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Motorwinder said:
It is a lost art. I can't find anyone willing to learn the trade.
Man, I wish I lived closer, I'd come to work for free. I'll be picking your brain, if you don't mind...
 

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Discussion Starter #22
Damn, well now I'm all gun-shy about asking the question I was gonna ask... :jester:

Seriously though: If a pole winding fails on a generator, I know there's a way to skip that pole in the series and still keep the generator operational, but I haven't had to do it (yet).

How is that done? I'm 98.6% sure it's more complicated than simply installing a jumper. Any thoughts?

(And in fairness, there's so much to "electrical work" that it's possible for a guy to know almost nothing about motors and still be a bang-up electrician. Just depends on the focus of their career.)

-John
A generator usually has 4 rotor coils, so you couldn't bypass one of those.

If your talking about cutting out a coil in the three phase stator windings, then yes, you can cut up to 10% out of each phase. You cut the connection on the bad coil, and series jumper the coils next to it. depending which coil in the group it is. You then have to open circuit the bad coil (cut the coil) to prevent any eddie currents.

Don't be gun shy, I'm just a blue collar motorwinder not an engie.:)
 

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Back when I was a youngin (1974) I was hired at Bethlehan Steel in Johnstown Pa,Worked in elec. repair shop. We rebuilt motors generators crane controls,motor control panels. It was a big shop 42-45 guys N girls.We worked on everything from fractional hp. to large GE 6000 hp.I worked as an app. untill 1978 when they closed down.I wish i would have been able to stay in that trade.
 

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:jester: Just curious, why does that book open right to left?? :laughing:
Reason being is that it opens up to 4 pages across. Check it out here-

http://www.amazon.com/Electric-Motor-Repair-Robert-Rosenberg/dp/0030790905

One side is illistrations (two fold outs), the other is text (the other two sides folded out), telling you what you should be seeing, or how to accomplish your objectives.

Only repair manual that I've ever seen like it, simplifies the complexed.
 

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Welcome Motorwinder.

Ok here is a question for you.
Since the US now stamps the motors with the SFA,, about how much life will we be shaving off the life of a motor if we run it at the service factor amperage?

This motor pulls the same constant load 24/7. I know the motor is under sized and should be replaced. But here we have people who install what shows up when them order the wrong parts.

And here we rewound our own motors up until about 25 years ago. Now if it's 25HP or greater it goes out. But we have a hard time finding a quality shop.

Were are you.
 

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Discussion Starter #27
Welcome Motorwinder.

Ok here is a question for you.
Since the US now stamps the motors with the SFA,, about how much life will we be shaving off the life of a motor if we run it at the service factor amperage?

This motor pulls the same constant load 24/7. I know the motor is under sized and should be replaced. But here we have people who install what shows up when them order the wrong parts.

And here we rewound our own motors up until about 25 years ago. Now if it's 25HP or greater it goes out. But we have a hard time finding a quality shop.

Were are you.
It's more of a temperature thing that shortens the life of a motor. If an insulation is rated for class F (180C) and you stay under that temp, you'll get long life. If it's running hot to the touch you might want to get a pyrometer and check it. My experience is if it gets over about 170F on the outside skin, it will be much hotter on the insulation, and shorten the life.

As long as your under SF you should be ok.

Running a motor 24/7 will last longer then stop and starting.

I'm in Arizona.

Check with easa.com to find a quality shop in your area.
 

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Discussion Starter #28
Back when I was a youngin (1974) I was hired at Bethlehan Steel in Johnstown Pa,Worked in elec. repair shop. We rebuilt motors generators crane controls,motor control panels. It was a big shop 42-45 guys N girls.We worked on everything from fractional hp. to large GE 6000 hp.I worked as an app. untill 1978 when they closed down.I wish i would have been able to stay in that trade.
It's a good trade. In the 38 years I've been in it, I've been laid off a total of 2 months.
 

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Motorwinder said:
It's more of a temperature thing that shortens the life of a motor. If an insulation is rated for class F (180C) and you stay under that temp, you'll get long life. If it's running hot to the touch you might want to get a pyrometer and check it. My experience is if it gets over about 170F on the outside skin, it will be much hotter on the insulation, and shorten the life.

As long as your under SF you should be ok.

Running a motor 24/7 will last longer then stop and starting.

I'm in Arizona.

Check with easa.com to find a quality shop in your area.
Well we all know about heat, starting and running below the SF. A 225F surface temp is a sure sign of a motor running to hard.

My question was, How much life do you loose if you always run at the SF.
 

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Discussion Starter #30
Well we all know about heat, starting and running below the SF. A 225F surface temp is a sure sign of a motor running to hard.

My question was, How much life do you loose if you always run at the SF.
Can't answer that, sry.
 

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Well we all know about heat, starting and running below the SF. A 225F surface temp is a sure sign of a motor running to hard.

My question was, How much life do you loose if you always run at the SF.

This is a silly question. in order to answer this you would need a comparitive.

How much life will you lose running a motor at it's service factor as compare to running it at _____________________?

And even then it's a silly question:whistling2:
 

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mcclary's electrical said:
This is a silly question. in order to answer this you would need a comparitive.

How much life will you lose running a motor at it's service factor as compare to running it at _____________________?

And even then it's a silly question:whistling2:
Compared to running at it's full rated load.

I know it's a silly question. But some of my coworkers believe the SFA rating is what a motor should be allowed to run at.
 

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Compared to running at it's full rated load.

I know it's a silly question. But some of my coworkers believe the SFA rating is what a motor should be allowed to run at.


I know it's probably crude, but I think it's percentages. If the SFA is 10% higher than the FLA, then it would probably shorten the life by 10%.

But that's just a guess.


And I agree with you, the motor should only run in the service factor for short periods of time.
 

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mcclary's electrical said:
I know it's probably crude, but I think it's percentages. If the SFA is 10% higher than the FLA, then it would probably shorten the life by 10%.

But that's just a guess.

And I agree with you, the motor should only run in the service factor for short periods of time.
I agree with you about running at SF. Only for short durations.
Heck the same people here believe that overloading a motor & setting auto reset on the O/L's is the way to do it.
It gets them out the door with the job complete.
 

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Welcome to the forum....

I am actually working in a motor shop as well....just starting to learn the art of winding. My boss was winding motors with his father since he was 14, his father was a Coyne electrical school graduate, then my boss followed in his footsteps and also attended Coyne.

Our motor work is slow right now but the contracting side is booming right now. Within the last few months we have only wound 4 motors, but repaired about 45.
 

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Welcome to the forum....
Our motor work is slow right now but the contracting side is booming right now. Within the last few months we have only wound 4 motors, but repaired about 45.
Till America gets back on it's feet, expect to see a lot more service work for a while. Nothing new in Dodge, but we can make the old one last forever!
 

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Welcome to the Forum.

I wonder if you would know.....

If you took a 400Hz generator that is sizable, could you re-tap it to make it 60hz?

I was thinking that perhaps doubling the windings (or even tripling) could lower the frequency while giving close to the same rated output.
Now I realize that 60 does not evenly go into 400.
 
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