ELECTRICAL ENGINEERING INTERVIEW QUESTION & ANSWER
ELECTRICAL ENGINEERING INTERVIEW QUESTION & ANSWER How do we select the Voltage for Megger in the Electrical System? Rated Voltage of Circuit under Test 220 V 440 V 1000 V 33 KV and Above 765 KV Test Voltage for IR test 500 V 1000 V 2.5 KV 5 KV 5 KV The minimum IR Value is usually recommended as (kV+1) MΩ. Where kV is the Equipment Voltage rating. E.g: In 400 kV rated equipment a periodical 5000 V DC Insulation Resistance (Megger) test is recommended. The minimum criteria of IR value = (400+1) = 401 MΩ is enough . Explain about charging and discharging time of capacitor? Ans: The time constant (T) of a capacitor is Calculated by taking the Circuit Resistance and multiplying it by the circuit Capacitor. For a 1k Ω resistor and 1000 Pfarad Capacitor. The Time Constant should be 1 Second .This is the amount of time it takes for the Capacitor Voltage to increase 63.2% from its present Value to its final value. The discharging circuit provides th