new guy on block asking question 1

[jamcool]

Am new to the forum so HELLOOOO all,have a question,what effect is any would a 208/230 volts motor have if used in a 277 volts application 60 HZ both motor and system.

 

[jraef]

If you are speaking of a 1 phase motor, it will eventually burn up. A NEMA design motor is capable of +10% voltage, 208 to 277V is +33%. The motor would saturate, overheat and damage the winding isulation, but because the load current would technically be low, the Overload Relay may not pick it up fast enough. Really bad idea.

If you are thinking this is a 3 phase issue, you have something wrong. 277V only esists as a Phase-to-Neutral 1 phase voltage on a 480V 3 phase 4 wire system. The 3 phase voltage would be 480, not 277.

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[jamcool]

Yes! its single phase ,thanks for the answer

 

[jraef]

In the world of 1 phase transformers, you will be hard pressed to find one that goes from 277 to 208 or 230, but it will be fairly easy to find one for 480 to 240. That is still a little too high for that motor if the nameplate says 208V, but if it's 230V then no problem.

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[waross]

A 480:120 transformer connected as a 600 volt autotransformer will produce 222 volts when connected to 277 volts..
A 480:120 transformer connected as a 480 volt transformer with a 120 volt buck will produce 208 volts when fed from 277 volts.
The 120 volt winding must be rated for the motor full load amps.
respectfully.

 

[powerjunx]

jamcool,

jraef is right,

"..10% voltage, 208 to 277V is +33%."

For 1 phase, it burns up the machine.

For 3 phase, 30% variation would mean a single phase condition. Thus, it really burns up the motor.

 

[jamcool]

Thanks guys for all your help,my story is this. Where I work my boss wanted me to install a 208/230 volts motor into a system that had burnt a 277volts motor and is on 277 had reminded he of the dangers of such a move but he was insistant that it be done,I guess he has his reasons, am new to the company so he started to but alot of pressure on me,the long and short of the story is,to keep the job i have installed the motor which is so hot u can fry a egg on it,it has survived 12 hours so far,.Just wanted to hear from others their opinion.I need to stop second guessing myself(3eyes)

 

[jraef]

277V motor? That's a rare bird. I've only seen that on ceiling fans, the old paddle type circulating fans used in industrial plants because they could use the same circuit as the 277V lighting. Are you sure about that motor rating? If it's anythiong other than a paddle fan it would have needed to be custom made. Why do you have 277V anyway? Just curious.

BTW, waross made a good point about using standard off-the-shelf transformers.

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[jamcool]

The motor is used in an air handler I am in the Caribbean where we use 50HZ,120volts,208 volts or 230 volts,2 110volt legs and 1 190volt leg but I work for a Hotel that generates their own power so we at the Hotel are on 60HZ 480Volts,277 volts live and neutral and 220 live and live. 3phase+neutral, we have 4 units and we generate about 1500 megawatts of power per day(thats whst the hotel uses) and spend about $300,000 US dollers per week for petrol to run the units,but it all works it self back out with average room rates being about $250 US per night.I work in the engineering department but the company that is incharge of the power plant is a company called Yancy out of somewhere in the states(sorry if not allowed to call company names on this forum)Well thats my life,thanks again for the help

 

[jraef]

So I take it then that someone only ran a 480V line and neutral conductor to this air handler, that's how you have only 277V available? This is not typical, but sometimes OEM equipment mfrs make up their own rules as a way to force users to go back to them for replacement parts. That's unfortunate for you.

Were it my system, I would invest in installing a transformer and step down to 220 or 230V, so that standard off-the-shelf motors will work forever more. Running that motor at +33% voltage is a fire waiting to happen, and a fire in an air handler can put your Hotel out of business for the time it takes to clean all the ducts and rooms it served.

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[jamcool]

I know,I know but the chief engineer wants to have his own way,its a power and money thing with him.The more locals he can buy from the more THANKS the locals tell him(read between the lines)
Others have suggested transformers in the past but with 480 rooms (each has its own blower and chill water coil,480 at breaker then 277 lines to room, one line would feed maybe 2 or 3 motors ) and as u pointed to the installers and equipment mfrs had a plan,each room has a small step-down from 277-24 volts for the stat. controller,to them its easier to buy motors from the states at only 5 or 6 at a time than to stock pile motors or even change out or add stuff.I guess thats y they are owners, managers and persons like me JUST workers.

 

[jraef]

...and later they will blame other people for the problems that they indirectly caused.

It's good to be the king.

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[jraef]

One last serious suggestion.
Can you get the motors with PTC thermistors in them? That way you could monitor actual motor temperature instead of current and get some advanced warning of impending failure. If you already have the motors, a local motor shop should be able to retrofit thermistors into them, then you just need a thermistor trip relay or a good solid state overload relay that accepts a thermistor input as well.

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