Govt. Exams
Entrance Exams
Armature reaction is caused by armature MMF which distorts the main magnetic field, reduces net flux, and causes commutation issues. Compensation is needed through commutating poles.
Ns = 120×50/8 = 750 rpm. Slip s = (750-720)/750 = 30/750 = 0.04 or 4%.
Maximum torque occurs at slip sm = R2/X2. This is crucial for motor design and performance analysis.
Indian Grid Code 2023 specifies that when reactive power reserves fall below 15% of the available reactive power limit, emergency corrective measures must be initiated to prevent voltage collapse.
The transient stability limit is always greater than the steady-state stability limit. A system can maintain transient stability even after a disturbance that would violate steady-state stability.
Loss of synchronism occurs when the generator rotor continuously accelerates because decelerating torque never becomes greater than accelerating torque, preventing the rotor from returning to synchronous speed.
QC = (V²/Xc) where Xc = 1/(ωC), Total C = 0.008 × 200 = 1.6 µF, Qc = (132000)² × 2π × 50 × 1.6×10^-6 = 256.7 MVAR
IEEE 1588-2019 specifies ±0.01 Hz accuracy for steady-state frequency measurement in PMUs used for power system monitoring.
The swing equation 2H(d²δ/dt²) = Pm - Pe - D(dδ/dt) describes rotor angle dynamics, where H is inertia constant, Pm is mechanical power, Pe is electrical power, and D is damping coefficient.
Voltage instability occurs when reactive power demand exceeds generation and compensation capabilities, leading to progressive voltage decline and potential collapse.
