Brushless AC Generator?

There are tons of articles and peer reviewed papers- use the terms "brushless AC [generator] exciter" in your search. You'll get all the mathematics and FEA analysis summaries anyone could hope for.

Thanks Fred.

Using exciter instead of generator did give me a new list of things to look at..... still mostly motor-generator manufacturers though. It did produce one paper that looks as though it could be interesting, (when I have installed Ghostscript/Ghostview in order to read .ps files).

The brushless AC generator arrangement I have seen consists of a standard design generator (same math model as in any good AC machines book) with the DC field provided by a small inside-out generator, stationary field windings powered by the voltage regulator and rotating 3-phase output windings identical in function to regular stator windings, the output of which is rectified and supplied to the main machine field windings. So the exciter is again the same math model as a standard AC generator, same as the main generator with different parameter values. Your situation may be different, but I think you will be able to find separate models for the exciter and generator and combine them for any practical arrangement.

I ran into several IEEE and IOP articles on the rotating rectifier analysis.

I might be blowing smoke up my own shpiel here, but if you're looking for info on an AC generator, you might try "alternator" - somebody _must_ know something about them: they've been using them in cars for decades. :-)

Cheers! Rich

What happens when you rename it *.PDF or drag & drop it onto Acrobat? (I already have GhostScript installed and haven't bothered with Adobe for a while.)

I tried it ,neither course works,adobe complains onknown or damaged.

Tony Williams wrote in news: snipped-for-privacy@ledelec.demon.co.uk:

Hi Tony, Here's another free postscript reader for level 1 that might be of interest. Instead of the multi megabytes needed for Ghostscript, the Rops installation is only 549K:

The free version of Rops has a very short delay on loading but it is not annoying.

After loading Rops for PS and Foxit for PDF, I was finally able to erase Ghostscript and all the later versions of Adobe Acrobat. I kept Acrobat 5 for rare occasions when the smooth text function is needed to improve readability. All these programs load instantly on my 450MHz AMD machine.

The free Foxit reader is at

Regards,

Mike Monett

Yes that's the type, invented about 50 years ago afaik. Also known as the 2-stage aircraft generator.

I hadn't thought of simply cascading two generators, one loading the other. BTW I have been told that a simplified transfer function has two roll-off's, at about 10Hz and 30Hz in a typical 50-100KVA generator, varying slightly with loading.

Thanks,

Downloaded, installed, works ok. Thanks Mike.

I just found some notes from a course in control of generating systems given by Basler Electric at a 1991 Power Control and Protection conference, which claims that this is the most common design. These notes cover essentially everything a systems engineer needs to spec a generator control system for a particular situation. The only info you need for that purpose is an understanding of the application requirements and the generator specs (primarily the saturation curves); the regulator is normally tuned for fastest stable response to a step change in load with the usual tuning procedure for PID controllers, without any attempt to model the dynamic response of the system. Presumably you want to go beyond this, perhaps to design a higher order controller.

That seems reasonable, perhaps the first roll-off is due to the main machine and the second due to the exciter.

The type of model you need depends on what you want to do with it. It takes a lot more model to design a generator than to design a voltage regulator for it, for instance, and something in-between to evaluate the effect of exciter ripple on generator output.

I have heard that the AC Machines professor at Drexel University, which had (has?) a pretty good power program, still used (at least up to mid 90's) "Principles of Alternating Current Machinery" 4th edition, 1953, by Lawrence and Richards (who first developed much of modern AC machine theory at MIT), because nothing written since is as good. Last time I checked used copies were readily available fairly cheap.

The other way round, see below. :)

I am looking at the design of a circuit (analogue in the first instance) that emulates a 2-stage generator. This can be used to close the loop around the voltage regulator without actually connecting it to a real generator (and an expensive drive). This is standard practice in the testing of voltage regulators and I have done it several times before, but would like a more solid mathematical basis for the next design.

Useful pointer, will investigate further, thanks.

You're welcome, Tony. As long as we are on this downloading software kick, here's two more that I find absolutely fantastic. One is an email client that handles an unlimited number of email addresses so you can have a unique address for every need. The program is Geminisoft Pimmy. Version

Unfortunately, the free version of Pimmy doesn't handle binary attachments, which are so necessary for this newsgroup.

But another free newsreader does a terrific job on binaries. This is by far the best newsreader I've come across, especially if you like working from the keyboard. It is blazingly fast, and very easy to go back through previous posts to find one to append to, like I had to do with this one. It is called XNews, and is available here:

The manual is kind of skimpy and misses some features in the software. But it is fairly easy to figure out what the commands do once you know how the author thinks.

His program literally makes newsgroups a pleasure! Highly recommended. Regards,

Mike Monett

I couldn't find an easily obtainable 4th edition, and anything earlier than 1953 may not know about the brushless exciter. I did find and have ordered the book below.

The Electric Generators Handbook. Ion Boldea. CRS Press Inc, US. ISBN: 084931481X. GBP99 from amazon.co.uk.

It's a 2-volume set, the first vol deals with the older synchronous (fixed speed) generators and the second vol deals with variable frequency machines, including a chapter on aircraft generators.

At that price I do hope there's some decent information in there..... just have to wait and see.