MGVCL Exam Paper (30-07-2021 Shift 2)
A short-shunt dc compound generator supplies 50 A at 300 V. If the shunt field resistance, series field resistance and armature resistance are 30 Ω, 0.03Ω, and 0.05 Ω respectively, determine the e.m.f. generated.
Class B trip curve : The MCB with class B trip characteristics trips instantaneously when the current flowing through it reaches between 3 to 5 times rated current. These MCBs are suitable for cable protection.
Class C trip curve: MCB with class C trip characteristics trips instantaneously when the current flowing through it reaches between 5 to 10 times the rated current. Suitable Domestic and residential applications and electromagnetic starting loads with medium starting currents.
Class D trip curve: MCB with class D trip characteristics trips instantaneously when the current flowing through it reaches between Above 10 (excluding 10) to 20 times the rated current. Suitable for inductive and motor loads with high starting currents.
Class K trip curve: MCB with class K trip characteristics trips instantaneously when the current flowing through it reaches between 8 to 12 times the rated current. Suitable for inductive and motor loads with high inrush currents.
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.
MCCB stands for Moulded Case Circuit Breaker. MCB stands for Miniature Circuit Breaker. ELCB stands for Earth Leakage Circuit Breaker RCCB stands for Residual Current Circuit Breaker.
EXAMIANS