Description : The purpose of a short circuit forcing module (short time trip) installed in a branch line is to provide ____________. A. high speed clearance of low impedance short circuits in the branch B. ... C. isolation of short circuits by selective tripping of branch circuit breakers D. all of the above
Last Answer : Answer: D
Description : What are the three time delay ratings for circuit breakers?
Last Answer : Instantaneous, short time delay, and long time delay.
Description : What is selective tripping and why is it used?
Last Answer : . It is the use of time delay ratings to cause the circuit breaker closest to the faulty circuit to trip. This isolates the faulty circuit without affecting other circuits.
Description : Why under voltage tripping of motor is incorporated in motor feeder breakers?
Last Answer : The under voltage can occur in case of bus fault. If the motors are kept connected they will feed the fault which may cause the damage. Due to the back feeding from the motor the motor will slow down ... case pht motor will not rotate for the designed 3 minute period in case of bus under voltage).
Description : A ground is indicated by the ground-detecting system on the main electrical switchboard. The FIRST step in locating the actual ground is to _____________. A. close all circuit breakers in ... ground detection system indicates normal C. change over generators D. check each circuit with a megohmmeter
Last Answer : Answer: B
Description : In accordance with Coast Guard Regulations (46 CFR), a circuit breaker located in the machinery space and installed in a 440V AC system must _____________. A. be dependent upon mechanical ... the maximum asymmetrical shortcircuit current available at the point of application D. all of the above
Last Answer : Answer: C
Description : The ground indicating light on the main electrical switchboard is indicating a ground. The best procedure for locating the grounded circuit is to _____________. A. trace the circuit paths while looking for ... a time, until the lights no longer indicate a ground D. check all circuits for continuity
Description : As a result of a mechanical malfunction in one of the ship's service generators operating in parallel, you must secure that generator. In order to prevent a possible overload to the ... feeder circuit breakers, the malfunctioning prime mover turbine throttle trip, and the generator circuit breaker.
Description : In general AC distribution systems, arc interruption in vacuum circuit breakers are designed to function in a time period of (a) One cycle (b) Two to three cycles (c) Within ten cycles (d) None of the above
Last Answer : In general AC distribution systems, arc interruption in vacuum circuit breakers are designed to function in a time period of One cycle
Description : In a circuit such as that shown in figure 3-16, if R1 has a value of 50 ohms and R2 has a value of 250 ohms and the input signal has a value of +10 millivolts, what is the value of the output signal?
Last Answer : 60 millivolts.
Description : In a circuit such as that shown in figure 3-15, if R1 has a value of 100 ohms and R2 has a value of 1 kilohm and the input signal is at a value of + 5 millivolts, what is the value of the output signal?
Last Answer : 50 millivolts.
Description : How is amplification achieved in the circuit shown in figure 2-43?
Last Answer : By varying the amount of capacitance in the circuit
Description : What effect does the internal resistance have on the rest of the circuit shown in figure 3-60?
Last Answer : Because of the 2-volt drop across the internal resistance, only 48 volts is available for the rest of the circuit.
Description : What is the total resistance of the circuit shown in figure 3- 60?
Last Answer : 25Ω
Description : What is the total resistance of the circuit shown in figure 3- 59? (Hint: Redraw the circuit to simplify and then use equivalent resistances to compute for RT.)
Last Answer : 4Ω
Description : What is the name given to the "picture" of a circuit such as the one shown in figure 3-2?
Last Answer : A schematic diagram.
Description : What type of frequency meter is shown and what is the value indicated for each meter in figure 1-52?
Last Answer : A) Vibrating-reed, 60Hz. (B) Moving-disk, 58 Hz.
Description : What type of meter is shown and what is the value of the quantity being measured for each meter in figure 1-51?
Last Answer : (A) Megger (megohmmeter), infinity; (B) Wattmeter, 9.5 kilowatts (9,500 watts). (C) Watt-hour meter, 2.693 megawatt-hours 2,693 kilowatt-hours) (2,693,000 watt-hours).
Description : What meter reading is shown on each multimeter in each part of figure 1-50?
Last Answer : (A) 410 mA dc; (B) 3.9 mA ac; (C) -22 V dc; (D) 600 V ac; (E) 1.4 V ac; (F) 1.9 kohms
Description : In the power amplifier shown in figure 2-10, what two signals are mixed to produce the output signal?
Last Answer : Local oscillator and coherent oscillator.
Description : Which connector should you use to connect the (a) power source and (b) load to the fuseholder shown in figure 2-12(A)?
Last Answer : a. Center connector b. Outside connector
Description : For a traction transformer circuit breaker state: 1) Rated current and rupturing capacity 2) Any two tests it should be capable of withstanding 3) Overall tripping time and relay time.
Last Answer : Ans: 1) Rated current --- 750 A and Rupturing capacity --- 500 MVA 2) Any two tests it should be capable of withstanding --- Breaking test , Reclosing test , Endurance test ( any two ) 3) Overall tripping time --- 0.14 sec and Relay time --- 0.04 sec
Description : Give an example of a device you could protect with each type of time delay fuse.
Last Answer : Delay-Motors, solenoids, or transformers. Standard Automobiles, lighting or electrical power circuits. Fast-Delicate instruments or semiconductor devices.
Description : My (soon-to-be-replaced) air conditioner is frequently tripping the circuit breaker in my apartment. What can I do to prevent this?
