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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
Cm =machine constant
The equivalent circuit representation of an electrical generator is:
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 machinesAn 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
(a) Show the equivalent NOR realizations of the basic NOT, OR, and AND gates. (b) Show the equivalent NAND realization of the basic NOT, AND, and OR gates.
1. Sum of forces is zero velocity remains constant.[If the particle is initially at rest, it will remain at rest for as long as the sum of the forces is zero]. 2. Sum F of for
controller
If a permanent magnet creates the flux in a magnetic circuit, the flux exists without the need for a coil, so how does Amperes Law apply to this case? In this case the flux is
Q. What is a heat sink? List the factors, which determine its efficiency. To reduce the chance of thermal runaway, the rise of temperature at the collector junction to a danger
what are the different digital modulation techniques?
draw a graph of V=IR for R=300ohms over the domain -3mA
Describe the nature of electricity
What is RXD? RXD- Receive Data Input This input pin of 8251A gets a composite stream of the data to be received by 8251A.
discussion for experiment
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