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

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Losses which occur in rotating electric machines and do not occur in transformers are friction and windage losses.

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Friction losses windage losses 
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Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in?

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Two transformers are connected in parallel. These transformers do not have equal percentage impedance. This is likely to result in loading of the transformers not in proportion to their kVA ratings.

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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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In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are?

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In a given transformer for a given applied voltage, losses which remain constant irrespective of load changes are hysteresis and eddy current losses.

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In case of D.C. machines, mechanical losses are primary function of speed.

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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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Reduction in core losses and increase in permeability are obtained with transformer employing?

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Reduction in core losses and increase in permeability are obtained with transformer employing core built-up of laminations of cold rolled grain oriented steel.

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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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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 two conditions for parallel operation of 3-phase transformer.

Answer :

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

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In any rotating machine that part which houses the conductors and in which e.m.f. induced is to be utilised is called armature.

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If the percentage impedances of the two transformers working in parallel are different, then?

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If the percentage impedances of the two transformers working in parallel are different, then parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load.

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Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is?

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Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is approximately equal to 1.

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Distribution transformers are generally designed for maximum efficiency around 50% load.

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Power transformers are generally designed to have maximum efficiency around near full-load.

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State advantages of rotating field type alternators. 

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UNIT 1 fundamentals of AC rotating machine Contents 1.1 Introduction 1.2 Advantages 1.3 Parts of AC machines 1.4 Synchronous speed 1.5 AC winding 1.6 Winding factor (Coil pitch and distributed winding) 1.7 Distribution factor 1.8 EMF equation of alternator or generator 1.9 Numericals 1.10 Harmonic 1.11 Slot harmonics 1.12 Harmonics minimization

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1.2 Advantages: In practices most of alternator have rotating magnetic field type construction with stationary armature due to following reason. The generation level of AC voltage may be in the range ... at high speed. Only two Slip rings are required to excited the field by AC supply.

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The slip of 400 V, three phase, 4 -pole induction motor when rotating at 1440 rpm is 

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what is mean by rotating transformer ?

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