Last Answer : answer:A mini-split AC unit will use less power than a regular square version and should help with the problem. However if your problem resides in old wiring with a lower amperage/threshold you might ... every time you want to use it but this has cut my electric bill dramatically. Hope this helps
Description : An AC generator operating in parallel loses its excitation without tripping the circuit breaker. This will __________. A. not affect the faulty generator due to the compensation of the other generators B. ... between the armature and the bus D. cause high currents to be induced in the field windings
Description : A reverse-current relay will prevent AC generator motorization by ____________. A. automatically redirecting the load B. automatically speeding up the prime mover C. tripping the panel board main switch D. tripping the generator circuit breaker
Description : In addition to testing the calibration of a circuit breaker, maintenance should include all of the following EXCEPT ______________. A. changing out of magnetic elements and thermal heaters yearly B. ... for loose or missing parts D. making sure foreign matter does not block tripping element
Last Answer : Answer: A
Description : The arc resulting from the tripping of a circuit breaker is prevented from damaging the contacts by _____________. A. designing the contacts to open slowly B. directing the arc into an ... an inverse timed thermal trip for short circuit currents D. instantaneous magnetic trip for overload currents
Description : Accidental grounds in a shipboard electrical system must be repaired as soon as possible as they will ____________. A. result in immediate power outages B. damage circuit breakers C. appear on the ground detection system D. damage insulation and may cause outages
Description : Air blast circuit breakers for 400 kV power system are designed to operate in (a) 100 microsecond (b) 50 millisecond (c) 0.5 sec (d) 0.1 sec
Last Answer : (b) 50 millisecond
Last Answer : Air blast circuit breakers for 400 kV power system are designed to operate in 50 millisecond.
Description : RADAR means A. Radio detection and rating B. Radio detection and ranging C. Radio distance and ranging D. Radio delay and ranging
Last Answer : B. Radio detection and ranging
Description : As shown in the illustration, the circuit has been on the line for several days when component 'E1' burns out. The operator receives an alarm, switches over 'B' to energize the standby ... than required for the circuit therefore limiting the current through the alarm relay which will not pick up
Description : Due to its construction, the component in figure 'A' shown in the illustration has which of the listed advantages compared to bipolar devices? EL-0078 A. Operates with higher voltages and ... as a controllable rectifier. D. Has very high input resistance and uses practically no gate current.
Description : Undervoltage trips are frequently installed on switchboard circuit breakers to trip ____________. A. out generators in the event of severe arcing or sparking B. out generators when there is reversal of power ... , but continues to run D. out generators when there is low voltage in the main circuit
Description : The purpose of a main switchboard circuit breaker's reverse-power trip is to _____________. A. prevent main circuit overload B. protect the circuit breaker blowout coil C. prevent alternator motorization D. prevent low voltage tripout
Description : What are different types of circuit breakers employed in thermal power plant?
Last Answer : Answer: For low voltage operation 415/220V vacuum circuit breakers or air break circuit breakers are employed. For voltage ratings about 6.6kV and beyond SF6 circuit breakers are employed.
Last Answer : For low voltage operation 415/220V vacuum circuit breakers or air break circuit breakers are employed. For voltage ratings about 6.6kV and beyond SF6 circuit breakers are employed.
Description : Why we need isolation transformers in power circuit ? why cant we use breakers to isolate?
Last Answer : In Isolation transformer is used, if there is change in parameter values of any side, the other side parameters will remain unchanged.
Description : Refer to figure 3-55(A). If the following resistors were replaced with the values indicated: R1 = 900Ω, R3 = 1kΩ, what is the total power in the circuit? What is ER2?
Last Answer : PT = 60 W, ER2 = 10 V.
Description : If the fuse shown on the schematic (figure 3-10) opens, what lights will operate?
Last Answer : Only the brake lights.
Description : A tape pack has gaps in the tape winding as shown in figure 2-5. What causes this condition?
Last Answer : Tape is loosely wound on reel.
Description : A tape pack is buckled and deformed as shown in figure 2- 4. What are three possible causes for this condition?
Last Answer : a. Reel has a distorted hub, b. tape wound over small particle deposited on hub, and c. tape wound on reel with tension increasing toward end of winding.
Description : A triode amplifier similar to the one shown in figure 1-19 has an Ebb -conditions, 1.5 milliamperes of current conducts through the tube. What w
Last Answer : +275 volts
Description : What happens to the path for current when S1 is open as shown in figure 3-2(A)?
Last Answer : The path for current is incomplete; or, there is no path for current with S1 open.
Description : What is the quantity shown on the watt-hour meter in figure 1-46?
Last Answer : 5.945 megawatt-hours, or 5,945 kilowatt-hours, or 5,945, 000 watt-hours.
Description : A 4-bit synchronous counter uses flip-flops with propagation delay times of 15 ns each. The maximum possible time required for change of state will be (A) 15 ns. (B) 30 ns. (C) 45 ns. (D) 60 ns.
Last Answer : Ans: A 15 ns because in synchronous counter all the flip-flops change state at the same time.
Description : What is the current in a circuit with 5 ohms of resistance that uses 180 watts of power?
Last Answer : 6 amperes.
Description : Assertion : In the circuit shown in figure, battery is ideal. If a resistance `R_(0)` is cannected in parallel with R, then power across R will increa
Last Answer : Assertion : In the circuit shown in figure, battery is ideal. If a resistance `R_(0)` is cannected ... . D. If Assertion is false but Reason is true.
Description : Circuit breakers are essentially (a) current carrying contacts called electrodes (b) arc extinguishers (c) circuits to break the system (d) transformers to isolate the two systems (e) any of the above
Last Answer : (a) current carrying contacts called electrodes