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

What are the flags used in 8086, In 8086 Carry flag, Parity flag, Auxiliar...

In 8086 Carry flag, Parity flag, Auxiliary carry flag, Zero flag, Overflow flag, Trace flag, Direction flag Interrupt flag and Sign flag.   Mainly there ae two types of int

Energy stored in the coil, The term representing the energy stored in the c...

The term representing the energy stored in the coil may be written in terms of the inductance of the coil as... The energy stored in the coil increases with the square of t

Explain the chemical properties of insulating materials, Explain the chemic...

Explain the chemical properties of insulating materials. Chemical properties - Chemical resistance: Presence of gases, acids, water, alkalies and salts influences different

Digital electronics, Design a 4-bit synchronous counter that has the follow...

Design a 4-bit synchronous counter that has the following sequence: 0 ?4? 9?12 ? 14 ?15 and repeat using: i) JK FF ii)D FF

Describe the working of binary comparator, Digital Systems 1. Describe ...

Digital Systems 1. Describe the working of Binary comparator (Magnitude comparator) a. Define Binary comparator b. Binary comparator working process with logical diagrams 2.

Electronics, Figure 1(a) shows a simple one-stage MOSFET amplifier. The inp...

Figure 1(a) shows a simple one-stage MOSFET amplifier. The input-output relationship is graphed in Figure 1(b), where the solid curve indicates operation in the saturated region an

Determine the i-v characteristic of the network, Determine the i-v characte...

Determine the i-v characteristic of the network shown in Figure by the use of breakpoint analysis.

Illustrate the construction and working of thermistor, Illustrate the const...

Illustrate the construction and working of:- (i) Pressure Thermometer (ii) Selective Radiation Pyrometer (iii) Thermistor (iv) Laws of Thermocouple

Carry flag - registers, Carry Fla Registers  The  size  of the accumul...

Carry Fla Registers  The  size  of the accumulator is of 8 bit  if after  any arithmetical  or logical  operation 9 th   bit is generated i e  there is  carry beyond  D 7   bi

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