Monday 26 November 2012

A motor problem

Q) A 25 HP 6 Pole 50 Hz 3 phase 960 rpm at full load. I 2 = 35 A, Allowing 250 W as Cu loss in SC gear . 1000 W = Mech losses.
How much is r2?
Ans)

Q) 440 V , 50 Hz, 6P, 3 phase, 

Ans) F2 = 100/60 




Monday 5 November 2012

RL circuit on a AC source.

In the previous post we had seen RL circuit on DC source. Now lets see it on AC source




Transients in power system

Transients in simple circuit

DC Sources:




  • Resistance only
  • Inductance only
  • Capacitance only

  • RC Circuit

  • RLC Circuit:



Sunday 4 November 2012

How to control voltage in power system









































We have seen total grid collapsing twice recently. How voltage is controlled? Lets see in the above diagram


Sources and sink of Reactive power



  • Transmission line
  • Cables
  • Synch. Machines
  • Shunt capacitors and reactors
  • Series capacitors