This section is the controlling unit responsible for controlling the switching operation, output frequency, output power. Related Post: What is DC Drive? Working and Types of DC Drives.For a visual representation, the input and output waveforms are given with the circuit. The rectifier converts the sinusoidal input into a pulsating DC that swings between the maximum positive peak and zero volts. Three of the six diodes are connected in forward bias with the positive DC output while the remaining three diodes are connected in reverse bias with the negative DC output. It consists of 6 diodes where each phase is connected with a pair of diodes for rectification. The given circuit represents a three-phase diode rectifier. Whereas the diode rectifier is used for uncontrolled conversion while the thyristor offers controlled switching that varies the output DC power. Six diodes are used for three-phase power conversion while 4 diodes in bridge configuration are used for single-phase AC power conversion. It is made of 6 or 4 diodes or thyristors. It is a full-wave rectifier that converts the AC power into unfiltered DC. The input AC supply is connected to the Rectifier section of the VFD. Related Post: What is AC Drive? Working, Types of Electrical Drives & VFD.
Each one of the circuits is explained below. These sections are Rectifier Section, DC Bus / Filter Section, Inverter Section and Control Unit Section. Simply put it converts the AC into DC and then into AC having adjustable frequency but the operation uses four blocks or sections of VFD. The main function of a VFD is to vary the operating frequency of an AC supply. The block diagram of a VFD is also given below.Įach block is explained in detail down below. The four blocks or sections of a VFD are Rectifier, DC bus/filter, Inverter and Control Unit. Generally, a VFD is made of four blocks or sections where each section has its own function.
It even enables a motor to run above its rated speed by increasing the frequency. Since the speed of an induction motor depends on the supply frequency, the VFD can be used to vary its speed.Ī VFD is a power converter that uses electronic circuits to convert a fixed frequency and fixed voltage into a variable frequency and variable voltage.
As its name suggests it is an adjustable frequency drive that varies the frequency of the AC supply.
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