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

List the uses of usart, List the uses of USART. USART- Universal Synch...

List the uses of USART. USART- Universal Synchronous Asynchronous Receiver-Transmitters. It is used to transmit and receive the data in serial communication mode. It is

Dc machince, what ''s part of dcmotor or dc generator

what ''s part of dcmotor or dc generator

Digital electronics, Digital Electronics: We have study the fundamenta...

Digital Electronics: We have study the fundamentals of Digital circuits. Primary we have studied the mathematics of Binary numbers also called as Boolean algebra and how to im

Determine the peak fundamental component of the mmf, Q. A two-pole, three-p...

Q. A two-pole, three-phase synchronous generator has a balanced three-phase winding with 15 turns per phase. If the three-phase currents are given by i a = 100 cos 377t, i b =

Discuss the low- and high-frequency designs, Consider a CS JFET amplifier w...

Consider a CS JFET amplifier with the following parameters : R 1 = 350 k; R 2 = 100 k, R SS = 1200 , R D = 900 , R L = 1000 , R S = 2000 , ro = 15 k,gm = 6 × 10 -3 S,

Dual trace and dual beam cro, what is difference between dual trace and dua...

what is difference between dual trace and dual beam cro?

Lki load register pair immediate instruction , LKI  Load Register pair  ...

LKI  Load Register pair  Immediate  Instruction This instruction is used to copy or  load  16 bit  data specified  in the  instruction  directly into  the register pair. The i

Dtl and ttl logic circuits, Q. DTL AND TTL LOGIC CIRCUITs? Bipolar tran...

Q. DTL AND TTL LOGIC CIRCUITs? Bipolar transistorswere the first solid-state switching devices commonly used to implement digital logic circuits in the 1950s and 1960s. These c

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