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: 

F=B.I.L

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.

T=Cm.Ø.Ia

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
circuit diagram of 2 bit magnitude comparator

The resistance of 1.5 km of wire of cross-sectional area 0.17 mm 2 is 150Ω. Determine the resistivity of the wire.

Q. Advantages and Disadvantages of rc coupled amplifier? Advantages 1. Aids excellent frequency response.The gain is constant over the audio frequency range 2. It has l

Explain factors that change the resistivity of conducting materials. Temperature- Electrical resistance of most metals rises with increase of temperature whereas those of sem

Structure and use of PNP transistor: The figure opposite is a schematic presentation of a PNP transistor related to two voltage sources. To construct the transistor conduct ap

A three-phase, 4160 V, 60 Hz, 3000 kVA generator supplies the following three phase loads:  A 00 kVA at .7 pf lagging, D 00 kVA at .9 pf lagging, and C 50 kVA at unity pf.

Draw a relay construction diagram and briefly explain the operation of a relay. Define the terms normally open and normally closed. Define the terms Set and Reset for relays.

Q. A 5-kVA, 480:120-V, two-winding, 60-Hz, single-phase transformer has an efficiency of 95% while delivering rated load at rated voltage and 0.8 power factor lagging. This transfo

20 cells with emf 1.45V and internal resistance 0.5Ω for each cells is linked 4 rows which every rows having of 5 cells in series. Load resistance 15Ω is connected to the battery.

reflections, journey about the subject solid mensuration