Why CT operated over load relay is using for loads of high acceleration time upto 30 seconds? How it getting back?

Why CT operated over load relay is using for loads of high acceleration time upto 30 seconds? How it getting back?
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The saturable current transformers linearly transforms the current upto twice the set current, but above this value the transformer core gets saturated and the secondary current is proportionally less. Thus these relays permit heavy starting conditions of motors and offer dependable protection against overload. When current reduces the core gets de-saturated, as material design is such. 
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Related questions

The boundary of the protective zone is determined by the (A) Location of CT (B) sensitivity of relay used (C) Location of PT (D) None of these

Description : The boundary of the protective zone is determined by the (A) Location of CT (B) sensitivity of relay used (C) Location of PT (D) None of these

Last Answer : Ans: B The boundary of the protective zone is determined by the sensitivity of relay used. If the relay is more sensitive, the protective zone will be increased.

Which of the following statements represents the main difference between a relay and a contactor? A. Contactors control current and relays control voltage. B. A relay is series connected and a contactor is parallel connected. C. Contactors can handle heavier loads than relays. D. Contactors are made from silver and relays are made from copper.

Description : Which of the following statements represents the main difference between a relay and a contactor? A. Contactors control current and relays control voltage. B. A relay is series connected and a contactor ... loads than relays. D. Contactors are made from silver and relays are made from copper.

Last Answer : Answer: C

In accordance with Coast Guard Regulations (46 CFR), each battery operated relay-controlled lantern must _____________. A. be readily portable B. contain a dry cell battery having a minimum capacity of 10 amp hours C. have an automatic battery charger to maintain the battery in a fully charged state D. all of the above

Description : In accordance with Coast Guard Regulations (46 CFR), each battery operated relay-controlled lantern must _____________. A. be readily portable B. contain a dry cell battery having a minimum capacity of ... automatic battery charger to maintain the battery in a fully charged state D. all of the above

Last Answer : Answer: C

The contacts operated by the D.C. relay coil shown in the illustration are located in the schematic diagram prints at coordinates ____________. EL-0100 A. '41Y' on this page B. '52M52M' and '52H35M' C. '57R' on this page D. '52N' on page '57R'

Description : The contacts operated by the D.C. relay coil shown in the illustration are located in the schematic diagram prints at coordinates ____________. EL-0100 A. '41Y' on this page B. '52M52M' and '52H35M' C. '57R' on this page D. '52N' on page '57R'

Last Answer : Answer: C

The vertical dotted line connecting the small circular symbols at coordinates '05L', '09L', '13L', '21L', '25L', etc., shown in the illustration, indicate that all _______________. EL-0100 A. contacts are operated by the same relay coil B. screw connections are on terminal board 'TB2' C. wires are grounded at both ends of the line D. wires have a common shield

Description : The vertical dotted line connecting the small circular symbols at coordinates '05L', '09L', '13L', '21L', '25L', etc., shown in the illustration, indicate that all _______________. EL-0100 A. contacts are ... board 'TB2' C. wires are grounded at both ends of the line D. wires have a common shield

Last Answer : Answer: B

What precaution should be taken while removing a current operated relay when the equipment is in service?

Description : What precaution should be taken while removing a current operated relay when the equipment is in service?

Last Answer : Ensure that the CT is not getting opened by shorting the appropriate terminals. (Eventhough the terminals are automatically shorted once relay is removed the above point may carried out to ensure the same) 

Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed? (A) Wet grinding in low viscous suspension (B) Wet grinding in high viscous suspension (C) Dry grinding of large particles (upto 1.25 cms) (D) Dry grinding of large particles in un-baffed mills

Description : Actual operating speed of a ball mill may vary from 65 to 80% of the critical speed. Which of the following duties would require the ball mill to be operated at maximum percentage of critical speed? (A) ... of large particles (upto 1.25 cms) (D) Dry grinding of large particles in un-baffed mills

Last Answer : (D) Dry grinding of large particles in un-baffed mills

Why CT is never operated with an open secondary ?

Description : Why CT is never operated with an open secondary ?

