How would one go around simulating a generator in LTSpice? Its output waveform would be sinusoidal.

Say, I'd like to sim the fact that as the revs go up, so does the power generated, it's voltage and its frequency. And when it stops, it'd behave like a short circuit.

The generator type would be variable reluctance.

 

as the revs go up, so does the power generated, it's voltage and its frequency.

Would you like the frequency and voltage to change with time?

The generator type would be variable reluctance.

How does that affect the simulation?

 

Would you like the frequency and voltage to change with time?

Yes

How does that affect the simulation?

I don't know ... but I know that a variable reluctance generator is brushless, so if the generator stops, then its winding would behave like one big inductor ... perhaps it's inconsequential, because in my circuit the generator's output would go through a rectifier before being connected to the rest of the circuit. And current cannot back-flow through a full bridge rectifier.

 

I can see that LTSpice's voltage source element has a parameter for the equivalent series resistance, but not for inductance, which a generator most definitely has. How is this supposed to be modeled? By placing an inductor connected in series with the voltage source?

 

Load resistance step changes produce generator current step changes, without inductive transition processes.
Do not take it in account.

 

I can see that LTSpice's voltage source element has a parameter for the equivalent series resistance, but not for inductance, which a generator most definitely has. How is this supposed to be modeled? By placing an inductor connected in series with the voltage source?

Yes.

For the time varying frequency and amplitude, use the behavioral voltage source B1, as shown below.
The time*time function changes the frequency as the square of the time, and the third time function changes the amplitude.
You just adjust the variables to get the change in amplitude and frequency with time that you want

 

Yes.

For the time varying frequency and amplitude, use the behavioral voltage source B1, as shown below.
The time*time function changes the frequency as the square of the time, and the third time function changes the amplitude.
You just adjust the variables to get the change in amplitude and frequency with time that you want

View attachment 154547

Beautiful equation ... I didn't know that LTSpice had that capability, nor how to use it. I assume that the same concept can be applied to other components, such as resistors? That feature's gonna come in handy in the near future.

Thank you very much!

 

I assume that the same concept can be applied to other components, such as resistors?

Sure.
LTspice has a lot of capabilities that many who use it don't know about.

Below is the simulation with a varying R1 load resistor with time.
Notice the plot of the the output resistance with time, [V(out)/I(R1)].

 

Sure.
LTspice has a lot of capabilities that many who use it don't know about.

Below is the simulation with a varying R1 load resistor with time.
Notice the plot of the the output resistance with time, [V(out)/I(R1)].

View attachment 154551

What about time-conditional statements?
Something like: If time<=0.1 then R=100 else R=1000

How would you go about that?

 

What about time-conditional statements?
Something like: If time<=0.1 then R=100 else R=1000

How would you go about that?

There might be a better way, but I would use a voltage controlled switch (SW) to switch a component in/out at the desired time.

Edit: Below is a simulation for your example problem.

 

"If time<=0.1 then R=100 else R=1000" becomes R=if(time<0.1,100,1000) in LTspice-speak.
And here's another way of simulating a generator, using the Modulate device.

 

I found this extremely useful link containing LTSpice manuals, examples and tutorials. It even shows how to model a transformer! ... I've already downloaded all the PDF's and put them in my Kindle to-read list.

 

Question ... is there a way of estimating a DC generator's output, based on its RPM's, magnets size, number of coils, number of turns, and wire gauge? I've already measured the coil's impedance and inductance, if that information is important.

 

Question ... is there a way of estimating a DC generator's output, based on its RPM's, magnets size, number of coils, number of turns, and wire gauge? I've already measured the coil's impedance and inductance, if that information is important.

You can try to use Vizimag.

Example: http://vixra.org/pdf/1511.0252v3.pdf

 

You can try to use Vizimag.

Example: http://vixra.org/pdf/1511.0252v3.pdf

Very interesting program ... but really hard to understand. Also, it seems that the people that created it have gone out of business. The www.vizimag.com website is a graveyard.

 

Very interesting program ... but really hard to understand. Also, it seems that the people that created it have gone out of business. The www.vizimag.com website is a graveyard.

Why not use recommendations in post #108 ?
Secure iron disk on motor spindle, glue 8 magnets on disk and play with coil, gap, magnets number and distance between magnets.
When you found optimal (by voltage) parameters, you can easily recalculate them.
Voltage is directly proportional to number of magnets (coils), number of coil turns and RPM.
By this way you can select equal magnets, because they may have different magnetic parameters.

 

I've just downloaded and installed MaxFEM, and I'm gonna start learning it.

 

I've just downloaded and installed MaxFEM, and I'm gonna start learning it.

Oh thanks C, now I have to learn both MaxFem and Spanish.

 

ViziMag. Magnets: D=10, H=5, gap=2, 4, 6.
Registration.

 

ViziMag. Magnets: D=10, H=5, gap=2, 4, 6.
Registration.
View attachment 154864

Can you share the file of this sim? ... I'd like to play with it a bit, if you don't mind.