

To this motor we are running a parallel set of 500MCM feeders. My question is this:

If we terminate the 4 motor leads for each phase with the two parallel 500's for each phase this will be a rather large termination point and be rather difficult to do with a split bolt etc... Are we able to take to of the motor leads for a phase and terminate them to one of the 500 phases, and take the other two leads for the motor phase and terminate them to the other 500MCM phases?

I dont know what the code says about terminating parallel feeders to this motor application, or what downsides there are for doing this.

I don't think you can. If you connected each single 500 to two of the leads, you would no longer have paralleled the 500 MCMs, and the OCP would (likely) be too large for each of the 500s.
 

philly

Senior Member
I don't think you can. If you connected each single 500 to two of the leads, you would no longer have paralleled the 500 MCMs, and the OCP would (likely) be too large for each of the 500s.

Yes but esentially each fo the 2 sets of leads would be connected to the same point internally in the motor, so they would almost be like an extension of the motor feeders?

The drive in this case I guess would be the OCPD you are referring to.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I believe you have a bit of a quandry. Using a split bolt would not be per code because most split bolts are only rated for 2 wires, not 12. I am surprised there is no terminal block designed for this application by the manufacturer.
 

Volta

Senior Member
Location
Columbus, Ohio
Yes but esentially each fo the 2 sets of leads would be connected to the same point internally in the motor, so they would almost be like an extension of the motor feeders?

The drive in this case I guess would be the OCPD you are referring to.

Yeah, I forgot that you said this was a VFD. It is possible that would take you out or the realm of the NEC and your guidance could come from NFPA 79, Electrical Standard for Electrical Machinery. Looking through the 2007 edition quickly, I don't see any reference to paralleled, or split-load-end conductors (it is a skinny book).
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
.
To this motor we are running a parallel set of 500MCM feeders. My question is this:

If we terminate the 4 motor leads for each phase with the two parallel 500's for each phase this will be a rather large termination point and be rather difficult to do with a split bolt etc... Are we able to take to of the motor leads for a phase and terminate them to one of the 500 phases, and take the other two leads for the motor phase and terminate them to the other 500MCM phases?
I dont know what the code says about terminating parallel feeders to this motor application, or what downsides there are for doing this.

We did that on a 500HP compressor once. It's been going strong for 5+ years now with no problems. I'm not sure how the code looks at it, but from a practical common sense standpoint it sure makes it a lot easier to fit the wires in the motors j-box.
 

philly

Senior Member
After checking continuity of these leads we come up with the motor windings being wired as in the attached sketch. It looks like there are two sets of Delta windings.

Does this seem correct? If so, what is the purpose of this arrangement?
 

CFL

Member
After checking continuity of these leads we come up with the motor windings being wired as in the attached sketch. It looks like there are two sets of Delta windings.

Does this seem correct? If so, what is the purpose of this arrangement?

Are you sure you don't have a wye start motor?
 

philly

Senior Member
How can you tell the windings are connected delta and not wye?

cf

An electrician took the winding measurments, however I guess your right you cant tell from these measurments weather its a wye or delta. I'm saying its delta because the datasheet shows the motor as being internally connected in delta but only referencecs a T1, T2, and T3 connection and does not reference the 12 leads. From measuring, it appears to be 2 diferent windings.

If this was supposed to be a wye-delta start or something, then wouldn't these leads be labeled differently?
 

philly

Senior Member
Does anyone know why this motor would have two sets of windings weather they were delta or wye? (In this case they appear to be delta)

This motor is on a drive and the motor is for a kiln motor capable of providing a high starting torque.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Multi-winding motors are known, for example motors wound where each winding gives a different pole count. You can also have high phase order motors where you have more than phases A, B, and C, and the phase angles are different than 120 degrees.

But I would expect any such motor to have different terminal markings for the different windings.

-Jon
 

philly

Senior Member
philly,

Give us the info on the motor and we will surf the net until the answer is found.

Attached is the datasheet that I found for this motor. This motor is for a kiln that is connected to a VFD.

Notice that the connection diagram for the motor only shows that it has a 3 lead delta connection, when indeed it has 12 wires in the field.

I also notice that the performance curves show a rated torque, and a 1Min torque value. Could this have something to do with the windings?
 

philly

Senior Member
Attached is the datasheet that I found for this motor. This motor is for a kiln that is connected to a VFD.

Notice that the connection diagram for the motor only shows that it has a 3 lead delta connection, when indeed it has 12 wires in the field.

I also notice that the performance curves show a rated torque, and a 1Min torque value. Could this have something to do with the windings?

Ooops forgot the attachment!
 

Cold Fusion

Senior Member
Location
way north
Does anyone know why this motor would have two sets of windings weather they were delta or wye? (In this case they appear to be delta)

This motor is on a drive and the motor is for a kiln motor capable of providing a high starting torque.

Looking at the data sheet, my guess is the same motor is sold as a part-winding start. 350hp on 480V is hard to start across-the-line.

cf
 

Cold Fusion

Senior Member
Location
way north
Very good point! Can you describe briefly how a part-winding motor start works?
Two contactors - one for each winding set. Essentially two 175hp motors. Energize first contactor - motor comes part way up to speed. Energize second contactor - motor accelerates two running speed. Supposedly cuts down the inrush current and voltage drop - and it should some.

I've only dealt with one in my career. If I get a choice, that will be enough

cf
 

benaround

Senior Member
Location
Arizona
How can you tell the windings are connected delta and not wye?

cf

cf, If they were 'Y' there would only be 6 connection leads, right ? The two delta's will give

you 12, that said, I think you are right that this motor is a part winding start ' or ' can be

used on a VFD as the wiring diagram shows.

philly, I would really try to find some connection 'blocks' for both 500's and all 4 leads per

phase.
 
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