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Understanding the Technology Behind Variable Speed Drives

August 03, 2023

Industries across the globe are constantly seeking innovative solutions to optimize their operations. Efficient control over the speed of a motor is required everywhere from manufacturing processes to HVAC systems. That is where variable speed drives (VSDs) come into play. Variable speed drives bring flexibility and energy savings to numerous applications. By facilitating precise control over motor speed, VSDs have become an indispensable tool across a wide range of applications. Varying motor speed through frequency adjustment is a fundamental principle behind variable speed drives. Let us explore various components of a VSD.



Important components in a variable speed drive



Input rectifier or converter:

An input rectifier or converter is responsible for converting the AC power supply to CS power. This conversion process involves changing the waveform of the voltage. The change happens from sinusoidal to pulsating DC through diodes. These components also help maintain performance efficiency and reliability through the VSD system by promoting a consistent and stable supply of electricity.


DC Link:

In simple terms, the DC link is the bridge between the input rectifier and the inverter. The primary objective of the DC link is to ensure smooth power flow to the electric motor. It houses capacitors that store electrical energy converted from AC to DC by the rectifier. This stored energy is then used by the inverter to produce variable frequency AC power that dictates the speed of the motor. The DC link helps maintain the stability in voltage and current supply, thus, ensuring consistent performance of the motor.



AC power is required to control the speed of the motor. The inverter converts DC power from the DC link to AC power, which is then used for the aforementioned process. The alternating current waveform is generated by multiple power electronic switches that rapidly switch on and off. These switches are typically made of transistors or insulated gate bipolar transistors (IGBTs), with high switching speeds and the capacity to handle high voltages and currents.


If you are looking to enhance your operations' performance while saving costs and reducing environmental impact – consider integrating variable speed drives from Bauer GMC into your systems! We also supply high-quality Danfoss VFDs.