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A variable-frequency drive is a device used in a drive system comprising the following three principal subsystems: primary drive control assembly, AC motor, and drive /operator interface.
The AC electric motor is generally three-phase induction motor. Some kinds of single-phase motors may be used, but three-phase motors are often chosen. Numerous kinds of synchronous motors offer advantages in some scenarios, but three-phase induction motors are acceptable for most functions and are usually the most economic motor selection. Motors which are designed for fixed-speed process tend to be used. Raised-voltage stresses inflicted on induction motors which are provided by VFDs demand that such motors be designed for certain-purpose inverter-fed responsibility in accordance with such necessities as Part
Voltage source inverter (VSI) drives (see 'Common topologies' subsection below) are definitely the most common kind of drives. Most drives are ACAC drives in they convert AC line input signal to AC inverter output signal. Nevertheless, in some programs for example common DC bus or solar programs, drives are configured as dc ac drives. In a VSI drive, the DC link is made up of capacitor which supplies a powerful input signal to the inverter and smooths out the DC output ripple of the converter. The drive control may also be configured as a phase converter -phase converter input signal and three-phase inverter output.
Dramatic increases have been used by control improvements in current ratings and the voltage and changing frequency of solid state power apparatus in the last six decades.