Motor Name Plates and MCB Ratings

Is this a 3Ø motor?

yeah sorry 3 phase motor.

Actually, you did not confuse yourself but you miss out some importance data's. You have a 3 phase motor with two type of winding connection. One is the "Star" point connection and the other connection is the "Delta" Connection.

If you look carefully at the name plate again, yo can see two type of voltage in the motor name plate. One should be showing 440 V and the other showing 220V.

If I am not mistaken, for "Star" point connection, your motor amps should be 2.5-2.4 Amp and the "Delta" connection should be 5-4.8 Amp. (Or it is the other way round)

Selection of MCB and Overload protection will depend on which type of motor winding connection that you are going to used.

"If you look carefully at the name plate again, yo can see two type of voltage in the motor name plate. One should be showing 440 V and the other showing 220V."

The calculation for your motor amps is as follows

If you used 440V supply for your motor; (Should be in "Star" Connection)

Power = 1.5KW

Amp = 1500/ (440x1.732x0.85pf)

Amp = 2.3 A

If you use 240V supply: (Should be in "Delta" Connection)

Power = 1.5KW

Amp = 1500/ (240x1.732x0.85pf)

Amp = 4.2 A

simon wan; many motors used in the USA, are 9 leads, with fixed star winding, for the low voltage connection with the remaining 3 windings, 6 leads,wired in series with the fix star winding for the 480 volt use. for low voltage the 3 winding are connected star, and
wired in parallel, 2 star winding in parallel are the low voltage connection. perry

Sorry, I thought most standard motor has 3 winding and 6 leads for selection for Delta or Star point connection. Never thought to have motor with 9 leads. I have seen one of these motor before but it was a very long time ago.

I think because it's a low motor rating, it will be just a Direct On Line Motor / On off Switch so should I choose a MCB 6x the nameplate current or will a 6C/D be sufficient?

Thanks for all your answers so far :-) Excellent Forum.

Provided that you are using a thermal overload relay to provide thermal protection (highly recommended), the function of the MCB is mainly to provide the instantaneous short-circuit protection. If so, a 6A D-curve will definitely suffice if you are running in delta configuration, and will probably be ok if you are running in star mode too.

If you add up the cost of the thermal overload relay and MCB, you may well find that it is cheaper to buy a motor-protection circuit breaker instead - this combines both functions into one package that can be precisely adjusted to match the motor.