# additional Wires in 3 phase motor



## captkirk (Nov 21, 2007)

This is shooting from the hip but i think you have what they call a weg motor....start your search there..


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## John Valdes (May 17, 2007)

Check for continuity between the two wires 20 & 21. A dead short indicates a thermal switch. A resistance reading may indicate a thermal sensor.

Check both (20 &21) wires/against every power lead to make sure they have no connection to the motor windings.

Since this is a three phase motor, two leads cannot be anything but an auxiliary device of some sort.

Are the 20 and 21 number markings on the wire themselves? (factory) or are they wire numbers someone put on them?

Tony. Weg is a manufacturer not a motor type. They are the GE of South America and located in Brazil.


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## JRaef (Mar 23, 2009)

oldwirerpennine72 said:


> ...There are however 2 additional internal wires on the block numbered 20 & 21 which connect between L1 (u1) and N.( N is not connected to the star point) Does anyone know what these two wires are for.


My first guess is that this motor has an electro-mechanical brake attached to the non-drive end of it. The power for the brake is just single phase 230V and for a 415V IEC power system, Line to N = 230V. So by connecting the brake coil power to U1 (or any line phase) and an extra wire run out to it for Neutral, the brake coil is energized at the same time as the motor windings. Energizing a brake coil RELEASES the brake, it is spring driven to apply when power is CUT from the coil. If there is a brake on it, you will have to either remove the brake to use the motor, or power the brake appropriately. Since you are converting to 230V 3 phase from a VFD, you will need to run COMPLETELY SEPARATE 230V single phase wires out to the brake coil, you MUST NOT power the brake from the VFD output.

My 2nd guess (if there is no brake attached) is that it might be a motor space heater, that's why you run the N to it because it is likely a 230V motor space heater, used to keep condensation from forming in the motor when it is not running. If you are indoors in a reasonably climate controlled shop space, no need to hook it up. The one thing I'm not clear on in your description is the connection to U1. If that is connected INSIDE of the motor peckerhead, then either it is NOT a space heater, or someone had it hooked up incorrectly. Hence it being in 2nd place of possibilities.

Another common reason for extra terminals / wires in the motor connection box it for thermal SENSOR connections to supplement the Over Load Relay. But those would not typically be done to a Neutral connection, that's why I don't think that's it.

By the way, U1, V1, W1 and U2, V2, W2 are the CURRENT connection numbers. The X,Y,Z is no longer compliant to current IEC numbering standards.


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## nolabama (Oct 3, 2007)

Let me repeat what Jreaf said about that brake. YOU MUST use a SEPARATE VFD for the brake. Do not use the motor's VFD for a brake. It's really that important.


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## John Valdes (May 17, 2007)

nolabama said:


> Let me repeat what Jreaf said about that brake. YOU MUST use a SEPARATE VFD for the brake. Do not use the motor's VFD for a brake. It's really that important.


I like to use one of the VFD's outputs for the brake. Then program the output to operate the brake.

Edit: I did not read the post as close as I should and did not see that he does have an internal connection. So it must be a brake. I have never seen a space heater connected to a winding. Not saying it does not exist. But all the space heaters I have seen and used were not connected in any way to the windings.


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## nolabama (Oct 3, 2007)

John Valdes said:


> I like to use one of the VFD's outputs for the brake. Then program the output to operate the brake.
> 
> /QUOTE]
> 
> ...


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## JRaef (Mar 23, 2009)

nolabama said:


> John Valdes said:
> 
> 
> > I like to use one of the VFD's outputs for the brake. Then program the output to operate the brake.
> ...


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## nolabama (Oct 3, 2007)

Me and Jreaf are on the same page. Bridge had a brake on VFD. Brake did about $300,000 worth of damage. Do not run brake off VFD. simple enough to remember.


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## varmit (Apr 19, 2009)

John Valdes said:


> I like to use one of the VFD's outputs for the brake. Then program the output to operate the brake.
> 
> Edit: I did not read the post as close as I should and did not see that he does have an internal connection. So it must be a brake. I have never seen a space heater connected to a winding. Not saying it does not exist. But all the space heaters I have seen and used were not connected in any way to the windings.


YEARS ago A-B sold a "motor heater" that mounted in a MCC bucket and connected to two of the "T" leads on the load side of the starter. The output was current limited to avoid motor damage. I only remember using these units on a few 100 HP, and larger motors. The heating was just enough to avoid condensation when a motor had been stopped after having been running. These things would take "forever and a day" to warm a cold motor. I have an old A-B catalog that may list these. I will post something if I find it.

Well, A-B still sells this type of "heater". Look up Bulletin 1410 motor winding heater.


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## oldwirerpennine72 (Feb 7, 2013)

*Additional wires update*

Thanks to all the guys who replied. I have now traced out the wiring It would seem that the the two wires 20 and 21 are in fact a thermal switch. I made an incorrect assumption that the blue wire on 21 was a neutral. It was not. It was in fact a wire from the starter relay coil which through the T switch connects that side of the relay coil to L1.


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## John Valdes (May 17, 2007)

varmit said:


> YEARS ago A-B sold a "motor heater" that mounted in a MCC bucket and connected to two of the "T" leads on the load side of the starter. The output was current limited to avoid motor damage. I only remember using these units on a few 100 HP, and larger motors. The heating was just enough to avoid condensation when a motor had been stopped after having been running. These things would take "forever and a day" to warm a cold motor. I have an old A-B catalog that may list these. I will post something if I find it.
> 
> Well, A-B still sells this type of "heater". Look up Bulletin 1410 motor winding heater.


I have never seen a motor winding used to heat itself. Do you mean you had some sort of control that powered a winding with the HOPE it would produce a little bit of heat. Is that what you mean?


Space heaters for motors are like small electric blankets.
They are positioned ON the winding inside the motor. They are designed to come on whenever you want.
It could be connected to any controller with an output relay.

It is rare to see space heaters stock unless you order it from the factory when buying the motor.
They are usually installed by your motor shop.

But I have never ever seen a space heaters connected to a motor winding.
Only attached/tied to the windings with their own leads brought out to the pekerhead. 
Separate from the motor windings.

Here are some examples:


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## JRaef (Mar 23, 2009)

John Valdes said:


> I have never seen a motor winding used to heat itself. Do you mean you had some sort of control that powered a winding with the HOPE it would produce a little bit of heat. Is that what you mean?
> 
> 
> Space heaters for motors are like small electric blankets.
> ...


John,
A Motor Winding Heater puts DC (or more accurately, 1/2 wave AC) on one set of windings of the motor, long aftrer it comes to rest. The MWH is current controlled to it is adjusted to only allow enough current to flow to warm the motor up from the inside just enough to keep it above the dew point. It's a great way to add motor heating to motors that were not ordered with a separate heater, plus they use the existing motor circuit conductors so no separate wiring is needed. Some VFDs and Soft Starters provide this function as well.


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## Peewee0413 (Oct 18, 2012)

Sounds correct to me


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## John Valdes (May 17, 2007)

JRaef said:


> John,
> A Motor Winding Heater puts DC (or more accurately, 1/2 wave AC) on one set of windings of the motor, long aftrer it comes to rest. The MWH is current controlled to it is adjusted to only allow enough current to flow to warm the motor up from the inside just enough to keep it above the dew point. It's a great way to add motor heating to motors that were not ordered with a separate heater, plus they use the existing motor circuit conductors so no separate wiring is needed. Some VFDs and Soft Starters provide this function as well.


Thanks JRaef. I have never seen this before. 

Thinking now how many motors people have been pulled, sent to the shop, disassembled, space heaters installed, reassembled, tested and delivered back to the customer.


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