Turndown ratio in AC motor speed control
When choosing a electric motor for a credit card applicatoin, a primary consideration may be the speed range it will be operated in. When a motor is run substantially slower than its rated base speed, numerous potential adverse effects may come into perform, including reduced cooling performance, reduced power performance and a modify in the motor’s rate and torque features. To mitigate this problem, some motors and swiftness controllers have been designed especially to operate a vehicle a load at low speeds with precise control.
Most domestic and commercial motor applications use 3-phase asynchronous induction motors, which operate at a speed that’s dependant on the frequency of the supply power. When an application operates at a constant speed, the only thing that is required may be a speed reducer gearbox gearbox or quickness reducer that brings the electric motor speed down to the mandatory level. Nevertheless, many applications require the swiftness of the motor to be varied during operation.
This is usually achieved using a VFD or Adjustable Frequency Drive, 
which controls the speed by modifying the frequency fed to the motor. Choosing the right electric motor and VFD type depends on a variety of factors, however, it is necessary to 1st look at how the characteristics of a motor change when the rate is reduced.
A motor usually includes a base speed, specified by the manufacturer, that it is certainly made to operate at. However, if a electric motor is managed below the base speed, it could experience reduced efficiency of the coolant system. Especially with typically used Totally Enclosed Lover Cooled (TEFC) and ODP (Open Drip Proof) motors, where the cooling system consists primarily of a shaft-mounted lover, a decrease in speed results in decreased airflow over the electric motor and lack of cooling, and high temperature buildup occurs. Especially when the motor is operated with complete torque at low speeds, heat can easily build up in the motor to damaging levels.