PLCs are used to automate the control of VFDs in industrial applications. Integrating VFDs with PLCs brings significant advantages in terms of energy efficiency, process control, and operational flexibility.
VFD Principle
Its a device controls the speed and torque of an electric motor by varying the frequency and voltage supplied to the motor. VFDs are used in a wide range of applications, from simple fan and pumps to complex machines control. It converts industrial frequency power supply into AC power supply of various frequencies to realize variable speed movement of the motor. The control circuit is responsible for completing the control of the main circuit, while the rectifier circuit is responsible for converting alternating current (AC) power into direct current (DC) power. While the inverter circuit converts direct current (DC) power into alternating current (AC) power, the intermediate circuit is responsible for smoothing and filtering the output of the rectifier circuit.
VFD Components
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Rectifier
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DC bus
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Inverter
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Control circuit
Motor Control Center (MCC)
The VFDs in MCC panels are used to control AC motor speed by varying the supply frequency. The VFDs can save energy and reduce operating costs by reducing the speed of the motor when full speed is not required. The MCC panel contains thermal overload relays that protect the motor from overheating by interrupting the power supply when the motor is overloaded.