Variable Frequency Drive(VFD)

What is VFD?

VFD is an adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage.

What is VFD?

Variable speed drive (VSD)AC driveAdjustable frequency drive

(AFD)

BASIC COMPONENTS OF VFD:

Input section draws AC electric power from the utility

Rectifier section converts the AC into DC power.

DC Busthe true link between the converter and inverter sections of the drive. Any ripple must be smoothed out before any transistor switches “on”. If not, this distortion will show up in the output to the motor.

Inverter section converts DC back into a controllable AC waveform.

Main Objective of the VFD

To vary the speed of the motor while providing the closest approximation to a sine wave for current.

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

RECTIFIER

PositiveDC Bus

NegativeDC Bus

+

-

INVERTER

Area Under The Square-Wave PulsesApproximates The Area Under A Sine Wave

Frequency

Volta

ge

How Often You Switch From PositivePulses To Negative Pulses DeterminesThe Frequency Of The Waveform

Frequency = 30Hz

Frequency = 60Hz

ADVANTAGES OF VFD

• energy savings

• low motor starting current

• reduction of thermal and mechanical

• stresses on motors and belts during starts

• simple installation

• lower KVA

• VFD installation is as simple as connecting the

power supply to the VFD.

APPLICATIONS:• Energy savings on most pump and fan applications. • Better process control and regulation. • Speeding up or slowing down a machine or process.• Protection from overload currents• Safe Acceleration