Why PT fuse fails protection?

Why PT fuse fails protection?  
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1 Answer

Answer :

Mho relays will mal-operate if PT voltage is lost to the relay, so tripping blocked by sensing PT fuse failure. 
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If a magnetic controller contactor fails to pick up when the coil voltage is applied to the contactor coil, the cause may be _____________. A. overload B. misalignment of the affected contactor contacts C. low spring pressure D. an open contactor coil

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If the illustrated motor fails to start and gives a loud hum when the start button is pushed, the problem is ________. EL-0007 A. one of the phases to the motor is not energized because of an open motor lead B. the 'Disc.sw.' is open C. power to 'L1' at the 'Disc.sw.' is not energized because of a problem with the ship's electrical distribution system D. 'OL1' is open because of 'T1' overload causing the motor to single phase

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Last Answer : Answer: A

Considering the function of the circuit shown in the illustration, what is the purpose of supplying the thrust lever potentiometers with both (+) and (-) 15 volts? EL-0095 A. To select which lever (bridge or engine room) is active. B. So the circuit can differentiate between ahead and astern commands. C. To provide an alternate voltage supply if the other fails. D. So as to automatically select the position of Relay #

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If a magnetic controller relay fails to drop out when the coil voltage is removed from the relay, the probable cause may be _____________. A. excessive spring tension B. overvoltage C. excessive current D. welded contacts

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Last Answer : Answer: D

If the pointer fails to return to zero when a megger is disconnected, the _____________. A. pointer is stuck B. hair springs are burned out C. megger is out of calibration D. megger is operating normally

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What happens when the centrifugal starting switch fails to open?

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Last Answer : Ans: If the starting switch fails to open when needed, then the starting winding will overheat and burn out and motor will not start next time.

What could be the reasons if a 3-phase synchronous motor fails to start?

Description : What could be the reasons if a 3-phase synchronous motor fails to start?

Last Answer : It is usually due to the following reasons a. Voltage may be too low. b. Too much starting load. c. Open circuit in one phase or short circuit. d. Field excitation may be excessive

A synchronous motor starts as usual but fails to develop its full torque. What could it be due to?

Description : A synchronous motor starts as usual but fails to develop its full torque. What could it be due to?

Last Answer : a. Exciter voltage may be too low. b. Field spool may be reversed c. There may be either open-circuit or short-circuit in the field.

Booster transformer should never: a) Have fuse in the HV winding b) Be left open circuited c) Be left closed circuited d) None of the above

Description : Booster transformer should never: a) Have fuse in the HV winding b) Be left open circuited c) Be left closed circuited d) None of the above

Last Answer : Ans: B

Which one of the following applications software’s is used to obtain an accurate root locus for? a) LISP b) MATLAB c) dBase d) Oracle Ans: B 6.Lenz devised a rule to find out direction of a)current induced in a circuit b)electromagneticdifference c)potential difference d)flow of power in fuse

Description : Which one of the following applications software’s is used to obtain an accurate root locus for? a) LISP b) MATLAB c) dBase d) Oracle Ans: B 6.Lenz devised a rule to find out direction of a)current induced in a circuit b)electromagneticdifference c)potential difference d)flow of power in fuse

Last Answer : Ans: A

When changing fuses, you should always _____________. A. wear rubber boots B. use a fuse puller C. stand on a rubber mat D. wear safety glasses

Description : When changing fuses, you should always _____________. A. wear rubber boots B. use a fuse puller C. stand on a rubber mat D. wear safety glasses

Last Answer : Answer: B

Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to remove fuse from the circuit. C. Replace blown fuse with one of equal voltage and ampere capacity. D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.

Description : Which of the following precautions should be taken when a blown fuse, rated at 10 amperes, is replaced? A. Short out the fuse before removing it from the circuit. B. Use needle-nose pliers to ... D. Fuses of 10 ampere rating and less are virtually harmless when energized and may be handled freely.

Last Answer : Answer: C

If a voltage tester is being used to check for defective fuses in the circuit, shown in the illustration, which of the readings will indicate that fuse #2 is open? EL-0062 A. C-B full voltage B. A-D full voltage C. A-D no voltage D. C-B no voltage

Description : If a voltage tester is being used to check for defective fuses in the circuit, shown in the illustration, which of the readings will indicate that fuse #2 is open? EL-0062 A. C-B full voltage B. A-D full voltage C. A-D no voltage D. C-B no voltage

Last Answer : Answer: C

If fuse 'F-1' in the illustrated schematic diagram opens, ____________. EL-0017 A. the motor will run slowly B. 'A-1' and 'A-2' will open C. the motor will not start D. the start button will jam in the closed position

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Last Answer : Answer: C

In the lighting distribution circuit shown in the illustration, if all switches are closed and fuse 'F2' were to open, all lights on branches ____________. EL-0013 A. '1', '2', and '3' would go out B. '1' and '3' would would burn dimly, while branch '2' would burn normally C. '1', '2', and '3' would burn dimly D. '1' and '3' would go out, while branch '2' would remain lit

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Last Answer : Answer: D

The schematic diagram shown in the illustration uses symbol 'A' to represent a/an _________. EL-0011 A. non-renewable fuse link B. circuit breaker coil C. overload relay coil D. thermal overload heater

Description : The schematic diagram shown in the illustration uses symbol 'A' to represent a/an _________. EL-0011 A. non-renewable fuse link B. circuit breaker coil C. overload relay coil D. thermal overload heater

Last Answer : Answer: D

In order to safely carry out repairs to a generator circuit breaker, it must be isolated from the bus. This is accomplished by opening the _____________. A. reverse power relay B. bus disconnect link C. generator bus fuse connections D. power directional relay

Description : In order to safely carry out repairs to a generator circuit breaker, it must be isolated from the bus. This is accomplished by opening the _____________. A. reverse power relay B. bus disconnect link C. generator bus fuse connections D. power directional relay

Last Answer : Answer: B