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How to achieve AC electric motor speed control

Electric motors are essential for powering a huge number of industrial processes, including mixers, conveyors and fans. However, they do have one shortcoming in that they are only able to run at their rated speed.

So what happens if your application requires the motor’s running speed to vary at different times? For example, in processes where a range of items are made using the same machinery, such as food production, the required speed will fluctuate depending on what’s being made. Replacing the electric motor every time the process changes is impractical, so another solution must be found. That’s where the variable-speed drive comes in.

A variable-speed drive (often known as a variable-frequency drive, adjustable-speed drive or inverter) is a device which allows the user to control the output speed of an electric motor.

Variable-speed drives also allow motors to be started smoothly, which can help reduce belt, gear and bearing wear which occurs during across-the-line starting (the application of full line voltage).

This clever piece of equipment offers users the ability to reduce energy costs by as much as 60% and significantly increase system production efficiency. For a 90 kW motor in continuous duty, this translates to a £9,000 annual saving - meaning return on investment is possible within a year.

Sound useful? To speak with one of our expert engineers about installation, start-up and maintenance of ABB variable-speed drives, give us a call on 01621 868138 or email

Variable-Speed Drives, Electric Motors

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