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#165257 - 06/24/07 01:55 AM Wye/delta fire pump motor question
poorboy Offline
Member

Registered: 06/02/05
Posts: 128
Loc: Central Maine
Have a 150 HP 480 Volt 3 Phase fire pump fed from a controller with a Wye/delta starter. I am running 6 conductors and ground to the(12 lead) motor. My co worker has already hooked previous ones up and installed all 6 conductors based on the FLA on the motor name tag. Tha would be wire rated for 173 Amps, and I found in 430-22 (I think---not near my code book right now) a reference to using wire rated at 58% of FLA from the controller to the motor. This would allow the use of #2 THHN instead of 2/0 or 3/0 and be easier.

In the run configuration of the starter does it use all 6 leads at a time rather than 3 for start and the other 3 for run...it must if code allows this. Where is a good place to look for an elementary explanation of these starters?

I will be able to ask a technical rep on Monday, but I am curious now...Thanks


Edited by poorboy (06/24/07 01:56 AM)

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#165265 - 06/24/07 09:55 AM Re: Wye/delta fire pump motor question [Re: poorboy]
JValdes Offline
Member

Registered: 06/03/07
Posts: 308
Loc: South Carolina
poorboy,
Nema rates a 150 hp motor at 180 amperes at 480 3 phase. (180 amps x 1.75 = 315 amps). Use the FLA that is on your motor nameplate.
The fuses or breaker will be 300 amp. Now figure your wire size for this current. Not the nameplate FLA. Size your overload for the motor nameplate FLA.

The motor uses all six leads for wye and delta, with the wye having leads 4,5,and 6 tied together momentarily. Connect all three contactors as shown on your diagram. "trust me, you may not get it right the first time you try to run it"......lol

Since this is a fire pump it may not be considered continuous duty. That will change your values.


Edited by JValdes (06/24/07 10:04 AM)

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#165289 - 06/25/07 04:28 AM Re: Wye/delta fire pump motor question [Re: JValdes]
poorboy Offline
Member

Registered: 06/02/05
Posts: 128
Loc: Central Maine
Thank you for your reply! It's not that I can't get a rep to tell me what to install. but I sure like to understand what I'm doing. Your comment about the 4,5,6 leads tied together momentarily is along the ideas of what i was thinking, and I will continue to investigate. The reason for the reduced size of the 6 wires from controller to motor, then, is that each is only one run of two in a set of parallel runs? I will have one set of 3 wires from service to fire pump equip's line side fully rated for the FLA plus percentage required, and then two sets of wires from controller to motor rated at 58% of whatever value the duty requires giving the starter the ability to momentarily run as a wye config and then run as a delta with parallel runs.

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#165292 - 06/25/07 06:10 AM Re: Wye/delta fire pump motor question [Re: poorboy]
gibbonsseabee80 Offline
Member

Registered: 10/10/05
Posts: 40
Loc: Chesapeake, VA
I just hooked up a 20hp Armstrong (Emerson motor) fire pump in a building. It was 200volt Low/400 high . It had 12 leads coming out of the peckerneck on the motor. 1-12. It had two options for the low configuration and two options for the high. You could wire it Y start (low config.) or Delta run (low config.). And the same choice for the high connections. This motor was a direct change out in our existing building. It had two interlocks for emergency gen. power and Normal power. Our building is 120/208 three phase. We wired it in a Y start. I just looked at the wiring diagram on the motor. It will only lets you wire it in one configuration only in low or high with all 12 motor leads. Your motor and controller might be different. Maybe your friend paralelled the conductors from the controller to the motor three phase (6six conductors 480 volts) I have not heard of your scenario before. I think the twelve lead motor gives you different options for different system voltages. Here is a interesting forum below related to your question. I was a little confused by your forum question.

http://www.eng-tips.com/viewthread.cfm?qid=127598&page=60
_________________________
Brian Gibbons

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#165297 - 06/25/07 07:39 AM Re: Wye/delta fire pump motor question [Re: gibbonsseabee80]
gibbonsseabee80 Offline
Member

Registered: 10/10/05
Posts: 40
Loc: Chesapeake, VA
Ok,
I just got some more information from the posting "12 lead motors". I should have looked at the other posting before posting a reply. So I am learning about the Wye/Delta starter. Our existing system did not have that. But this is very interesting.
_________________________
Brian Gibbons

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#165303 - 06/25/07 08:34 AM Re: Wye/delta fire pump motor question [Re: gibbonsseabee80]
JValdes Offline
Member

Registered: 06/03/07
Posts: 308
Loc: South Carolina
Lets not complicate this issue. Can you get an electrical engineering pocket hand book?
Motor shops always pass them out to their customers. Maybe "Ugly"s" has the diagrams.
All you need to do is see the connections and the legend. Then this becomes very clear.
Wye/delta starting has been around forever. Whether it is 12 lead or 6 lead.

