electricity generation

[rattus]

Don't think so:

Don't think so:

So basically the generator doesn't even need to spin once the capacitor is charged.... the inductance of the windings and the capacitance will be a tank circuit which circulates the energy?

You might have a tank circuit, but the resonant frequency would almost certainly not be 60Hz. I prefer to believe that the mass of the spinning rotor provides the energy to charge the capacitor through a quarter cycle. Then the cap discharge would provide mechanical energy to the rotor for the next quarter cycle, etc., etc.,

BTW, in analog computers, the analog of mass is inductance.

 

[coulter]

Isn't there an adjustement on the exciter current or voltage that changes the amount of VARs that the generator can (will) supply?
Don

As with most things electrical, it depends.

Coulter' Law of Generators (limited to standard 3ph alternators):

Every generator in the world has the same two knobs.
1. The voltage regulator controls the DC current to the rotating field.
2. The throttle controls the power input to the gen shaft

What these knobs do is dependent on if the generator is running in parallel or islanded.

Island:
The field current controls the voltage and throttle controls the frequency . The load is what it is (Really, Carl:roll: ). The gen can't change the pf or the resistance. Inductive loads (lagging pf) take vars. Inductive loads will pull the gen voltage down. The voltage regulator responds by increasing the field current to pick the voltage up. Capacitive loads (leading pf) pump vars back to the system. Capacitive loads will push the voltage up. The VR decreases the field current to pull the voltage back down.

Increases in the load (real power) will pull the frequency down (gen slows down). The governor increases the throttle to pick up the frequency.

Parallel Operation:
The gen has the same two knobs, but they really react differently.

When paralleled, the frequency and voltage are stuck. The other generators will hold freq and voltage. Once your gen is synced and on line, it can not vary the voltage nor frequency.

The field current controls var sharing and the throttle controls kw sharing. Increasing the field current causes the gen to put out more vars. The gen pf meter will go lagging. More vars can't go into the load (it is what it is), so the other generators will respond respond by reducing their field drive and suck vars.

Increasing the throttle causes the gen to pick up more power. The kw meter will increase. The other generators respond by backing down their throttle and put out less power.

I know this sounds simplistic, but the physics are real close to actual generator action.

carl

 

[coulter]

...BTW, in analog computers, the analog of mass is inductance.

Rattus -
Serious question: What is the analog of capacitance?

carl

 

[LarryFine]

Rattus -
Serious question: What is the analog of capacitance?

A vacuum?

Or perhaps velocity?

 

[rattus]

Rattus -
Serious question: What is the analog of capacitance?

carl

A spring. Electrical waveforms simulate the motion of mechanical systems. The math for either is the same.

One fellow designed a calculator utilizing analog circuitry. It didn't fly.

 

[e57]

It is not the generator shaft that gives and receives energy. It is the generator windings. Energy is stored in the windings, in the form of a magnetic field. The intensity of that field goes up and down in a sinusoidal pattern. At the same time, energy that is stored in the capacitor (in the form of an electric field) is going down and up in a sinusoidal pattern. If there are no losses, there will be no need to replace those losses by adding mechanical power to the shaft.

I've been day dreaming about that since the fifth grade! (Intro to science as a kid) Later getting into the trade, learning how voltage regulation works on diesel generators with stator windings I learned where all those losses went. Into conquering momentum electrical and mechanical...

When paralleled, the frequency and voltage are stuck. The other generators will hold freq and voltage. Once your gen is synced and on line, it can not vary the voltage nor frequency.

The field current controls var sharing and the throttle controls kw sharing. Increasing the field current causes the gen to put out more vars. The gen pf meter will go lagging. More vars can't go into the load (it is what it is), so the other generators will respond respond by reducing their field drive and suck vars.

Increasing the throttle causes the gen to pick up more power. The kw meter will increase. The other generators respond by backing down their throttle and put out less power.

I know this sounds simplistic, but the physics are real close to actual generator action.

True, varying the voltage output (Electrical) or throttle (mechanical) on one will take them out of real parallel operation moving the load to one, and I'll add, eventually make one the load for the other. I used to do this with generators as a load bank against each other. But the other generators will only back down the throttle if equiped to do so - lacking that precise fuel control you could load equal sized generators to capacity of only one, and one carrying the total load. Not so much that the other generator is acting as a motor - depending on the design it wound not be able to - but more of a big electro-mecanical brake. Using the windings as a linkage between both engines. The measurable output fequency and voltage will be the one with the higher voltage actually being produced, and or the one with the higher frequency. The other is dead wieght to some degree.:wink:
(FYI kids - don't try that at home - unless your gennie can take such abuse... )

 

[crossman]

I prefer to believe that the mass of the spinning rotor provides the energy to charge the capacitor through a quarter cycle. Then the cap discharge would provide mechanical energy to the rotor for the next quarter cycle, etc., etc.,

That is what I was thinking also.