Electromagnetic torque , Electrical Engineering

Electromagnetic torque 

The torque is given by the force on the armature winding multiplied by its radius. Force on a conductor in magnetic field B is: 


so, T=B.I.L.R

The torque opposes the mechanical rotation of the rotor and so the mechanical torque turning the generator must do work against the electromagnetic torque in order to generate the voltage (and current) supplied to the electrical load connected to the generator. Therefore energy conversion occurs from mechanical energy to electrical energy.The flux density B webers/m  can be expressed in terms of the flux per pole, φ,  to give a relation between the electromagnetic torque to be overcome and current produced.


C=machine constant

The equivalent circuit representation of an electrical generator is:



478_Electromagnetic torque.png


The generator itself provides the source tosupply the field current I . Residualmagnetism will provide a small generatedcurrent at first that then builds up as thefield current grows, producing moregenerated current, etc. [NB leaving analternator open circuit will cause thevoltage to build up to the point wherediodes used to rectify the output voltagecan be damaged. Never operate an alternator without an electrical load connected. The output voltage is slightly less than the generated voltage due to the volt drop across the armature winding resistance when current flows. The arrangement of connecting the field winding in parallel with the armature is known as a shunt connected machine. The alternative is to connect the field winding in series with the armature, in which case it as known as a series connected machine.

Reversibility principle of electric machines

An electric machine can be operated as a generator or motor depending on the operation conditions. This is known as the reversibility principle of electric machines. For example, if the generator above is supplied from an electrical source, it will operate as a motor



Posted Date: 8/23/2012 12:40:40 AM | Location : United States

Related Discussions:- Electromagnetic torque , Assignment Help, Ask Question on Electromagnetic torque , Get Answer, Expert's Help, Electromagnetic torque Discussions

Write discussion on Electromagnetic torque
Your posts are moderated
Related Questions
Q. A two-pole rotating machine with a singly excited magnetic field system as its stator and a rotor (that carries no coil) has a stator-coil inductance that can be approximated by

Q. What is the advantage of using JFET as an amplifier? As an amplifier of small time-varying signals, the JFET has a number of valuable assets. First of all it has a very high

Q. Briefly explain about Phasor Method? For sinusoidal excitations of the same frequency, the forced or steady-state responses are better found by the technique known as the ph

Fourier transform  (filtering) (i) Perform low pass filtering in the frequency domain. Write and m-file lowfft.m which does this operation. lowfft.m function lowfft im

Machine Language ( First Generation Language) As we have  already discussed that all digital  circuits  can identify  only two  states which  can be specified  by 0 and i henc

what is ohm?

Q. Athree-phase, 60-Hz transmission line has a total series impedance of 22.86 62.3°  per phase. It delivers 2.5 MW at 13.8 kV to a load connected to its receiving end. Compute th

Q. Several forms of interference? Interference may take several forms: ac hum, higher frequency pulses and "whistles," or erratic waveforms commonly known as static. Interferin

how magnetic field is related to electric field

Q. What do you mean by Load factor? The two components of electric service are demand and energy. Demand is the maximum level of real power which the electric utility must supp