Explain about elementary direct-current machines, Electrical Engineering

Assignment Help:

Q. Explain about Elementary Direct-Current Machines?

A preliminary discussion of dc machines, including Equations. The location of the brushes on the commutator arrangement connected to the armature winding ensures that the rotor and stator mmf axes are at all times at right angles to one another, as shown in Figure. The expression for torque given by Equation is applicable to the dc machine, provided the constant K is adjusted for the nonsinusoidal mmf distributions and sin δ is made equal to unity. Not only are the conditions for constant torque fulfilled, but also the condition for maximum torque and hence for maximum energy conversion is satisfied, since δ = ± π/2, depending upon whether generator or motor action occurs for a given direction of rotation.

1098_Explain about elementary direct-current machines.png

Since both armature and field circuits carry direct current in the case of a dcmachine, they can be connected either in series or in parallel. When the armature and field circuits are connected in parallel, the machine is known as a shunt machine. In the shunt machine, the field coils are wound with a large number of turns carrying a relatively small current. When the circuits are connected in series, the machine is known as a series machine. The field winding in the series machine carries the full armature current and is wound with a smaller number of turns. A dc machine provided with both a series-field and a shunt-field winding is known as a compound machine. In the compoundmachine, the series fieldmay be connected either cumulatively, so that itsmmf adds to that of the shunt field, or differentially, so that the mmf opposes. The differential connection is used very rarely. The voltage of both shunt and compound generators (or the speed, for motors) is controlled over reasonable limits by means of a field rheostat in the shunt field. The machines are said to be self-excited when the machine supplies its own excitation of the field windings, as in the cases just defined. The field windings may be excited separately from an external dc source, however. A small amount of power in the field circuit can control a large amount of power in the armature circuit. The dc generator may then be viewed as a power amplifier.


Related Discussions:- Explain about elementary direct-current machines

Examine the features of a typical pc motherboard, Q. Examine the features o...

Q. Examine the features of a typical PC motherboard? The purpose of this experiment is to examine the features of a typical PC motherboard, including: CPU and co-process

Potentiometric type dvm, Potentiometric type DVM: A potentiometric type of...

Potentiometric type DVM: A potentiometric type of DVM, employs voltage comparison technique. In this DVM the unknown Voltage is compared with a reference voltage value is fixed by

Fields winding - motor control , Fields Winding It produces the workin...

Fields Winding It produces the working  flux, this is also  called exciting winding.

Explain how ccitt standards help in building the base band, Q. Discuss FDM ...

Q. Discuss FDM and illustrate how CCITT stndards help in building the base band? Ans: Frequency Division Multiplexing: It is the process of combining numerous informatio

Banking system , banking system is the collection of financial entities, in...

banking system is the collection of financial entities, infrastructure and practices which support financial transactions . system tech is a software system to handle their transa

CMA instruction of 8051., if contents of accumulator are all one''s then re...

if contents of accumulator are all one''s then result would be zero so Z flag should be affected and same if all zero''s.....but here it is written that no flags is affected...

Evaluate the current flowing in the direction from b to a, Q. A beam contai...

Q. A beam containing two types of charged particles is moving from A to B. Particles of type I with charge +3q, and those of type II with charge -2q (where -q is the charge of an e

Semiconductors, Why do potential barriers breaks when a breakdown voltage i...

Why do potential barriers breaks when a breakdown voltage is application to semiconductor

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd