Equation relating rotational velocity and output electrical power

In summary, the equations that relate the angular velocity of an alternator rotor with its output electrical power, voltage, and frequency are Maxwell's equation and Faraday's Law. The induced voltage in an N-turn loop around the perimeter of an area A is equal to the time derivative of the perpendicular magnetic field integrated over the area inside the loop. The efficiency of an alternator can vary greatly depending on its speed and load, with car alternators typically having an efficiency of 50-60% and utility central station alternators having a much higher efficiency of 99%.
  • #1
Charles123
132
0
What is the equation that relates the angular velocity of an alternator rotor with its output electrical power, voltage and frequency (not necessarily just one equation) .
And for a DC generator?
I know that when you calculate the power generated by a turbine you multiply its efficiency of conversion and the theoretical power that you can extract from a flow with that swept area by the turbine. I assume that in that efficiency is the factor of conversion to electrical power. How does that work?
regards
 
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  • #2
Start with Maxwell's equation in differential form
[tex] curl\space E = - dB/dt [/tex]
Integrate to get Faraday's Law:
[tex] \oint E\space d\ell= - \frac{d}{dt}\int_{A}^{}B\cdot n \space dA [/tex]
The induced voltage in an N-turn loop around the perimeter of an area A is equal to minus the time derivative of the perpendicular magnetic field integrated over the area inside the loop. Either the magnetic field or the area can be a function of time. If an N-turn loop of area A(t) = Aosin(ωt) rotates in a dc magnetic field B0 with angular frequency ω, then the rms output voltage is
[tex] V= \frac{\omega NA_0 B_0}{\surd 2}[/tex]

Bob S
 
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  • #3
That's a kinda general question...
like asking what make a centrifugal pump work..

Here's a fairly scholarly article on automobile alternators and where they are going
www.rle.mit.edu/per/JournalPapers/JPtpemay04p618.pdf

and the Wikipedia page really is pretty good
http://en.wikipedia.org/wiki/Alternator

Alternators in cars have widely varying efficiency at various speeds and loads. Take 50-60% as ballpark.
Utility central station alternators can be, as you doubtless know, 99% efficient.
 

Related to Equation relating rotational velocity and output electrical power

1. How can rotational velocity affect the output electrical power?

Rotational velocity is directly proportional to the output electrical power in a system. This means that as the rotational velocity increases, the output electrical power also increases.

2. What is the equation that relates rotational velocity and output electrical power?

The equation is P = ω * τ, where P is the output electrical power, ω is the rotational velocity, and τ is the torque.

3. Can the equation relating rotational velocity and output electrical power be applied to all systems?

Yes, this equation can be applied to any system that involves rotational motion and output electrical power, such as motors, generators, and turbines.

4. Is there a limit to how much output electrical power can be achieved by increasing the rotational velocity?

Yes, there is a limit known as the critical speed. Beyond this speed, the system may become unstable and the output electrical power may decrease instead of increasing.

5. How does the output electrical power change if the rotational velocity is kept constant but the torque is increased?

The output electrical power will also increase as the torque increases, following the same equation P = ω * τ. However, the rate of increase may not be as significant as when the rotational velocity is increased.

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