Variable Speed Motors

More Information about Variable Speed Motors

Another type of variable speed motor is the permanent magnet motor, a DC motor variant. These motors use permanent magnets in the rotor, creating a high torque and high-efficiency motor design. The speed of these motors can be controlled through methods such as adjusting the voltage or using an electronic speed control system.

Variable speed motors find applications in a wide range of equipment, from fans and pumps to industrial machinery. The ability to control the motor speed can improve the flow rate in pumps, the airflow in fans, and the operation of various other pieces of equipment. Furthermore, the energy savings achieved by using these motors can significantly reduce costs for customers.

A newer design in the world of variable speed motors integrates a variable frequency drive directly into the motor for a more compact and efficient solution. This design has the added benefit of reducing startup energy demands, as the motor can begin running at a lower speed before gradually ramping up to the required speed.

Motor Starters, Soft Starters and VFDs

Motor Starters

Motor starters safely start and stop a motor in industrial applications. They are designed with a contactor, overload and circuit protection. They are used when basic motor control is required, where torque on the motor is not a concern and speed control is not needed. The advantages of motor starters include: lower cost, allows for remote operation, allows for monitoring of motor state (with the use of auxiliary contacts) and they are safe and efficient. The disadvantages include: high inrush current that can cause fuses to blow and breakers to trip if the inrush is too high, and the starter will allow a full torque to start the motor which can cause the motor to ramp up to full speed very quickly potentially causing the motor to wear and degrade prematurely.

Soft Starters

Soft starters protect motors from inrush current by gently ramping up the motor to full speed. They provide all of the same functions as a traditional motor starter. The advantages of soft starters include: they are less expensive than a VFD when only startup control is needed, they are a smaller system than a VFD where space is a concern and they prevent unwanted torque upon startup, prolonging the life of the motor. The disadvantages include: they are more expensive than a traditional motor starter and they do not allow for full speed control. 

VFDs

A Variable Frequency Drive (VFD) allows for the slow ramp up of a motor during startup and the slowing down of the motor during shutdown. It also allows for full speed control during the entire run cycle of the motor. VFDs provide the same functions as both the traditional motor starters and soft starters. The advantages of VFDs include: full speed control (start, stop and in-between), more custom control and monitoring, energy savings due to efficient motor usage and less wear and tear on the motors. The disadvantages include: they are more expensive and larger than other motor control options and they generate heat that may require fans or AC units.