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#165304 - 06/25/07 08:47 AM Re: Wye/delta fire pump motor question [Re: JValdes]
gibbonsseabee80 Offline
Member

Registered: 10/10/05
Posts: 40
Loc: Chesapeake, VA
JValdes,
I agree with you. I was just trying to understand his question. Ugly's unfortunately only has 9 lead diagrams, not twelve.
_________________________
Brian Gibbons

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#165321 - 06/25/07 02:11 PM Re: Wye/delta fire pump motor question [Re: gibbonsseabee80]
poorboy Offline
Member

Registered: 06/02/05
Posts: 128
Loc: Central Maine
I have been an electrician for 30 years. Much of the time I have worked on commercial jobs---schools, office bldgs, hospitals---and also have been involved with small sawmills and the like. The latter is the extent of my industrial experience until 3 years ago when my company took on the maintenance of a company which has concrete and asphalt batch plants and large rock crushing operations.

That means that all my career I have seen electric 3 phase motors with 3 wires running to them. What few motors were large enough to need soft start starters were reduced voltage type, meaning they also had 3 wires feeding the "peckerhead".

The company who has the rock crushers has a few big motors with soft starts---all reduced voltage except one which I now know is prob. wye start/delta run (or possibly part winding start??) because it has 6 leads leaving the starter.

For that reason when I was told we were running 6-3/0's to this fire pump when we had just run 3-250 MCM to feed it's controller I asked why it was 6 wires and why so big. It was my first experience ever running more than 3 wires to the motor and thus made me curious.

It is very clear now that this allows the motor to be fed one way for start up (by the 3 contactors in the controller swapping leads around---temporarily re-wiring the peckerhead if you will) and another way for run (by the 3 contactors swapping the 6 wires around to being 3 sets of parallel runs to carry the 180 amps FLA of the 150 HP motor).

We ran 6-#1 Copper THHN's to the motor today, and I have a clear mind about it because I now know that 3 of the "half size" wires (#1) will be adequate to carry the less than FLA start up current while it is "wye", and that parallel runs of #1 will carry the 180 Amp load when it is on "run" and in the delta configuration.

You're never too old to learn in this trade.

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#165328 - 06/25/07 03:29 PM Re: Wye/delta fire pump motor question [Re: poorboy]
gibbonsseabee80 Offline
Member

Registered: 10/10/05
Posts: 40
Loc: Chesapeake, VA
Poorboy, I Like your last line of your last reply. I love these forums because you always learn something new on here. I called another old timer about the wye/delta starter today. He worked on one 18 years ago at a commercial ice making factory in New York. He said they were very common before newer technology. I got the whole rundown also between him and here. Great post.
_________________________
Brian Gibbons

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#165335 - 06/25/07 06:55 PM Re: Wye/delta fire pump motor question [Re: poorboy]
winnie Offline
Member

Registered: 09/15/03
Posts: 652
Loc: boston, ma
 Originally Posted By: poorboy
We ran 6-#1 Copper THHN's to the motor today, and I have a clear mind about it because I now know that 3 of the "half size" wires (#1) will be adequate to carry the less than FLA start up current while it is "wye", and that parallel runs of #1 will carry the 180 Amp load when it is on "run" and in the delta configuration.


A small clarification: None of the 6 leads are actually electrically in parallel, meaning connected at both ends to form a single conductor. Instead each lead is connected to a separate coil terminal. In a standard delta connected motor with three leads coming out, each lead is connected to a _pair_ of coil ends (well really sets of coils, each comprising one phase), and each lead carries the vector sum of the current from the two coils. Since the two coils are out of phase, the net current from the pair is 1.732 times the current of either one.

Said differently, you might have 10A flowing though a coil set from phase A to phase B, 10A flowing from phase A to phase C, but 17.32A flowing in the phase A lead to the motor.

But in a wye start/delta run motor, each wire gets directly connected to one coil, and the currents get joined in the contactor. Each conductor has to carry the full current of the respective coil. In the example above, each conductor has to carry the full 10A, not half of 17.32A. This is why you have the factor of 0.58, rather than a factor of 0.5, and also why you can 'parallel' conductors smaller than 1/0 in this case. (1/1.732= 0.577)

-Jon

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