Related Question
For synchronous motor,
Under excitation - Lagging power factor
Over excitation - Leading power factor
For synchronous generator
Under excitation - Leading power factor
Over excitation - lagging power factor
Related Question
Simple logic of reactance diagram is that simplified equivalent circuit of power system in which the various components of power system are represented by their reactances.
The reactance diagram can be obtained from impedance diagram if all the resistive components are neglected.
In single phase energy meter,
Current coil is made up from thick wire having few no. of turns.
Pressure coil is made up from thin wire having more no. of turns.
Calculation:
Ia1 = 1/3*(Ia + a*Ib + a²*Ic)
= 500 + j150 + (- 0.5 + j*0.866)*(100 – j6000) + (-0.5 - j*0.866)*(– 300 + j600)
= (546.41 + j*156.47) A
Ia2 = 1/3*(Ia + a²*Ib + a*Ic)
= 500 + j150 + (- 0.5 - j*0.866)*(100 – j6000) + (-0.5 + j*0.866)*(– 300 + j600)
= (-146.41 - j*56.47) A
Iao = 1/3*(Ia + Ib + Ic)
= 1/3*(500 + j150 + 100 – j6000 – 300 + j600)
= (100 + j*50) A
Equivalent resistance of the circuit,
Req = (12||18) + 8
Req = 7.2 + 8
Req = 15.2 ohm
Source current = current through 8 ohm resistor, I = Vr/R8
I = 20/8
I = 2.5 A
Supply votage V = I*Req
V = 2.5*15.2
V = 38 V
The neutral point of a generator is usually earthed to facilitate protection of the stator winding and associated system.
Earthing also prevents damaging transient overvoltages in the event of an arcing earth fault or ferro resonance.
For HV generators, impedance is usually inserted in the stator earthing connection to limit the magnitude of earth fault current.