Last Answer : CT secondary should never be kept open because it will cause saturation of the core to a high level and very high voltage will appear across the secondary which can breakdown the insulation. One terminal of PT secondary is always grounded to avoid capacitive induction and for human safety

If a particle charges its angular velocity from 30 to 35 rpm in 20 seconds then it has angular acceleration of a.107 dynes b.30 rev/min2 c.10 rev/min2 d.20 rev/min2 e.15 rev/min2

Description : If a particle charges its angular velocity from 30 to 35 rpm in 20 seconds then it has angular acceleration of a.107 dynes b.30 rev/min2 c.10 rev/min2 d.20 rev/min2 e.15 rev/min2

Last Answer : e. 15 rev/min2

Does over load relay give 100% guarantee against the single phasing?

Description : Does over load relay give 100% guarantee against the single phasing?  

Last Answer : No. It depends on the motor load and the motor winding (star or delta).  

Two paralleled alternators are operating near rated load. If one trips out mechanically, which of the listed actions should be taken FIRST? A. Restart the tripped machine immediately. B. Strip the board of all non-vital circuits. C. Start the emergency generator. D. Transfer all vital loads to the emergency bus.

Description : Two paralleled alternators are operating near rated load. If one trips out mechanically, which of the listed actions should be taken FIRST? A. Restart the tripped machine immediately. B. Strip the board ... circuits. C. Start the emergency generator. D. Transfer all vital loads to the emergency bus.

Last Answer : Answer: B

The purpose of 'R6' in the winch circuit shown in the illustration is to _______________. EL-0102 A. maintain dry conditions within the winch brake box B. keep the series field current at a low value during 'fourth and fifth point lowering' C. act as the armature dynamic braking load to assist the winch in stopping D. limit the armature current during lowering operation with heavy loads

Description : The purpose of 'R6' in the winch circuit shown in the illustration is to _______________. EL-0102 A. maintain dry conditions within the winch brake box B. keep the series field current at ... to assist the winch in stopping D. limit the armature current during lowering operation with heavy loads

Last Answer : Answer: C

The operator of electrical motors should keep a constant check on the loads they carry because _____________. A. low loads necessitate frequent insulation cleaning B. exceeding nameplate values shortens useful life C. energy is wasted if full loading is not utilized D. power factor correction methods are load dependent

Description : The operator of electrical motors should keep a constant check on the loads they carry because _____________. A. low loads necessitate frequent insulation cleaning B. exceeding nameplate values shortens ... wasted if full loading is not utilized D. power factor correction methods are load dependent

Last Answer : Answer: B

The total power consumed in a parallel circuit is __________. A. the sum of the powers used in each load (resistor) divided by the number of loads B. always less than the power used in the smallest load C. the sum of the powers used in each individual load D. never more than the power used in the largest load

Description : The total power consumed in a parallel circuit is __________. A. the sum of the powers used in each load (resistor) divided by the number of loads B. always less than the power used in the smallest ... of the powers used in each individual load D. never more than the power used in the largest load

Last Answer : Answer: C

The total power used up in a series circuit is ___________. A. the sum of the powers used in each load (resistor) divided by the number of loads B. the sum of the powers used in each load C. always less than the power used in the smallest load D. never more than the power used in largest load

Description : The total power used up in a series circuit is ___________. A. the sum of the powers used in each load (resistor) divided by the number of loads B. the sum of the powers used in each load C. always less than the power used in the smallest load D. never more than the power used in largest load

Last Answer : Answer: B

If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug

Description : If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug setting multiplier will be

Last Answer : If the fault current is 6000 A, the relay plug setting is 150% and the CT ratio is 400/5, the plug setting multiplier will be 10

If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be

Description : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be

Last Answer : If the fault current is 2000 A, the relay setting is 50% and CT ratio is 400:5, the plug setting multiplier will be 10 A

Two transformers of identical voltages but different capacities are operated in parallel, for satisfactory load sharing: a) Impedances should be equal b) Per unit impedance must be equal c) per unit impedance and X/R ratio must be equal d) Impedance and X/R ratio must be equal

Description : Two transformers of identical voltages but different capacities are operated in parallel, for satisfactory load sharing: a) Impedances should be equal b) Per unit impedance must be equal c) per unit impedance and X/R ratio must be equal d) Impedance and X/R ratio must be equal

