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Messages - CS6_owner

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Generators / Re: Capacitor calculation for DIY stand alone genset
« on: May 05, 2021, 08:35:08 PM »
Hats off to CS6-owner for a well said post. Pretty much laid it out. Looks like a single phase motor would, for simplicity’s sake, be a better way to go.

What about a three phase generator, can you run a load off one coil with say a star winding?

All I said above is for a 3 phase motor/generator.



If you want to feed a heavy mono phase load, you can use (with a synchrone 3 phase generator) a "dog leg delta". This is used to make sure the generator is balanced. Never use just 1 coil to feed a mono phase load. See: http://server.idemdito.org/techtalk/elec/stroomgroep/monofasig.htm (in dutch)

Apparently you can use a mono phase asynchronous motor as generator. See: http://server.idemdito.org/techtalk/elec/stroomgroep/asynchroon.htm (in dutch)

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Generators / Re: Capacitor calculation for DIY stand alone genset
« on: May 03, 2021, 04:26:17 PM »
You have a motor with 400V coils.

This means that in delta, grid voltage needs to be 400 volts. This is the "normal" grid voltage in a modern factory.

If you have a 690V grid, you would need to configure the motor in star (is not used).

This is a normal configuration for "new" motors. You can thus use a star/delta configuration to limit the startup currents on a 400V grid.

Asynchronos motor are ideal to use as generator while grid connected. Sadly, this is illegal (for safety reason) in most parts of the world.

It could be used not grid connected (delta configuration), if you have a constant load (in star configuration with 230V loads), like an electrical heater. This electrical heater could be a star configuration of eg 3 1 kW heaters.

Using this motor as generator, you NEED a balanced load across the 3 coils. The way an unbalance would be solved is here not available (the neuter line in the center of the star is used to solve the unbalanced loads). If you would use the motor as generator with a not balanced load (eg 1Kw, 2kW and 3 Kw heater) not grid connected, you would get eg 180V on 1 heater (not a big problem) 260V on another and maybe 290 V on the third (big problem).

If you would have 3 400V heaters, then you could put both generator and load in star configuration. You could then connect both centers of the star with a neuter line, and thus use an unbalanced load. This would give other problems, mainly overheating of the coil that has the largest load and cogging. Not advised, and also not so easy to get 400V monofase heaters.

Using an asynchrone motor as a grid tied generator, you don't need the capacitors. The grid supplies the needed reactive power. And the load is almost always balanced.
Using it standalone, you do need the capacitors. And when you change the load, you need to change the value of the capactor or the voltage and frequency would drift.

Some reading:
http://www.gohz.com/induction-generator-synchronization-with-grid#:~:text=The%20grid%20feeding%20powering%20the,will%20deliver%20power%20in%20sync.
https://www.qsl.net/ns8o/Induction_Generator.html
https://www.smokstak.com/forum/threads/induction-generator-from-synchronous-generator.20046/#post-89860
https://www.smokstak.com/forum/threads/motor-starter-for-induction-generation.161917/
https://www.survivalistboards.com/threads/homemade-induction-generator.24036/
https://www.mytractorforum.com/threads/induction-generator.91257/
http://users.telenet.be/b0y/

PS: Do this on your own risk. I'm not responsable if you get killed...

 

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