jenkinscody
Electrical
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
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Coils
- Thread starter jenkinscody
- Start date
- Status
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 -
Keith Cress
kcress -
- Thread starter
- #3
jenkinscody
Electrical
1/2hp motor. I am trying to size my transformer.
Have you got the make/model number of the starter?
Keith Cress
kcress -
Keith Cress
kcress -
- Thread starter
- #5
jenkinscody
Electrical
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
my fault - 3HP motor
full load current 3.9A
Loacked rotor 30.8A
No load - 1.75A
All based on 480V numbers
Skogsgurra
Electrical
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
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
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
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
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 -
You can buy packaged "Motor starters". You should consider it.
Keith Cress
kcress -
- Moderator
- #8
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.
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.
- Status