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

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

Answer :

No. It depends on the motor load and the motor winding (star or delta).  
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Description : What is the current in single phasing?

Last Answer : 2 times of rated current.

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Last Answer : When one supply is open circuit in a three phase motor.

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Description : What is single phasing?

Last Answer : Single phasing is a condition in three phase motors and transformers wherein the supply to one of the phases is cut off.

Explain the working of single phasing preventer with neat diagram.

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Last Answer : Working of single phasing preventer:  Single phasing preventers are generally used for small / medium capacity motors. Single phasing preventers are connected in secondary of line CTs. These ... contact gets opened which stops the motor to avoid further damage when single phasing occurs. 

Explain single phasing preventer with neat sketch diagram.

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Last Answer : The single phasing relays are used for the protection of three phase motors.

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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.

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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

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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

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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.

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With the help of neat diagram, describe the procedure to carry out phasing out test on a 3 phase transformer. Also state the purpose of conducting this test on 3 phase transformer.

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What is the difference between over voltage relay and over current relay?

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Description : What is the advantage of CMM relay over normal Inv. O/C current relay?

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Why IDMT over current relay is always used as backup?

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Last Answer : It is a self powered inverse time over current and earth fault relay, used for selective phase and earth fault protection in time graded systems for A.C. machines, transformers, feeders ... it rotates the driving torque increases and offsets the changing restraining torque of the control spring. 

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When voltage increases then current also increases then why we need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?

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When a guarantee extends to a single transactions or debt it is called a) Retrospective guarantee b) Specific Guarantee c) Prospective guarantee d) Fidelity guarantee

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