Basic Electrical

Internal and External Causes for Failure of Equipments

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Internal and External Causes for Failure of Equipment Q. List internal and external causes for failure of equipment’s.  Internal Causes : In some unavoidable situation the machine may have to be run “over loaded” for a longer period which causes temperature rise beyond the permissible limit.  During normal working shot-circuit may occur due to some reasons. … Read more

Do’s and Don’ts to achieve safety while working in substation.

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Do’s and Don’ts to achieve safety while working in substation.  Q. List out Do’s and Don’ts to achieve safety while working in substation. Sr. No. Do’s Don’t 1 Please sign ‘Men working’ or warning boards on the main switch before commencing work. Do not close any switch, unless you are familiar with the circuit which … Read more

Direct, Indirect and Regenerative Type of Testing on Machine

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Direct, Indirect and Regenerative Type of Testing on Machine  Q. Compare direct, indirect and regenerative type of testing. Sr. No Point  Of comparison Indirect Test Direct Test Regenerative Test 1 Loading Method It is a not load indirect test. It is a direct load test. It is an indirect back to back or regenerative test. … Read more

Procedure for Developing Preventive Maintenance Schedule.

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Procedure for Developing Preventive Maintenance Schedule Q. Explain procedure for developing preventive maintenance schedule.  Following points are firstly considered prior to prepare a final preventive maintenance schedule.  Too frequent inspections – will cause waste of time and will not be economical. Too less frequency will invite failure of operation of machine ; and it will … Read more

How Insulation Resistance of a Transformer is Measured

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How Insulation Resistance of a Transformer is Measured Q. State how insulation resistance of a transformer is measured Before commissioning the transformer it is necessary to know that the insulation resistance of a transformer is greater than a specified value, to avoid excessive leakage currents. Megger test for insulation are carried out between windings, between … Read more

Permissible Limits of Variation of Supply Voltage to Motor and Variation of Frequency

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Permissible Limits of Variation of Supply Voltage to Motor and Variation of Frequency Q. Give the permissible limits related to terminal voltage, frequency, temperature rise and speed variation for safe working of electrical machines. Permissible Limits of Variation of Supply Voltage to Motor and Variation of Frequency :  The performance of Electric Machines particularly working … Read more

Advantages of Indirect Testing of Electrical Machines

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Advantages of Indirect Testing of Electrical Machines Q. What are the advantages of indirect testing of electrical machines ?   Advantages of indirect testing of electrical machines :   Power required for testing is less.  Big capacity can be tested without actually loading the machines. Considerable amount of power is saved during testing. Results obtained are reasonably … Read more