Motors ???

[nicknorth]

I need help with my motor calc

1ph 120/240v & 3ph 277/480 servive (120/240 loads are transformed from the service)

115 1ph 2hp n/p rating 19.92
115 1ph 3hp intermittent duty 5 min n/p rate 28.22
230 1ph 5hp continuous duty n/p 23.23
460 3ph 30hp intermittent 15 min n/p rating 33.20
460 3ph 50hp intermittent 10 min np rating 53.9
460 3ph 50hp n/p rating 53.9

What is the total calc motor load on the service from these motors in VA??

Show your work. I need help getting these motors down.

 

[charlie b]

Re: Motors ???

How about you showing us your work first? That is the normal practice on this Forum. You tell us what you have tried, and we help you figure out what you may be doing wrong.

 

[ronaldrc]

Re: Motors ???

I suggest using a tow motor on the 30 and 50 hp.

 

[nicknorth]

Re: Motors ???

Well do you take all the motors at 125% of name plate rating? Then multiply by the applied voltage. Then add 25% of the largest motor? I'm mostly confused about if I take the motor at 125% or not.

 

[charlie b]

Re: Motors ???

You need to read through 430. It is not easy, I know. But here are a few hints:
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• <font size="2" face="Verdana, Helvetica, sans-serif">You never use the nameplate amps. There are tables that give you the current values to use.</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">You use 125% of the largest motor only, not all motors.</font>

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• <font size="2" face="Verdana, Helvetica, sans-serif">There are special tables that apply to intermittent duty motors.</font>

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[nicknorth]

Re: Motors ???

You even use the tables for aplying the demand load to the service? Can you show me this problem worked. I have work this out, but I know am not getting the right answer.