Using 220/380 V motors on 240/280 V service

[agelec]

An Asian company has shipped several 220/380 V 3 phase motors to use at a location where a new service will be installed. The only options are 240 or 480 volt. The largest motor is 75 hp. What is my best option to make things work short of sending all of the motors back?

 

[busbar]

Search this site using keywords " 50Hz 60Hz " for earlier discussion.

 

[agelec]

busbar, thanks for the suggestion which I checked out, but the nameplate on the motors is already 60 Hz, and the nameplate motor rpm is in the normal 1700 to 1750 range for 240/480 motors

 

[busbar]

Pardon my mistake, agelec. 380/220V is usually associated with 50Hz gear. With a motor of 75HP, 480V service would typically be most economical compared to 240V. A bucking autotransformer arrangement may do the job. Is the 480V available 4-wire, meaning 480Y/277V service? Can you provide the per-phase current needed by the 380V equipment?

 

[mdonner]

380/220V rated motor has 220V rated coils (Y connection for 380, Delta for 220).
If motor winding will tolerate 240V (check data sheet) then you can use it directly with the Delta connections, otherwise you will need an autotrafo (in this case go for 440V and 380 Y connection to reduce current).

 

[481977]

hi,
for your problem if your motor marked 50 hz then you can also drive it on 60 hz but it takes some cut out of load means it can not run on full capacity asd on 50 hz and vise versa.

now if your motor is 220v ,50hz then it will run on 240v,60 hz but not on full load .

 

[purplepete]

I have a sort of dumb observation.
The 240/480 volts sounds suspiciously like a single-phase centre tapped transformer service used commonly in rural Australia. Are you really getting three phases or merely a centre-tapped single-phase supply. Please accept my apologies if you are actually being offered three-phase 240 volt or three-phase 480 volts.
Cheers

 

[agelec]

Thanks to everyone for your help. We will be using the motors at 380 volts auto-tranformed down from 480 volts. This is a solid 480 volt, three phase system. The motors are listed for operation at 60 cycles 220/380 volts.

 

[induction]

If the motor has A multi circuit connection you can just have them recconected for 440 volt. Most motor from over seas have multi circuit connection. I have reconected them or rewound them for the correct voltage.

 

[Marke]

A silly question, but have you gone back to the motor manufacturers and asked them the question?
I suspect that someone forgot to mark the nameplate correctly. If you alter the frequency, you nedd to alter the voltage also. 220/380 is a standard 50Hz supply, I have never come across that on 60Hz. If the motor is, as I suspect actually would for 380V 50 Hz, then you can run it on 460V 60Hz. In fact I would expect that a motor marked 380volt 50Hz would be suitable for operation at 415 volt 50Hz which is very common. At that voltage the rated current will fall, and if this is the case, you could operate it at 480 volt 60 Hz with no problems.
Note, it will be star connected for 380 - 480 volt operation.
You could try connecting it open shaft, star connected, to 480 volts and measure the no load current. If the no load current is higher than 30 - 35%, then operate it on the lower voltage. If the no load current is less than 35%, then there will be no problem operating it continuously on 480 volt. Note however that the full load current will be much lower than the 380 volt rating.

Best regards,

Mark Empson

http://www.lmphotonics.com