question about induction motor

[subhpoto]

How Current vary by increasing/ decreasing the number of poles of an induction motor?. in other word what is relation ship b/w number of poles and motor current.

 

[montybaber]

I know that to calculate the synchronous rpm of a motor is

rpm = 120 x f/Np

to calculate the horsepower

HP = rpm x T (torque)/5252

and to calculate the current

I = HP x 746/V x Eff x PF

so by adding some values i have roughly worked out the following

with 415v(delta) efficiency of 90% and pf of 88% and torque of 4 ft/ib

(I1) 2 poles= 5.17A
4 poles= 2.593A
6 poles= 1.729A
8 poles= 1.296A

so as you can see that the current is inversely proportional to the number of poles, remember though you are also reducing the rpm with increase in poles

in this case the current after number of poles added (I2) =

(I2) = (I1) / (No of poles/2)


but then again what do i know...it could all just be bollox lol