# Input power help



## djabi90 (Mar 2, 2018)

Hello everyone! I was hoping I could get some help here. I would like to thank you in advance!

So, I have this situation in which the machine I am trying to hook up requires 380V Line to Line and 220V Line to Neutral. The building in which I am installing this machine only has 208V Wye.

The machine has 2 separate three-phase transformers that has an input of 208/380/480V-Wye which then outputs to 380V Wye. The transformers are 50kVa each. According to my calculations the transformers will do about 152 Amps of a combined total. 

My question is, how many amps would I need from the 208V line that will go into the input of the transformer? Will I need 152 Amps? or Will I need 277 Amps?

Thank you!


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## telsa (May 22, 2015)

You're dealing with an EIC designed motor -- meaning it's designed for 50 Hertz, too.

Usually these are best scrapped and a NEMA motor installed...

However it would appear that your's is a skid mounted assembly that has an integral set of transformers designed for North America.

If so, then it's been properly engineered... and can tolerate 60 Hertz, too.

Power is power, so it should be a snap to convert Watts to Watts.

You left off the critical detail: is this a two transformer open delta three-phase transform scheme?

Is it three transformers -- each single phase?

No answers with our heads in a bag.


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## djabi90 (Mar 2, 2018)

It is not a skid mounted transformer. However, speaking with the engineers from China they have stated that running the machine at 60 hz is not a a problem. 

The two separate transformers are Wye to Wye configured three-phase. Meaning they both have 5 wires for primary and 5 wires for secondary.


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## brian john (Mar 11, 2007)

djabi90 said:


> Hello everyone! I was hoping I could get some help here. I would like to thank you in advance!
> 
> So, I have this situation in which the machine I am trying to hook up requires 380V Line to Line and 220V Line to Neutral. The building in which I am installing this machine only has 208V Wye.
> 
> ...


You got it


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## MechanicalDVR (Dec 29, 2007)

Welcome aboard @djabi90!


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## varmit (Apr 19, 2009)

50 kva per xfmr:
208 volt
50000/(208 x 1.73) = 139 amp x 2 transformers = 278 potential FLA

380 volt
50000/9380 x 1.73) = 76 amp x 2 transformers =152 FLA secondary

The minimum circuit to power both transformers would be (1) 350 amp circuit or (2) 200 amp circuits. ( FLA x 1.25)

If you installed one feeder circuit, there would be some taps and over current devices to install where ever you split to each transformer, unless this is already provided on the machine.

Fans and pumps are where there is often a problem with 50 Hertz equipment operated on 60 Hertz. The reason being that the 50 Hz motor will run about 17 percent faster on 60 Hz, therefore the current is higher. If most of the motors are on VFDs, they will work fine.


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## frenchelectrican (Mar 15, 2007)

djabi90 said:


> It is not a skid mounted transformer. However, speaking with the engineers from China they have stated that running the machine at 60 hz is not a a problem.
> 
> The two separate transformers are Wye to Wye configured three-phase. Meaning they both have 5 wires for primary and 5 wires for secondary.


Y-Y transfomer can be little tricky to deal with it and please pay attetion to the connection when you hook it up.

Read the nameplate for tranfomer connection to make sure you got right supply voltage connection.

I have dealt quite few 380 volts motors over here in my area. However .,, double check the motor nameplate to make sure they are set up to run on 60 HZ source if not then you may have to see if they came with VSD and program the output to 50 HZ max speed unless spec'ed other wise.


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## MDShunk (Jan 7, 2007)

I've run literally hundreds of 60hz designed pump motors at up to 90hz on a VFD for years and years (they call that "electricians rescuing an engineer's poor design"), so I wouldn't bat an eye about running a 50hz motor on 60hz... unless the application is highly speed sensitive.


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