Variable frequency drives (VFDs) are used to control the speed of AC induction motors by varying the frequency of the power supplied to the motor. A VFD system consists of an AC motor, controller, and operator interface. VFDs allow motors to operate at multiple speeds by adjusting the frequency of the power supplied. They provide benefits like energy savings, protection from overloads, and safe acceleration and deceleration of motors. Common applications of VFDs include controlling pumps, fans, conveyors, and compressors.

1. VARIABLE FREQUENCY
DRIVES

2. 1. What is VFD?
2. Purpose Of VFD
3. VFD System
4. Drive Operation
5. Operating Modes
6. AC Induction motor
7. components
8. Advantages
9. Function & Features
10. Applications.

3. Variable Frequency Drives
This technology has several different names such
as :
• Variable speed drives.
• Adjustable speed drives.
• Adjustable frequency drives.
• Frequency converter.

4. • pump and fan applications.
• control and regulation.
• Speeding up or slowing down a machine or
process.
• Protection from overload currents
• Safe Acceleration

7. A variable frequency drives used in a drive
system consisting of the following three main
sub-systems:
• AC Motor.
• Controller.
• Operator Interface.

9. • In variable-speed applications, a dc motor may
be operating in one or more modes:
– Motoring.
– regenerative braking.
– dynamic braking.
– Plugging.
– four quadrants.

10. MOTORING

15. Three-phase motor
operation

16. • Torque is produced as the induction motor
generates flux in its rotating field.
• This flux must remain constant to produce
full-load torque.

17. The speed of the rotating electric field within
the induction motor.
Synchronous Speed = 120 x frequency
no. of motor poles

19. • All VFD’s need a power section that
converts AC power into DC power.
• This is called the converter bridge.
• Sometimes the front end of the VFD, the
converter is commonly a three-phase, full wave-
diode bridge.
• The DC bus is the true link between the
converter and inverter sections of the drive

20. • Vacuum tubes.
• Thyristors (SCR’s).
• Transistors.

21. ms.
Pulse-width-modulated voltage
and current waveform

23. • Control of process temperature and pressure.
• Maintenance costs can be lower.
• Save energy.
• Limit the torque

24. • Set-up Parameters
• The Control Method
• Acceleration or Accel-Ramp Rate
• Automatic Restart
• Stopping Method
• Automatic Signals

25. • Water Supply Pump Application
• Conveyor Application
• Exhaust Fan Application
• Compressor Application

26. • Significant energy savings
• Easy setup & programming
• Better design
• Competitive edge