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Generators & Electric Motors General Discussion

Adding AVR to Capacitor Alternator?


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  #1  
Old 10-20-2018, 02:15:05 PM
cjjmw cjjmw is offline
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Default Adding AVR to Capacitor Alternator?

Hi all,

I'm new to the forum and I'm hoping someone can help me with a project I'm working on.


Is it possible to add an AVR to a cheaper 10kw 240V (120X2) capacitor excited brushless alternator?

All I see on the schematic is two film caps on the main assembly and two diodes and two varistors on the rotor.


Am I right in thinking those varistors are what's doing the actual regulating?
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Old 10-20-2018, 02:52:02 PM
Thaumaturge Thaumaturge is offline
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Default Re: Adding AVR to capacitor alternator?

Won't work. Non brush type generators use harmonic excitement of field. Made to work within a small range of output Hz, either 50 or 60 depending on where marketed. (Meaning designed specifically to run at frequency where sold.)
Might check wikipedia for further information, but bottom line is won't work!
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Old 10-20-2018, 02:59:42 PM
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Default Re: Adding AVR to capacitor alternator?

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Originally Posted by Thaumaturge View Post
Won't work. Non brush type generators use harmonic excitement of field. Made to work within a small range of output Hz, either 50 or 60 depending on where marketed. (Meaning designed specifically to run at frequency where sold.)
Might check wikipedia for further information, but bottom line is won't work!
Doc
That was simple.
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Old 10-20-2018, 03:50:44 PM
Thaumaturge Thaumaturge is offline
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Default Re: Adding AVR to capacitor alternator?

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Originally Posted by cjjmw View Post
That was simple.
Sadly yes. I have a number of small generator heads I would love retasking to run at lower RPM to feed an inverter design. It was investigating such that I learned myself just how difficult it would be.
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Old 10-20-2018, 04:36:34 PM
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Default Re: Adding AVR to capacitor alternator?

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Originally Posted by Thaumaturge View Post
Sadly yes. I have a number of small generator heads I would love retasking to run at lower RPM to feed an inverter design. It was investigating such that I learned myself just how difficult it would be.
Doc

Just how bad are these at regulating assuming no huge load changes?

I noticed Briggs and Stratton claims it'll run a 3 ton air conditioner. Sounds like a bad idea to me for anything else running at the time.
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Old 10-20-2018, 08:00:05 PM
Newoldstock Newoldstock is offline
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Default Re: Adding AVR to Capacitor Alternator?

Not that bad.

The idea is as the load increases the harmonics generated in machine increase and this is what induces the current in the rotor.
The caps resonate at the right frequency, diodes convert AC to DC and supply the field.

No complicated and not the best regulation but they hold well enough to do what most people need.
Not so good for electronics

The varistors are important.
They trim off and spikes and peaks induced from switching and sudden changes.
Without them the diodes may fail and your output AC might get some noise and spikes too
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Old 10-21-2018, 10:24:54 AM
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Default Re: Adding AVR to capacitor alternator?

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Originally Posted by Thaumaturge View Post
...Non brush type generators use harmonic excitement of field...
Huh.

I'm sort of familiar with the 'capacitor-regulated' generator the OP describes (more here: http://www.freepatentsonline.com/4786853.pdf and here: https://patentimages.storage.googlea.../US4296368.pdf)

And I'm sort of familiar with some of the Chinese generators that have a 'harmonic winding', but they have brushes.

So, can you provide any link to a reference that says more about 'harmonic excitement' in a brushless generator?

Last edited by Jim McIntyre; 10-21-2018 at 11:00:38 AM.
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Old 10-21-2018, 11:07:35 AM
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Default Re: Adding AVR to Capacitor Alternator?

there are brush-less systems traditionally regulated.
these have a primary alternator with a stationary field, and rotating rectification of the field current for the main alternator.

this is very much different than the cap regulation.
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Old 10-21-2018, 11:15:10 AM
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Default Re: Adding AVR to Capacitor Alternator?

^ Yes, well aware of that.

I'm curious about thaumatuge's brushless, harmonic-excited machine...
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Old 10-21-2018, 04:21:21 PM
Wayne 440 Wayne 440 is offline
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Default Re: Adding AVR to Capacitor Alternator?

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Originally Posted by Jim McIntyre View Post
...I'm curious about thaumatuge's brushless, harmonic-excited machine...
As am I...
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