Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

speed range
the minimum and maximum speeds at which a motor must operate under constant or variable torque load conditions.

A 4:1 speed range for a motor with a top speed of 1800 rpm means that the motor must be able to operate as low as 450 rpm and still remain within regulation specifications. The controllable speed range of a motor is limited by the ability to deliver required torque below base speed without additional cooling.