A. slow making and breaking of load circuit contacts
B. foreign matter on the contact surface
C. too low contact pressure
D. all of the above
Related Mcqs:
- In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?
A. have low contact resistance
B. be clean and smooth
C. be of sufficient size and proper shape
D. have all above properties - Admittance relay is __________ relay?
A. impedance
B. directional
C. non-directional
D. none of the above - Induction cup relay is operated due to changes in________________?
A. current
B. voltage
C. impedance
D. all of the above - The arcing contacts in a circuit breaker are made of______________?
A. copper tungsten alloy
B. porcelain
C. electrolytic copper
D. aluminium alloy - The voltage appearing across the contacts after opening of the circuit breaker is called__________voltage
A. recovery
B. surge
C. operating
D. arc
E. none of the above - The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to______________?
A. lubricate the contacts
B. insulate the contacts from switch body
C. extinguish the arc
D. all of the above
E. none of the above - The relay operating speed depends upon_________________?
A. the spring tension
B. the rate of flux built up
C. armature core air gap
D. all of the above - Interruption of large currents by relay requires______________?
A. arc suppressing blow out coils
B. wide separation of the opened contacts
C. high speed opening of contacts
D. all of the above - The under voltage relay can be used for______________?
A. generators
B. busbars
C. transformers
D. motors
E. all of the above - The torque produced in induction type relay (shaded pole structure) is_____________?
A. inversely proportional to the current
B. inversely proportional to the square of the current
C. proportional to the current
D. proportional to square of the current
