02-06-2012, 12:12 PM
VARIABLE FREQUENCY DRIVES FOR ID FANS
[attachment=23967]
OBJECTIVES OF VFD’S
Energy saving in pump and fan application
Better process control
Speedup and slow down a machine.
Inherent power factor correlation
Safe acceleration
Protection from over load current
TYPES OF VFD’S
There are three types of vfd’s
1.current source inverter(CSI)
2.voltage source inverter(VSI)
3.cyclo converter
Again current source inverter is classified into two types
1.Pulse width modulation(PWM)
2.Load commutated inverter(LCI)
LCI TYPE VFD
In this type of drive system flow demand signal is received from the control signal due to the change in load conditions
Advantages of LCI
Increased motor life
No limitations on no of starts
No contribution of fault current
LOAD COMMUTATED INVERTER
The LCI is a static , adjustable frequency converter which supplies power to the synchronous motor
LCI system block diagram consist of
Transformer
AC to DC converter
Reactor
DC to AC converter
3-phase synchronous motor
DUAL CHANNEL OPERATION
When the motor can be made to operate in 12-pulse manner ;rather than 6-pulse,the motor harmonic losses can be subsequently reduced
12-pulse operation can be divided into 2 channels in both sides with 30 degrees phase
[attachment=23967]
OBJECTIVES OF VFD’S
Energy saving in pump and fan application
Better process control
Speedup and slow down a machine.
Inherent power factor correlation
Safe acceleration
Protection from over load current
TYPES OF VFD’S
There are three types of vfd’s
1.current source inverter(CSI)
2.voltage source inverter(VSI)
3.cyclo converter
Again current source inverter is classified into two types
1.Pulse width modulation(PWM)
2.Load commutated inverter(LCI)
LCI TYPE VFD
In this type of drive system flow demand signal is received from the control signal due to the change in load conditions
Advantages of LCI
Increased motor life
No limitations on no of starts
No contribution of fault current
LOAD COMMUTATED INVERTER
The LCI is a static , adjustable frequency converter which supplies power to the synchronous motor
LCI system block diagram consist of
Transformer
AC to DC converter
Reactor
DC to AC converter
3-phase synchronous motor
DUAL CHANNEL OPERATION
When the motor can be made to operate in 12-pulse manner ;rather than 6-pulse,the motor harmonic losses can be subsequently reduced
12-pulse operation can be divided into 2 channels in both sides with 30 degrees phase