Coils

[jenkinscody]

I am doing part sizing and selection for a circuit of mine. Was curious to how much current if any a motor starter coil will pull. It controls 480V 3 phase squirrel cage but is 120v controlled

 

[itsmoked]

Can't answer that with the little info you've provided. The bigger the motor the bigger the starter. The bigger the starter the more current it draws. And yes, they all draw current.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jenkinscody]

1/2hp motor. I am trying to size my transformer.

 

[itsmoked]

Have you got the make/model number of the starter?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jenkinscody]

WEG TEFC(IP55)

my fault - 3HP motor

full load current 3.9A
Loacked rotor 30.8A
No load - 1.75A

All based on 480V numbers

 

[Skogsgurra]

Remember to take inrush current into account.
Those little control transformers have a rather bad "voltage regulation".
That means that voltage drops a lot when loaded with unexpectedly high current. The contactor coil usually does just that. So it starts closing the contacts, coil voltage drops and contacxts start opening. Not good.
Make the transformer at least five times nominal coil power. Ten times is even better.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Go with a 50 or 75VA transformer. Don't forget your motor needs electrical overload protection. And your control transformer needs 460V fuse protection.

You can buy packaged "Motor starters". You should consider it.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I was going to suggest 50 VA. Pretty common for small starters. You can usually find the coil current listed in the catalog.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[erickench]

The namplate current is used to size the overload protection. You would have to use NEC Table 430.250 to determine the actual full load current. This value according to the information that you have given for a 3 phase 3 HP 480 volt motor is 4.8 Amps.
Starters have a horsepower rating which would have to correspond with the motor hp. You must find a starter that matches the horse power rating for your motor otherwise use the FLC values as determined from the NEC.

Eric Kench, P.E.