Generator Waveform Equations

AC? DC? Read Electric Machinery, Fitzgerald and Kingsley, any edition.

Classic Textbook.

3-phase DC generator would be really interesting...

I was thinking the same thing. I thought "phase-to-phase" gave it away.

Thank you for the references. I will look up that title as well as the others suggested. It should be enough to get me started. I'd like to test some devices connected to a waveform generator that models the AC generator output of a 750KW (4160Vac stepped down 20:1 to 208Vac) at .80 PF. I do not know the current draw, but can simulate just about anything, so a common range will work fine.

Cheers,

TR

Read this one:

http://www.dataforth.com/catalog/pdf/an101.pdf

I don't think you can do it without knowing the load characteristics. A generator by itself has it's own characteristic equation, which is a function of several variables, including not only Thevenin equivalent circuits, but also modifications to the ideal linear characteristic impedances.

I have modeled three phase generators and transformer systems using Spice software quite effectively, at least for theoretical analysis. One also has the ability to model the effects of the variability of the actual load on the system, the effects of imbalance, etc.

I agree with "Edbear", " Read Electric Machinery, Fitzgerald and Kingsley, any edition."

You start reading Kron, and get swamped by tensors. Fitz is clear, concise, and has lots of readily comprehended diagrams - an ideal introductory text. ("At the time of his death, Gabriel Kron was arguably the greatest electrical scientist ever produced by the United States.")

Now, a brief (well, brief for me) actual answer. If your 3 phase generator is ideal (and none are, even those with superconducting windings sitting in some lab) - if your generator is ideal, the VOLTAGE waveform will be a pure perfect sinusoid, line to line (120 √3 = 207.85v), or line to neutral (120v for a WYE wound 3 phase generator, which you seem to be discussing.) Power factor, load type or load nonlinearities will not affect the generator's terminal voltage.

But the CURRENT waveform will be severely affected. The effect of nonlinear loads, such as switching power supplies, light dimmers, thyristor or SCR motor speed controllers will be astounding, and the current waveform will not look at all sinusoidal. Moreover, the high third harmonic content of these distorted current waveforms can add up IN PHASE at the neutral (3 x 120° = 360° = in phase), producing an overloaded neutral, producing high heat, producing fires.

In a real generator, the nonlinear winding currents produce internal voltage drops across the generators actual non-zero internal winding impedances. These internal voltage drops produce non-sinusoidal voltages at the generators terminals. And if one of the external loads is a downed power wire intermittently arcing to ground, there will also be plenty of high frequency noise appearing on the generator terminal's output voltage. This is the principle behind "Arc Current" interrupters or circuit breakers now required in branch circuits supplying bedrooms.

My advice to "trmelle" is to spend several years studying, and several years playing with hardware. I tell you, blowing out 100,000 amp interrupting capacity fuses is a real blast, and very educational - teaches you to stay far away when that newly upgraded Bus Duct and its attendant 1,000 amp breaker is first turned on.

Hope this helps a little.

RGC, A Mechanic of New York