Dc machine, Electrical Engineering

Assignment Help:

In the conventional dc machine (with a closed continuous commutator winding on its armature), for example, full-wave rectification of the alternating voltage induced in individual armature coils is achieved by means of a commutator, which makes a unidirectional voltage available to the external circuit through the stationary carbon brushes held against the commutator surface.The armaturewindings of dcmachines are located on the rotor because of this necessity for commutation and are of the closed continuous type, known as lap and wavewindings. The simplex lap winding has as many parallel paths as there are poles, whereas the simplex wave winding always has two parallel paths. The winding connected to the commutator, called the commutator winding, can be viewed as a pseudostationary winding because it produces a stationary flux when carrying a direct current, as a stationarywindingwould. The direction of the flux axis is determined by the position of the brushes. In a conventional dc machine, in fact, the flux axis corresponds to the brush axis (the line joining the two brushes). The brushes are located so that commutation (i.e., reversal of current in the commutated coil) occurs when the coil sides are in the neutral zone, midway between the field poles. The axis of the armature mmf is then in the quadrature axis, whereas the stator mmf acts in the field (or direct) axis. Figure shows schematic representations of a dc machine. The commutator is thus a device for changing the connections between a rotating closed winding and an external circuit at the instants when the individual coil-generated voltages reverse. In a dc machine, then, this arrangement enables a constant and unidirectional output voltage. The armature mmf axis is fixed in space because of the switching action of the commutator (even though the closed armature winding on the rotor is rotating), so the commutator winding becomes pseudostationary.

876_dc machine.png


Related Discussions:- Dc machine

Var compensators employing flexible ac transmission system, Var Compensator...

Var Compensators Employing Flexible AC Transmission System Devices These are a new generation of VAr compensators which employ solid-state devices (thyristors) for the generati

What do you mean by negative impedance converter, Q. What do you mean by Ne...

Q. What do you mean by Negative Impedance Converter? The op-amp circuit of Figure causes a negative resistance R in between the input terminal and ground. In the more general

What is capacitance, What is Capacitance -  Capacitance is explained to...

What is Capacitance -  Capacitance is explained to be the amount of charge Q stored in among the two plates for a potential difference or voltage V existing across the plates.

DC. motors, what''s the difference between DC. motors and AC. motors

what''s the difference between DC. motors and AC. motors

Explain the working of frequency division, Explain the Working of Frequency...

Explain the Working of Frequency Division? A frequency divider able to be constructed from J-K flip-flops by taking the output of one cell to the clock input of the next and th

Define the dma controller interface, Define the DMA controller interface. ...

Define the DMA controller interface. A DMA controller interfaces along with a few peripherals which may request DMA. The controller chooses the priority of simultaneous DMA req

Break over voltage of finger voltage - thyristor , Break over  voltage of...

Break over  voltage of Finger Voltage   The  minimum  forward voltage  when the gate  is opened  at which SCR  starts  conducting  heavily is called  the break over  voltage. To

Newtons law of gravitation, Particles of mass M and m separated in space by...

Particles of mass M and m separated in space by a distance R exert a mutually attractive gravitational force F on one another given by where G is the universal gravitationa

Testing for continuity-earthing, Testing for Continuity : You may have obs...

Testing for Continuity : You may have observed sometimes that when all the connections in the appliance as well as the plug are made properly the appliance may still not work. Thi

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