Manish Kumar Saini has Published 922 Answers

Critical Resistance of a DC Shunt Generator

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 10:25:20

Critical Field Resistance of DC Shunt GeneratorThe critical field resistance (RC) of a DC shunt generator is defined as the maximum field circuit resistance with which the shunt generator would just excite.The voltage build-up in a shunt generator depends upon field circuit resistance. If the field circuit resistance is R1, ... Read More

Cooling Methods of a Transformer

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 10:21:26

When the transformer is in operation, heat is generated due to copper losses in the windings and iron losses in the core. The removal of heat from the transformer is known as cooling of the transformer.Transformer Cooling MethodsFor the dry type transformersAir Natural (AN) CoolingAir Forced (AF) or Air Blast ... Read More

Construction of a Transformer – Core Type and Shell Type

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 10:18:14

The transformers are designed such that it approaches the characteristics of an ideal transformer. For this, following design considerations are incorporatedThe core is made of magnetic materials (like silicon steel) which have high permeability and low hysteresis loss. Also, the core is made laminated to reduce the eddy current loss. ... Read More

Commutation in DC Machines – Resistance Commutation, Voltage Commutation, Compensating Windings

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 10:13:24

In DC machines, there are mainly three methods to obtain good commutation. They areResistance CommutationVoltage CommutationCompensating WindingsResistance CommutationIn the resistance commutation method of improving commutation, the high resistance carbon brushes are used. This increases the resistance between the contact of commutator segments and brushes. This high contact resistance has the ... Read More

Characteristics of DC Motors – Shunt, Series and Compound Motors

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 10:05:38

The performance of a DC motor is given by the relation among the armature current, torque and speed. These relations are given graphically in the form of curves, which are called as characteristics of DC motors. These characteristics show the behaviour of the DC motor under different load conditions.Following are ... Read More

Characteristics of DC Generators – Series, Shunt and Compound

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 09:59:43

Characteristics of DC GeneratorsThe speed of a DC generator is made constant by the prime mover. Under such conditions, the performance of the generator is given by the relation among the excitation, terminal voltage and load. These relations are given graphically in the form of curves, which are called as ... Read More

Back EMF and Its Significance in DC Motors

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 09:27:32

Since the armature of a DC motor rotates in a magnetic field, an emf is induced in the conductors of the armature due to electromagnetic induction (as in a generator). This induced emf acts in the opposite direction to the applied voltage (according to Lenz’s law) and hence is known ... Read More

Armature Reaction in a DC Generator

Manish Kumar Saini

Manish Kumar Saini

Updated on 13-Aug-2021 09:21:41

Armature ReactionThe current flowing through the armature conductors creates a magnetic field, which is called as armature flux. This armature flux distorts and weakens the magnetic flux produced by the main poles. This effect of armature flux on the main flux is known as armature reaction.Case 1Consider a two pole ... Read More

Output of an Autotransformer and Saving of Copper in Transformer

Manish Kumar Saini

Manish Kumar Saini

Updated on 12-Aug-2021 13:19:42

Working of AutotransformerThe connection diagram of an ideal step-down autotransformer is shown in the figure. In which the winding ab is the primary winding having N1 turns and the winding bc is the secondary winding having N2 turns. Here, the current I1 is the input primary current and the current ... Read More

Open Circuit and Short Circuit Test of Transformer

Manish Kumar Saini

Manish Kumar Saini

Updated on 12-Aug-2021 13:12:18

The open-circuit test and the short-circuit test being performed on a transformer to determine the circuit parameters, efficiency and the voltage regulation without actual loaded of the transformer. The open-circuit and short-circuit tests give more accurate results than those are obtained by performing the measurements on a fully loaded transformer. ... Read More

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