speed of a 60 Hz 4- pole motor?
The synchronous speed of an AC motor is the frequency divided by the number of pairs of poles. A 4-pole motor has 2 pairs of poles, so its synchronous speed is 60/2 = 30 revolutions per second or 1800 revolutions per minute. If the motor is a synchronous motor, it operates at the synchronous speed. If it is an induction motor, it operates at a lower speed determined by the load and the motor design. If there is no load, an induction motor operates at nearly synchronous speed depending on the load caused by motor losses. At rated load, most induction motors operate about 2 or 3 percent below synchronous speed. Small, inefficient motors operate at lower speeds.
Does the induction motor have 4 poles (2 pole pairs) or 4 pole pairs (8 total poles). Poles occur in pairs. Synchronous speed is 3600 RPM/# of pole pairs for 60 hertz power. The armature rotates slightly slower speed, the slip is s = (ns -nr)/ns where ns is the synchronous speed and nr is the rotor speed
