The three types that are available are Constant Torque, Variable Torque and Constant Horsepower.Ĭonstant torque loads are those types of loads where the torque requirement is independent of speed. In this case, the type of load to be driven must be defined and the motor is selected to match the load requirement. Thus, the frame size on the two speed, single winding motor can usually be smaller than on an equivalent two winding motor.Ī second item that generates a good deal of confusion in selecting two speed motors is the load classification to which these motors are to be used. This is because the same winding is used for both speeds and the slots in which the conductors are placed within the motor do not have to be nearly as large as they would have to be to accommodate two separate windings that work independently. The two speed, one winding motor is, by nature, more economical to manufacture than the two speed, two winding motor. These motors are wound for one speed but when the winding is reconnected, the number of magnetic poles within the stator is doubled and the motor speed is reduced to one-half of the original speed. Two speed, single winding motors are of the design that is called consequent pole. In this type of motor, a 2:1 relationship between the low and high speed must exist. The second type of motor is the two speed, single winding motor. Thus, a two speed motor requiring 1750 RPM and 1140 RPM would, of necessity, have to be a two winding motor. The two speed, two winding motor can be used to get virtually any combination of normal motor speeds and the two different speeds need not be related to each other by a 2:1 speed factor. When the second winding is energized, the motor takes on the speed that is determined by the second winding. One winding, when energized, gives one of the speeds. The two winding motor is made in such a manner that it is really two motors wound into one stator.

They can first be divided into two different winding types. There seems to be a lot of mystery involved in two speed motors but they are really quite simple.

Single phase motor winding diagram