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What's the difference between variable-speed drives and soft starters?

As a supplier of both variable-speed drives and soft starters, we’re often asked what the difference is between the two. Without further ado, let’s answer this common question.

Soft starter

A soft starter is a device that allows an electric motor to start with reduced voltage, meaning a smooth, gradual run-up to full speed. This avoids sudden, rapid acceleration which causes huge inrush currents and exerts potentially damaging mechanical stress on the motor.

Variable-speed drive

A variable-speed drive, on the other hand, is a larger device that allows the motor’s speed to be controlled throughout its operation, as well as during start-up. This is achieved by varying motor input frequency and voltage – specified by the user via a control panel keypad.

Although soft starters are smaller and less expensive than VSDs, drives provide precise speed control and provide energy savings of up to 50%. Both devices offer motor protection, but if your application requires motor speed to change on demand, then a variable-speed drive is essential.

Gibbons supply and service ABB drives for a huge range of industrial and commercial applications, including pumps, fans and conveyors. For more information, contact our Drives Manager Alan Roberts on 07966 468430 or email

Variable-Speed Drives

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