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

Calculate voltage and frequency, The stator and rotor of a three-phase, 440...

The stator and rotor of a three-phase, 440-V, 15-hp, 60-Hz, eight-pole, wound-rotor induction motor are both connected in wye and have the following parameters per phase: R1 = 0.5

Control systems, why open loop system is stable and why degree of stability...

why open loop system is stable and why degree of stability varies in closed loop system

Illustrate output-rate control, Q. Illustrate Output-rate control? A sy...

Q. Illustrate Output-rate control? A system is said to have output-rate damping when the generation of the output quantity in some way ismade to depend upon the rate atwhich th

Compare in-channel signalling with common channel signalling, Q. Compare in...

Q. Compare in-channel signalling with common channel signalling? Network wide signalling also involves end to end signalling between originating exchange and the terminating ex

Human resources - kpi, Human Resources - KPI It is the responsibility ...

Human Resources - KPI It is the responsibility of management to have the lean, capable, customer friendly organization that strives for catering to diversified need of all the

CST162_hw5, Draw the state diagram for the state machine described by Table...

Draw the state diagram for the state machine described by Table 7.5 in the text. Note, the table shows the transition to the next state S* from the current state S for the next set

Functions of the physical layer in the internet model, (a) Describe the f...

(a) Describe the four functions of the physical layer in the Internet Model. (b) (i) With the help of a diagram describe the main stages involved in the digitization of a

Explain the meaning of ring counters, Explain the meaning of Ring Counters?...

Explain the meaning of Ring Counters? A ring counter is fundamentally a circulating shift register in which the output of the most significant stage is fed back to the input of

What is open-loop voltage gain, Q. What is Open-loop voltage gain? The ...

Q. What is Open-loop voltage gain? The op amp amplifies the difference vd between the voltage on the noninverting (+) terminal and the inverting (-) terminal; see Figure. The t

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