Last Answer : Ans: C

In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by ____________. A. a manual override switch B. the weight of the load on the boom C. a spring set brake D. a hand operated band brake

Description : In the event of a power failure during cargo loading operations, the movement of an electric powered cargo winch will be stopped by ____________. A. a manual override switch B. the weight of the load on the boom C. a spring set brake D. a hand operated band brake

Last Answer : Answer: C

If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced torque B. speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop

Description : If a three-phase induction motor is operated under a light load and it develops an open in one of its supply lines, the motor will _____________. A. continue to run, but will vibrate and have reduced ... speed up due to the reduced number of poles C. run cooler due to reduced current flow D. stop

Last Answer : Answer: A

The simplest method of controlling the terminal voltage of compound-wound DC generator is with a _____________. A. hand-operated field rheostat connected in series with the shunt field circuit B. separate exciter in a series with the shunt field C. carbon pile regulator in series with the load D. balance coil diverting neutral current through the shunt field

Description : The simplest method of controlling the terminal voltage of compound-wound DC generator is with a _____________. A. hand-operated field rheostat connected in series with the shunt field circuit B. ... in series with the load D. balance coil diverting neutral current through the shunt field

Last Answer : Answer: A

The torque-speed characteristics of an a.c. operated universal motor has a ______characteristic and it______ be started under no-load condition. (A) inverse, can (B) nearly inverse, can (C) inverse, cannot (D) nearly inverse, cannot

Description : The torque-speed characteristics of an a.c. operated universal motor has a ______characteristic and it______ be started under no-load condition. (A) inverse, can (B) nearly inverse, can (C) inverse, cannot (D) nearly inverse, cannot

Last Answer : Ans: C If torque is zero then speed may exceed up to infinite, that is dangerous for machine and machine can be damaged. N α 1/ T

A tractor engine is operated at full load approximately a) 20-25% of the operating times b) 25-30% of the operating time c) 30-35% of the operating time d) 35-40% of operating time

Description : A tractor engine is operated at full load approximately a) 20-25% of the operating times b) 25-30% of the operating time c) 30-35% of the operating time d) 35-40% of operating time

Last Answer : b) 25-30% of the operating time

Induction cup relay is operated due to changes in (a) current (b) voltage (c) impedance (d) all of the above

Description : Induction cup relay is operated due to changes in (a) current (b) voltage (c) impedance (d) all of the above

Last Answer : (d) all of the above

Induction cup relay is operated due to changes in?

Last Answer : Induction cup relay is operated due to changes in current, voltage, impedance.

If the 'E/P converter' shown in the illustration operated on a range of 1-9 volts and 6-30 PSI, a 5 volt input would yield ______________. EL-0096 A. 9 PSI B. 15 PSI C. 18 PSI D. 24 PSI

Description : If the 'E/P converter' shown in the illustration operated on a range of 1-9 volts and 6-30 PSI, a 5 volt input would yield ______________. EL-0096 A. 9 PSI B. 15 PSI C. 18 PSI D. 24 PSI

Last Answer : Answer: C

If the compressor of 200 cfm loads in 10 seconds and unloads in 20 seconds, the air leakage would be_____ a) 67 cfm b) 100 cfm c) 10 cfm d) 133 cfm

Description : If the compressor of 200 cfm loads in 10 seconds and unloads in 20 seconds, the air leakage would be_____ a) 67 cfm b) 100 cfm c) 10 cfm d) 133 cfm 

Last Answer : a) 67 cfm

The division of the reactive KVA load between paralleled AC generators is initiated by the ______________. A. prime mover governors B. voltage regulators C. phase balance relay D. proportioner

Description : The division of the reactive KVA load between paralleled AC generators is initiated by the ______________. A. prime mover governors B. voltage regulators C. phase balance relay D. proportioner

Last Answer : Answer: B

Diesel generators #1 and #2 are operating in parallel at near full load capacity. Diesel generator #1 suddenly trips out mechanically due to low lube oil pressure. The reverse power relay functions properly and trips generator #1 electrically off the bo A. Start the emergency generator. B. Ascertain cause of the low lube oil pressure. C. Strip the board of all nonvital circuits. D. Secure alarms, reset reverse power relay, and restart #1 engine.

