Help with selecting Step Up Transformer

[BatmanisWatching1987]

I have a motor that will run continuous that has the following nameplate rating, see attachment for reference.
I also typed out the key information for your use too
EDrive Rating:
Voltage Configuration: 480V/3P
Power kW: 22
Max Input Current - Amp: 52
Max Output Current - Amp: 46

Motor Rating
Max Current - Amp: 38
Power -kW/HP: 22/29.5

Motor Operating Setting
Max Power - kW/HP: 20/27

Should I use the the Max Input Current of 52A.
So 1.25*52A = 65A
Convert to kW
65A*√3*480 = 54.015kW

Would I need a 75kW Transformer based on my calculation above.
Or can I use a 30kW Transformer since the nameplate says its uses only 22kW

 

[petersonra]

Should I use the the Max Input Current of 52A.
So 1.25*52A = 65A
Convert to kW
65A*√3*480 = 54.015kW

Where did this 1.25 factor come from?

 

[retirede]

Since the drive has a voltage range, the max current will be at min voltage (380).

Operating at 480 will result in (approximately) proportionately lower current.

I roughly come up with a 50KW transformer.

 

[petersonra]

Since the drive has a voltage range, the max current will be at min voltage (380).

Operating at 480 will result in (approximately) proportionately lower current.

I roughly come up with a 50KW transformer.

Unless this guy is from overseas, it's going to be operated at 480 so I would not be worrying about what the current will be at 380.

 

[BatmanisWatching1987]

Where did this 1.25 factor come from?

For continuous operation

 

[retirede]

Unless this guy is from overseas, it's going to be operated at 480 so I would not be worrying about what the current will be at 380.

He used 480 in his calculations. That’s why I said to ratio the max current on the nameplate down based on his voltage.
He was using the max current (which would only be relevant on 380) along with 480V!

 

[xptpcrewx]

Should I use the the Max Input Current of 52A.
So 1.25*52A = 65A
Convert to kW
65A*√3*480 = 54.015kW

Use the 52 amperes. As far as the 125% factor, the NEC isn't really clear about whether it should be used or not for load calculations. Maybe someone can confirm this?

Either way, a 50-kVA transformer would be adequate as there is no code rule to size a transformer based on the "calculated load". It's common sense to size the transformer for the actual load, but it is also best practice to size for future loads/expansion (if applicable). Transformers are capable of being loaded beyond their kVA rating. Table 450.3(b) would account for overloading up to 125% before primary-only or secondary overcurrent protection would operate.

 

[Jraef]

The 125% of the drive input current rating is only required for the conductor sizing feeding the VFD; 430.122.

I would size the transformer for the VFD input, because having to change it later when someone puts in a slightly larger fan will be a pain in the rear.

 

[petersonra]

I would get the next size up transformer from whatever the input current to the VFD suggests. That'll almost always give you plenty of cushion

 

[Jraef]

I would get the next size up transformer from whatever the input current to the VFD suggests. That'll almost always give you plenty of cushion

Always opt for more cushion...