A 16 pole synchronous motor runs at a speed of 450rev/min Determine:A) The supply frequencyB) The speed at which it would run if it operated at a frequency of 55Hz
both of the two people above are correct in their formula, one uses 120f/no. of poles, the other uses (60)f/pole pairs which are equal, besides poles are always pair in either motor or generator windings.
A) The frequency times 60 = rpm times number of pole pairs. therefore the frequency = (450 X 8)/60 = 60hz Note pole pairs used not poles and frequency is times 60 to convert to revs per second B) (55 X 60)/8 = rpm 412.5
on ac motors in general the sync speed is equal to the 120 x frequency divided by # of poles RPMsync = 120 x frequency / #poles 450 = 120 x frequency / 16 frequency = 60 @ 55 hz the speed would be 412.5 there is no factor for slip ratio in a synchronous motor, it runs at sync speed, the only thing will be the ammount of rotor lag behind the stator as a function of torque until reaching motor limits, beyond which it will break synchronization and cause possible damage to the motor.