Description : Diesel generators #1 and #2 are operating in parallel at near full load capacity. Diesel generator #1 suddenly trips out mechanically due to low lube oil pressure. The reverse power relay functions ... all nonvital circuits. D. Secure alarms, reset reverse power relay, and restart #1 engine.

Last Answer : Answer: C

A loss of field excitation to an AC generator while operating in parallel will cause it to ____________. A. absorb more and more load due to decreased armature reaction B. lose its load due to the inherent speed droop built into the governor C. smoke and overload due to field flashover as residual field flux changes polarity D. lose its load, begin to motorize, trip out on reverse power relay, and possibly overspeed

Description : A loss of field excitation to an AC generator while operating in parallel will cause it to ____________. A. absorb more and more load due to decreased armature reaction B. lose its load due to ... polarity D. lose its load, begin to motorize, trip out on reverse power relay, and possibly overspeed

Last Answer : Answer: D

An alternator operating in parallel begins to vibrate severely and eventually trips out on the reverse power relay. The cause of the vibration was a result of ______________________. A. the dropping of load by that alternator B. overspeeding of the vibrating alternator C. the alternator was operating out of synchronism D. flashover at the alternator collector rings

Description : An alternator operating in parallel begins to vibrate severely and eventually trips out on the reverse power relay. The cause of the vibration was a result of ______________________. A. the ... C. the alternator was operating out of synchronism D. flashover at the alternator collector rings

Last Answer : Answer: C

Which of the listed procedures is the best way to tell if a motor has become overloaded? A. Measure the current flow and compare it with the motor full load current flow as shown on the nameplate. B. Feel the motor and judge by the temperature. C. Watch for telltale signs of smoke coming from the motor. D. Periodic opening of the O/L relay coil

Description : Which of the listed procedures is the best way to tell if a motor has become overloaded? A. Measure the current flow and compare it with the motor full load current flow as shown on the nameplate. ... Watch for telltale signs of smoke coming from the motor. D. Periodic opening of the O/L relay coil

Last Answer : Answer: A

Why is it a good practice to have the frequency of the incoming alternator adjusted slightly higher than that of the loaded alternator when paralleling two alternators? A. This allows the oncoming machine to accept load immediately. B. This prevents the machine from floating on the line. C. The reverse power relay is prevented from activating. D. All of the above.

Description : Why is it a good practice to have the frequency of the incoming alternator adjusted slightly higher than that of the loaded alternator when paralleling two alternators? A. This allows the oncoming machine to ... line. C. The reverse power relay is prevented from activating. D. All of the above.

Last Answer : Answer: D

If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B. starting winding will burn out C. motor will immediately stall under load D. motor torque will be above normal at rated speed

Description : If the centrifugal switch or relay used for cutting out the starting winding of a split-phase induction motor fails to open once the motor is in operation, the _____________. A. motor will overspeed B ... C. motor will immediately stall under load D. motor torque will be above normal at rated speed

Last Answer : Answer: B

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 : 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

Last Answer : Answer: D

In the illustration, if one of the devices labeled 'TURB' should fail the ___________. EL-0003 A. device labeled 'EXC' will drive the alternator B. device labeled 'BKR' for that alternator should automatically open because of the reverse power relay C. operator must open all the devices labeled 'BKRS' to reduce the load on the remaining turbo-alternator D. emergency generator should automatically start and be placed on line to supply emergency load centers

Description : In the illustration, if one of the devices labeled 'TURB' should fail the ___________. EL-0003 A. device labeled 'EXC' will drive the alternator B. device labeled 'BKR' for that ... -alternator D. emergency generator should automatically start and be placed on line to supply emergency load centers

Last Answer : Answer: B

As shown in the illustration, when the 'speed control' system is in 'SPLIT' _______________. EL-0096 A. Relays #1, #5 and #8 are not used B. the 'slew rated controller' is grounded through Relay #6 C. the RPM 'function generator' and 'thrust levers' have no control D. the 'E/P converters' are bypassed and air is fed directly to the governors via the 'load sharing valve'

Description : As shown in the illustration, when the 'speed control' system is in 'SPLIT' _______________. EL-0096 A. Relays #1, #5 and #8 are not used B. the 'slew rated controller' is grounded through Relay ... E/P converters' are bypassed and air is fed directly to the governors via the 'load sharing valve'

Last Answer : Answer: C

Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in armature reaction are compensated for by the __________ A. governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Description : Regarding an AC generator connected to the main electrical bus; as the electric load and power factor vary, a corresponding change is reflected in the generator armature reaction. These changes in ... . governor speed droop setting B. voltage regulator C. balance coil D. phase-balance relay

Last Answer : Answer: B

Where CT secondary of 1A we are using?

