MD Series Multi-Speed Motors

Multi-Speed Motors

Some motors are designed to operate at two, three, or four separate designated speeds. The speed of an induction motor depends on the number of poles built into the motor and the frequency of the electrical power supply. Multi-speed motors are available up to 500 hp, and are very reliable, but have several drawbacks.

The stator slots have to be bigger than those of single-speed motors in order to accommodate two or more sets of windings. As a result, the motors are bulkier and cannot be easily retrofitted. The current-carrying capacity of the copper is poorly utilized since only one set of windings is active at a time. Because of their dual speed design, however, they still have lower operating efficiencies than comparably sized single speed motors.

Multiple speed motor starters typically cost up to twice as much as single-speed motor starters. Multi-speed motors themselves cost 50-100 percent more than single-speed motors. Two-speed motors can be used to save energy in such applications as air volume control in facilities that have large differences in day-to-night or weekday-to-weekend air flow requirements. A dual speed fan rated for 1,200 and 1,800 rpm, for instance, can reduce fan energy requirements at night and on weekends by 70 percent.

Brands: ABM

General Technical Data

  • Rated Power

    0.12kW to 315kW

  • Standard



ABM offers a standard range of two-speed three phase motors:

Two-speed three phase motors with a single winding – pole changing windings

It is applicable for electric motors with poles ratio 2:1.

1500/3000 rpm, 2p= 4/2

750/1500 rpm, 2p=8/4

500/1000 rpm, 2p=12/6

These motors are produced with a single winding according to DAHLANDER scheme. Can be offered in two different executions depending on the application and requirements:

Winding according to DAHLANDER can be designed for switching ∆/YY or Y/YY. This assures different powers and starting torque ratios at the two different rotation speeds. It is used for various applications.

In case of any additional information needed, don’t hesitate to contact us.

Two-speed three phase motors with two separate windings

It is used in electric motors with ratio between the poles respectively rotation speeds different than 1:2.

1000/1500 rpm, 2p=6/4

750/1000 rpm, 2p=8/6

750/3000 rpm, 2p=8/2

ABM (44)