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Hopkinson's test on D.C. machines is conducted at full-load.

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Short circuit test on transformers is conducted to determine copper losses.

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An open-circuit test on a transformer is conducted primarily to measure?

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The open-circuit test in a transformer is used to measure

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Sumpner's test is conducted on transformer to determine?

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Sumpner's test is conducted on transformer to determine temprature.

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The purpose of retardation test on D.C. shunt machines is to find out stray losses.

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Satisfactory commutation of D.C. machines requires brushes should be of proper grade and size, brushes should smoothly run in the holders, smooth, concentric commutator properly undercut.

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Brushes of D.C. machines are made of carbon.

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In D.C. machines the residual magnetism is of the order of 2 to 3 percent.

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In D.C. machines fractional pitch winding is used to reduce the sparking.

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In dc machines, the armature windings are placed on the rotor because of the necessity for  (1) electromechanical energy conversion (2) generation of voltage (3) commutation (4) development of torque

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3  Commutation

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Brake test on DC series motor

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DC motor brake test numerical

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A 50 KVA transformer has iron loss 2 kW on full load. Calculate its iron loss at 75% of full load.

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Iron loss is dependent on voltage and independent of load. Hence iron loss at 75% of Load = Iron loss at full load = 2 kW

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Draw the connection diagram of long shunt differential D.C. compound generator.

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Compare core type transformer and shell type transformer on the following parameters. (i) Types of winding used, (ii) Application

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State any two applications of single phase autotransformer.

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Applications of single phase auto transformers: 1) Give small boost to distribution cable to correct the voltage drop. 2) As auto transformer starter for induction motors. 3) As furnace supply ... . 5) In control equipment for single phase locomotives. 6) As dimmer in lighting circuits.

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State any two conditions for parallel operation of 3-phase transformer.

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Conditions for Parallel operation of 3 phase transformer 1) Voltage ratings of both the transformers must be identical. 2) Percentage or p.u. impedance should be equal in magnitude. 3) X/R ratio ... between primary & secondary voltages must be same. 6) Phase sequence on both sides must be same.

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Define transformation ratio in terms of current and voltage.

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(i) Transformation Ratio (K) is defined as the ratio of the primary current to the secondary current.  (ii) Transformation Ratio (K) is defined as the ratio of the secondary voltage to the primary voltage.

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Define: (i) Commercial efficiency of a transformer and  (ii) All day efficiency of a transformer.

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(i) Commercial Efficiency : It is the ratio of output power in watt to the input power in watt. (ii) All day efficiency of a transformer: It is the ratio of output energy in kWh to the input energy in kWh in the 24 hours of the day

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State any four properties of Ideal transformer.

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Properties of Ideal transformer: 1) No losses (iron and copper losses), hence no temperature rise. 2) No magnetic leakage i.e (Coefficient of coupling between primary and secondary windings is unity) 3) Zero winding ... drop i.e. E1 = V1, E2 = V2 5) Efficiency 100 %. 6) Regulation 0 %.

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For a D.C. machines laboratory following type of D.C. supply will be suitable induction motor D.C. generator set.

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Explain the procedure to perform Short Circuit test on single phase transformer with circuit diagram.

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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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i) This test is carried out on 3-ph transformer to identify primary & secondary winding belonging to the same phase. ii) As shown in fig above all primary & secondary phases ... of this test is to check the respective phases of primary & secondary windings in 3-ph transformer

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Explain the open delta (delta-delta) test on transformer.

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Explain the need and steps to conduct the reduced voltage running up test on the three phase induction motor.

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Why phasing out and polarity test is carried out on three phase transformer?

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The phasing out test is carried out to identify the windings (primary and secondary) of corresponding phase of the three phase transformer. The polarity test is carried out to identify the ... identical polarity of the primary and secondary windings of each phase of the three phase transformer.

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The duration of sudden short-circuit test on a synchronous motor is usually about one second.

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A no-load test is performed on a transformer to determine?

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A no-load test is performed on a transformer to determine magnetizing current and loss.

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Write measures to be taken to maintain the insulation resistance of electrical machines to healthy levels.

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What type of motor is used for drilling machines?

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universal motor also used in Handheld power tools, blowers, blenders, vacuum cleaners, polishers and kitchen appliances.universal motor is defined as a motor which may be operated either on direct or single phase AC supply at approximately the same speed and output

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The inertia constants of two groups of machines which do not swing together are M1 and M2. The equivalent inertia constant of the system is

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The inertia constants of two groups of machines which do not swing together are M1 and M2. The equivalent inertia constant of the system is M1M2/M1+M2

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For protection of rotating machines against lightning surges _______ is used.  (1) lightning arrester (2) capacitor (3) combination of lightning arrester and capacitor (4) lightning conductor and arrester

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For protection of rotating machines against lightning surges combination of lightning arrester and capacitor is used. 

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Laminated cores, in electrical machines, are used to reduce?

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Laminated cores, in electrical machines, are used to reduce eddy current loss.

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Silicon steel is used in electrical machines because it has?

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Silicon steel is used in electrical machines because it has low hysteresis loss.

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The speed control of universal motor used for sewing machines is by varying the resistance.

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Exciters of synchronous machines are d.c. shunt machines.

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Losses which occur in rotating electric machines and do not occur in transformers are?

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Friction losses windage losses 

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Polarity Test of Transformer

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What is test bench? Write its applications

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Test Bench: A test bench is used to verify the functionality of the design. We need to stimulate our designs in order to test their functionality. Stimulus in a real system is from an ... the entity under test and to collect output responses. 6. To compare output responses with expected values.

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Slip test is performed to determine :  (A) Slip in an induction motor  (B) Xd and Xq in a salient pole alternator  (C) Synchronous impedance in an alternator  (D) Positive and negative sequence impedances of an alternator

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Slip test is performed to determine :  Xd and Xq in a salient pole alternator 

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If a 5-bus test system contains 6 transmission lines and one transformer, how many non-zero elements are there in the system Y-bus ? (A) 25 (B) 12 (C) 11 (D) 19

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If a 5-bus test system contains 6 transmission lines and one transformer, 19 non-zero elements are there in the system Y-bus.

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Murray loop test can be used for location of both the ground fault and the short-circuit fault.

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During open circuit test of a transformer?

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During open circuit test of a transformer primary is supplied rated voltage.

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Why high voltage test is done?

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What is an insulation resistance test?

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What is a high voltage test?

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