Description : Where CT secondary of 1A we are using?

Last Answer : For long distance current transmission, to reduce the IR drop.  

What is the main purpose of using Stress breakers: A. To distribute the load between teeth and ridges B. To distribute the load between the clasps and the face end of the saddle C. It relieves the abutment tooth of occlusal loads that may exceed their physiologic strength

Description : What is the main purpose of using Stress breakers: A. To distribute the load between teeth and ridges B. To distribute the load between the clasps and the face end of the saddle C. It relieves the abutment tooth of occlusal loads that may exceed their physiologic strength

Last Answer : C. It relieves the abutment tooth of occlusal loads that may exceed their physiologic strength

Discuss the effect of acceleration factor in load flow study.

Description : Discuss the effect of acceleration factor in load flow study.

Last Answer : The acceleration factor is a real quantity and it modify the magnitude of voltage alone.

In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in parallel only C. the prime mover speed is to remain constant through varying loads in parallel or single operation D. the circuit breaker is closed for that generator

Description : In the illustration, the contacts between terminals 26 and 27 should be closed when _________. EL-0046 A. using one generator in isochronous mode only B. using two or more generators in ... through varying loads in parallel or single operation D. the circuit breaker is closed for that generator

Last Answer : Answer: C

Routine A.C. motor maintenance should include periodic ______________. A. thermometer readings at normal loads to detect abnormal temperature rises B. inspection of the motor's internals for loose rotor bars or field poles C. bearing replacement each year using sealed units if available D. all of the above

Description : Routine A.C. motor maintenance should include periodic ______________. A. thermometer readings at normal loads to detect abnormal temperature rises B. inspection of the motor's internals for loose rotor bars ... C. bearing replacement each year using sealed units if available D. all of the above

Last Answer : Answer: A

Why core balance CT is preferred over residual connected CT’s to sense earth fault in 6.6 kV feeders?

Description : Why core balance CT is preferred over residual connected CT’s to sense earth fault in 6.6 kV feeders?

Last Answer : a) To avoid relay mal-operation due to CT saturation b) Better sensitivity is got. c) High pickup and TMS avoided in IDMT earth fault relay. 

What is over voltage interturn test for CT?

Description : What is over voltage interturn test for CT?

Last Answer : With secondary open, pass rated current in primary for 1 min. Then check secondary for insulation. 

Electric ovens using heating elements of _______________ can produce temperature upto 3000°C. (A) Nickel (B) Graphite (C) Chromium (D) Iron

Description : Electric ovens using heating elements of _______________ can produce temperature upto 3000°C. (A) Nickel (B) Graphite (C) Chromium (D) Iron

Last Answer : Ans: C Chromium has high melting point.

If a soil undergoes a change in shape and volume by application of external loads over it, but recovers its shape and volume immediately after removal of the load, the property of the soil is said to be (A) Resilience of soils (B) Elasticity of soils (C) Compressibility of soils (D) None of these

Description : If a soil undergoes a change in shape and volume by application of external loads over it, but recovers its shape and volume immediately after removal of the load, the property of the soil is said to ... Resilience of soils (B) Elasticity of soils (C) Compressibility of soils (D) None of these

Last Answer : Answer: Option B

But is it advisable to keep the secondary of CT in open conditions? Will not induce very high voltage?

Description : But is it advisable to keep the secondary of CT in open conditions? Will not induce very high voltage?

Last Answer : If the CT has only one secondary winding, we should keep it always short cktd for safety, but if the CT has multiple secondary, then if one secondary voltage is kept limited by suitable loading, then the other secondary voltage is eventually limited proportionately.