Answer / rajesh

In any process plant or factory , we need motor to move /
compress / pump/blow/ventilate etc . in motors we have dc ,
ac , synchronous motors . dc motor are not as efficient as
ac 3 phase motor , hence we use ac motor .

now a 3 ph ac motor has nonlinear speed /torque
characteristics u can see in any website . this means that
for any torque desired speed is not constant .to achieve
this we have to keep supply voltage to frequncy constant .
this is done by vfd . as such variation of suply voltage is
impossible hence we vary frequency .
3 types 1.pwm 2. direct control etc

Answer / faiyaz ahmad

VFD-vfd stand for variable frequency drive-its controller which is used to control the motor turbine and cooler fan in the process industries its control the speed of motor and cooler fan it can increase the speed and decrease the speed of motor.

Hi Friends i am going to write BARC written test by this month 20th (20-5-2008). So please if any body knows the details about this or having previous question papers pls mail me to kkumarei@gmail.com. For Suggestions give one message to 9962122264

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