Equation relating rotational velocity and output electrical power

AI Thread Summary
The discussion focuses on the relationship between angular velocity, output electrical power, voltage, and frequency in alternators and DC generators. It begins with Maxwell's equation, leading to Faraday's Law, which describes how induced voltage in a loop is related to the changing magnetic field. For a rotating loop in a magnetic field, the root mean square (rms) output voltage can be calculated using the formula V = (ωNA₀B₀)/√2. The efficiency of alternators varies significantly, with automotive models averaging around 50-60% efficiency, while utility-scale alternators can reach up to 99% efficiency. Understanding these principles is crucial for optimizing electrical power generation from mechanical sources.
Charles123
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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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Start with Maxwell's equation in differential form
curl\space E = - dB/dt
Integrate to get Faraday's Law:
\oint E\space d\ell= - \frac{d}{dt}\int_{A}^{}B\cdot n \space dA
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
V= \frac{\omega NA_0 B_0}{\surd 2}

Bob S
 
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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.
 
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