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

Explain the construction of a mosfet, Explain the construction of a MOSFET....

Explain the construction of a MOSFET. Draw the symbols and diagrams of both P-channel and N-channel MOSFET. As JFET and MOSFET also have source, drain and gate. Its gate is ins

Determine voltage on the self-biased n-channel, Measurements made on the se...

Measurements made on the self-biased n-channel JFET shown in Figure are V GS =-1 V, I D = 4 mA; V GS =-0.5V, I D = 6.25 mA; and V DD = 15 V. (a) Determine V P and I DSS .

Accidents, what are accidents in an organisation

what are accidents in an organisation

Determine the bandwidth required for transmission, 1. A PCM system uses 8 b...

1. A PCM system uses 8 bits per sample and the analog signal is limited to 4.3 kHz. The PCM data is transmitted using (a) BFSK and (b) ASK. Determine the bandwidth required for tra

Difference between div and idiv instructions, Mention how do the DIV & I...

Mention how do the DIV & IDIV instructions differ in their functionality DIV: Unsigned numbers division and IDIV: Signed number division.

Mode 1 - buck converter , Mode 1 ( 0 By  applying a positive  output ...

Mode 1 ( 0 By  applying a positive  output  pulse  of the pulse  width modulator to  the  transistor Q 1 it gets turned on.  An input  current  in flows  through V in   Q 1

D.c.machines, can voltage regulation be negative?why?

can voltage regulation be negative?why?

Determine the transfer function and driving-point impedance, Q. A filter is...

Q. A filter is a network employed to select one range of frequencies while rejecting all other frequencies. A basic building block often used in integrated-circuit filters is shown

Determine the atomic weight of an atom, Atomic weight of an atom is (A...

Atomic weight of an atom is (A) Sum of the number of protons and neutrons. (B) Sum of the number of protons and electrons. (C) Sum of the number of electrons and n

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