Answer Posted / roysayan01

I think pf doesnt vary wid speed. PF mainly depends on
excitation / field current. When overexcited the pf becomes
leading while it lags when underexcited in a synchronous motor.

BUT

cos(phi)=R/Z;
& z=(x^2 + R^2)^1/2
& x=2*pi*f*L
so if speed changes(n=120f/p), frequency changes &
accordingly x changes & as a result pf changes wid change in
speed.

Really am confused.wat do u think?

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