The document summarizes the basics of variable frequency drives (VFDs). It discusses the four main sections of a VFD: rectifier, intermediate circuit, inverter, and control/regulation. It explains how VFDs work by converting AC power to DC and then pulsing the motor to control its speed. VFDs allow controlling motor speed to match system demands, reducing energy usage. The document provides examples of power savings from installing VFDs on pumps and fans. It outlines important considerations for VFD installation and conclusive advantages like energy savings, better process control, and reduced maintenance.

1. Study of VFD Installations
VARIABLE FREQUENCY DRIVE (VFD)

2. Basics Construction of VFD
● Inside the VFD there are 4 major sections:
➢rectifier (AC/DC Converter),
➢intermediate circuit (DC Link),
➢inverter (DC/AC Converter) and
➢control/regulation (for interface)

3. Working of VFD
● The operation ofthe drive is asfollows:
Power first goesinto the rectifier, where the 3-phaseACisconverted into a rippling
DC voltage. The intermediate circuits then smoothes and holds the DC Voltage at a
constant level or energy source for the inverter. The last section, the inverter, uses the
DC voltage to pulse the motor with varying levels of voltage and current depending
upon the control circuit.
The control section uses the frequency, voltage and phaseangle to control the inverter.

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

6. Function of VFD
●VFD is a system for controlling the rotational speed of a motor by
controlling the frequency of the electrical power supplied to the
motor
●Variable speed drives gradually ramp the motor up to operating
speed to lessen mechanical and electrical stress, reducing
maintenance and repair costs, and extending the life of the motor
and the driven equipment
●Variable-frequency motors on fans save energy by allowing the
volume of air moved to match the system demand. By using VFDs
the system can maintain a constant level or pressure without
continuously cycling the pump or fan on and off. This allows for a
better system control of a level or pressure, instead of cycling
between awide differential

7. How to analyze the necessity for VFD at a
location
●We check for the pump valvesthat are throttled
●If the valve is 30-40 % throttle (closed), then it indicates that
flow required is less
●In such a case VFD can be installed, the valve can be opened
fully and fluid’s speed and flow can be controlled
●For example : Back water pump 2 at PM-1, was running at 1400
rpm taking 22 kW before installation of VFD. But after VFD
installation, it consumes12 kWwhile operating at 1100 rpm.

8. Wiring Diagram of Fan Pump Motor

9. VFD in Drive
Room

10. How VFD works at these locations
●VFDsare installed at Fan Pump motors.
●Fan pump motor responsible for providing stock to the
Head Box
●Head Box requiresacontrol of either head or level
●Control ofalevel or pressure in Head Box is done byVFD
●A reference signal is fed to the VFD and using a
comparator, an error signal is generated based on the
deviation of current value from the reference value. The
controller in the VFD, then, increases/decreases the speed
based on the signalsgenerated

11. How much power saving?
Gen.
MW
ID’s Total
Power (w/o
VFD) (KW)
Total power
(KW) by ID
Fans with VFD
Power
Saving
200 3800 850 2950
240 4150 950 3200
280 4450 1050 3100
320 4800 1250 3550
360 5050 1420 3630
400 5350 1850 3500
440 5600 2500 3100
500 5900 3000 2900

12. Major Considerations while installing a
VFD
●Motor Specifications
●VFDSpecifications
●VFDinput/output current
●Cable Size
●Starting parameters
➢Motor name plate
➢Reference speed
➢Overload current setting
➢Operating option (keypad/remote)
➢V/f ratio control

13. Conclusive advantages of using a
VFD
●EnergySavings
●Better ProcessControl
●Reduced Maintenance
●Higher System Efficiency
●Remote Mounting

14. Thank You