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What’s the difference between variable-speed drives, variable-frequency drives and inverters?

If you’re in the market for variable-speed drives, you’ll have noticed that they’re also sometimes referred to as variable-frequency drives or inverters. So what’s the difference?

Variable-speed drives (VSDs) relate to both AC and DC drives, and a VSD connected to a DC electric motor will vary the speed and torque of the motor by controlling the voltage and current.

Variable-frequency drives (VFDs) refer to AC drives only and control voltage and input frequency.

Inverter can be a confusing term as it’s also a shortened version of power inverter, which means a device that converts a supply voltage from DC to AC (such as a phone charger connected to a car’s battery). However, in the case of electric motor speed control, an inverter refers to a VSD or VFD.

Just to further confuse matters, drives are often referred to as ‘adjustable-speed drives’, ‘adjustable-frequency drives’, ‘AC drives’ or ‘inverter drives’. But whatever you call them, variable-speed drives are a great choice for increasing productivity, improving energy efficiency and cutting costs in a huge number of applications.

As an Authorised Value Provider of ABB drives, there isn’t much our team of expert engineers don’t know about these indispensable devices, so give Paul Scott a call on 01621 868138 or email with any questions you may have.

Variable-Speed Drives, Electric Motors

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