When choosing a engine for an application, a primary consideration is the speed range it will be operated in. Whenever a motor is run substantially slower than its ranked base speed, several potential adverse effects will come into play, including reduced cooling performance, reduced power effectiveness and a alter in the motor’s rate and torque features. To mitigate this issue, some motors and quickness controllers have already been designed especially to drive lots at low speeds with precise control.
Most domestic and commercial motor applications use 3-phase speed reducer gearbox asynchronous induction motors, which operate at a speed that is determined by the frequency of the supply power. When an application operates at a continuous speed, the only thing that is required could be a gearbox or velocity reducer that brings the 
engine speed down to the required level. However, many applications need the acceleration of the motor to be diverse during operation.
This is normally achieved utilizing a VFD or Adjustable Frequency Drive, which controls the speed by modifying the frequency fed to the motor. Selecting the most appropriate electric motor and VFD type depends upon a variety of factors, however, it is necessary to first look at the way the characteristics of a motor change when the velocity is reduced.
A motor usually includes a base speed, specified by the product manufacturer, that it can be made to operate at. Nevertheless, if a electric motor is operated below the bottom speed, it could experience reduced performance of the coolant system. Especially with typically used Totally Enclosed Lover Cooled (TEFC) and ODP (Open Drip Evidence) motors, where the cooling system consists mainly of a shaft-mounted enthusiast, a decrease in speed results in reduced airflow over the motor and loss of cooling, and warmth buildup occurs. Especially when the electric motor is operated with full torque at low speeds, heat can easily build up in the motor to harming levels.