Answer / prasad

In VFD the speed of motor is controlled by changing syn.
speed of motor. This is done by giving variable frequency
supply to motor. In order to keep flux constant (i.e. V/F)
voltage is also reduced alongwith frequency for lower speed
values thereby reducing input current & ultimately power
saving

Answer / magbul

vfd means varieble frequency device, use to change the
speed of motor as per requirement. power is directly
proportional to frequency and to reduce the speed you are
reducing frequency interms power is saving is being done.

Answer / vinod

good amount of power can be saved when controling the speed
of PUMP AND FAN,when using a VFD.
the pump and fan works on AFFINITY LAW ..ie..the speed is
directly proportional to the cube of power.
if 20% of speed is reduced there will be a saving of 50%

Answer / soumya chatterjee

Syn. Speed = (120xf)/P. The basic principal of VFD is to
change the syn. speed of the drive by varying the
frequency. The input sinusoidal voltage gets converted to
DC and againg to AC with lower frequency. The basic
principal also ask for constant flux which is governed by
the ratio V/f. At lower frequency the voltage also reduces
to keep the value of the ratio constant.Which in turn
reduces the input current to the VFD as the voltage at the
incoming terminal of the VFD does not change by VFD
operation.Thereby causes saving in power consumption.

Answer / sumit

VFD acts as a conveter between the motor and main
supply.suppose a motor is carrying a load(coupled to a
pump to lift water )then after sometime load decreases
means requirement of water reduces means pump now needs to
pick less water but torque of motor will have to be same
because pump inertia(m*r*r) and acceleration is constant
stant but now we need to maintain less pressure(to pick
less water) and pressure comes from speed of pump (directly
proportional to motor speed) thus we need to decrease speed
of motor but at the same time as mentioned above constant
torque is must.so decrease voltage to maintain a constant
ratio of voltage/frequency.voltage decreases so currenet
from vfd decreases so line current drawn by vfd from mains
decreases and thus power drawn decreases.and reduction of
speed is done by vfd.

Answer / sathiajith

speed is directly proportional to the cube of power. ie.
20% speed is reduced,50% is the power saving. Also torque
is varying according to the load. Hence current is reduced
while less torque is required.Since it has a soft start,
starting current also can be reduced.

Answer / ankush dhiman

speed is directly proportional to the cube of power. 20%
speed is reduced,50% is the power saving.vfd will be
suitable as per custmor uses.

Answer / kumar.m

Variable frequency drive,if one motor working full speed ex-
chilled water pump but there is no full load if u fix a VFD
in motor frquency propotional to speed when reduce
frequently automaticaly reduce also speed.that time motor
will run depending upon load,this type we can save power.

Answer / a.kossay

VFD IS MORE POWERFUL THAN ANY TOOLS BECAUSE IT USES SOLID
STATE DEVICES LIKE MOSFETS AND IGBTS WICH HAVE A LOWER
POWER CONSUMPTION, BUT IF WE USE RESISTANCE ALOT OF POWER
WILL BE DISSIPATED IN RESISTANCE

I am having dual speed motor of cromton greaves make of 3.7 KW -1400 rpm and 5 KW - 900 rpm. Please let me know groups and winding connction for rewinding purpose.

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