Saturday, 19 December 2015

Electrical Interview:SYNCHRONOUS PHASE MODULAR

                            Electrical synchronous phase modular is basically a synchronous motor operating under no-load,by adjusting the excitation.Excitation is used for controlling electrical reactive power therefore power factor and voltage also controlled.
 over excitation: If excitation of synchronous machine is increased up to over excitation  the synchronous machine act as shunt capacitor(synchronous condenser). According to shunt capacitor operation the synchronous machine delivering lagging reactive power and absorbing leading reactive power from mains.
 under excitation: If excitation of synchronous machine is decreased up to under excitation  the synchronous machine act as shunt reactor. According to shunt reactor operation the synchronous machine absorbs lagging reactive power and delivering leading reactive power from mains.

"under excited synchronous machine is used for compensating ferranti effect in power lines" 

Saturday, 12 December 2015

Electrical Interview:PHANTOM LOADING

                     When the electrical current rating of a energy meter under test is high a test with actual loading arrangements would involve a considerable waste of power. In order to avoid this "phantom loading" is done.
                     Phantom loading consists of supplying the pressure circuit from a circuit of required normal voltage, and the current from a separate low voltage supply. It is possible to circulate the rated current through the current circuit with a low voltage supply as the impedance of the circuit is very low. With this arrangement the total power supplied for the test is that due to the small pressure coil current at normal voltage, plus that due to the current circuit current supplied at low voltage. The total power, therefore, required for testing the meter with phantom loading is comparatively very small.   

Thursday, 10 December 2015

Electrical Interview:TURN ON TIME OF SCR

Delay Time: Practically delay time depends on gate signal magnitude Ig. If Ig increase,initial conduction area increases due this rate of raise of anode current increases therefore Td delay time decreases and turn ON time decrease.                                                                                                                                                          
Raise Time: Raise time in the SCR depends on load parameters for example L is increases the di/dt of SCR decrease and raise time increase then turn ON time increase.                                                  
                 
 Spread Time: Spread time depends on the physical geometrical structure of the device.                                       
                 From above conclusion for inductive loads turn ON time is higher.                

Tuesday, 8 December 2015

Electrical interview:OHM'S LAW


electrical circuit,electrical interview circuit
                  When ever a electrical voltage V(emf) is applied across the basic electrical circuit then the current is flowing in the resistance R, due to the current in the resistance a voltage drop is produced V. According to  ohm's law these are the valid conditions.  
 V proportional I: This statement is correct because the potential difference V is peoportional to the   current flowing in the resistance circuit I.     
  I proportional V(emf): This statement is also correct because the circuit current I is always depends on applied  voltage V