"Amplidyne" The wonder generator? 4

[unpluged]

Hello all

Can anyone help me get a grip on what actually happens to make the amplidyne generator only need a small input change to create a large output? Whatsitdo?
If I am understanding it correctly,I believe it has some sort of short circuited wire, and or brushes.

I would appreciate a simple step by step look or explanation of how it can be so powerful.

Thanks for any advice or links.
The simpler the better would be helpful too.

 

[Skogsgurra]

Are amplidynes used these days?

They needed too much care with their collector, sets of brushes, bearings, alignement, lubrication and all such stuff that we hate.

I have an old manual (about the Centurion tank gun system) where the amplidyne is described. But it will be difficult to find. Somewhere in the attic...

The amplidyne is a DC generator with an internal positive feed-back. So you get a high-level output from a weak control signal. That was an advantage back in the forties/fifties when control signals were produced in valve amplifiers and power levels above a few watts were expensive to get.

Amplidynes were later replaced by transductors, thyristors and lately by PWM servos with PM motors. They are history.

This link

http://www.eugeneleeslover.com/USNAVY/CHAPTER-10-D.html

has good information on amplidynes.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[ScottyUK]

There's some discussion of the Amplidyne from about half way down this page. If my memory is right, 'Amplidyne' is a contraction of 'Amplifying Dynamo' which probably gives you some clue as to how it works.

http://www.fieldlines.com/story/2005/5/1/82641/89716

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Sometimes I wake up Grumpy.
Other times I just let her sleep!

 

[oftenlost]

The GE amplidyne, renamed the metadyne and various other names in other countries, is still in limited use today. The diagrams in Gunnar's link show the connection well enough. This little generator had the normal output brushes shorted together through a small resistance. The resulting armature reaction was taken advantage of with a second set of brushes at 90 degrees from the first, fed through a compensating field which balanced out the circuit. I have a shop manual in my files for the GE units. These are temperamental little units which did not tolerate inexpert attention.

 

[unpluged]

Skogsgurra,ScottyUK,and oftenlost

It was a pleasure to receive opinions and links for my question on the amplidyne generator.

Skogsgurra, the link carried a wealth of details for me to review, and yes I believe it must of been a constant upkeep on the systems that seem to be outdated now.

ScottyUK, I am going to go over the posts on your link,I thank you for the link to it.

oftenlost
If you happen to have time to find your old shop manual, I would like to know what you find.
If anyone finds old booklets that they care to share on this, I am always interested.

I am working on a new motor design, and I am trying to get an idea on different designs of motor/gen. designs and function.
Thanks for the help guys.

 

[unpluged]

ScottyUK
Quote;
(If my memory is right, 'Amplidyne' is a contraction of 'Amplifying Dynamo' which probably gives you some clue as to how it works.)

Indeed, it should give me a clue, but can you give me a hint to what (contraction of amplifying dynamo) means?

Sorry to be a bit out of touch with some terminology.

 

[waross]

It has been a few decades since I worked with amplidynes but a rough example from memeory may help explain.
A small amplidyne would have a control signal that varied from zero to 2 watts. The amplidyne output would vary from zero to 1500 watts. The output would power the field of a generator that had the armature direct connected to the armature of a motor. The motor would have the field continuously excited at rated voltage.
In a simple application, a rheostat could be used to generate the control signal and control a motor of about 40 HP from stopped to full speed in either direction.
Small amplidynes such as this were built with a small 3 phase motor on the same shaft in the same frame. Larger models were belt driven.
The units that I was familiar with had a power gain of about 750 to 1.
I understand that for large horsepower installations an excitation generator may be included in a cascade configuration.
That is, an amplidyne controlling an excitation generator which in turn excited the field of a larger generator.
Field forcing may be used to improve response time.
respectfully

 

[ScottyUK]

Re. Contraction of Amplifying Dynamo": the word Amplidyne is derived from Amplifying Dynamo. Guess the 'E' was added to aid pronunciation.

Waross has covered the operating principle, and one of the contributors to the link I posted expanded somewhat on that. At a simple level the small input signal is boosted by the output of the device which is itself dependent on the input signal. The small input is amplified because a fraction of the dynamo output is fed back into a compounding field winding which aids the input winding. The output is picked off by a separate set of brushes to those used in the positive feedback arrangement. I'm no expert on these things - they were being superseded when I was a little kid. I've only worked on one and that was a fascinating relic which I enjoyed working on, part of a generator control system which was old before I was born.


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Sometimes I wake up Grumpy.
Other times I just let her sleep!

 

[starkopete]

A good source for operation theory on "Rotating Amplifiers" (including amplidynes, 2-stage and multi-stage rototrols) would be any of a number of books on DC Machines authored by Michael Liwschitz-Garik. These books are out of print and were published in the '40s & '50s. You can still find them on the inter-net through some of the used book websites.
Of the volumes I have he devotes the most time to the subject (almost 15 pages) in one titled "Electric Machinery, Volume I, Fundamentals And D-C Machines".

 

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starko
quote:
(books on DC Machines authored by Michael Liwschitz-Garik)

such help!


Now that I have all this to work with, I am so exhausted from my 12 hr day at work, that I do not think I can even get to it, but I will make an effort.
I feel thankful receiving so much information.

 

[unpluged]

Quote ScottyUK (The small input is amplified because a fraction of the dynamo output is fed back into a compounding field winding which aids the input winding.)

Do you think it could hold some of the theory and physics of a transformer?
What I am getting at is this.
If the feed back leeks enough to cause a compound reaction to occur, could it be considered in the transformer or step up category?
Please excuse me if I am reaching for more than actually happens, but I hope to just put the question out for debate.
Thanks

 

[davidbeach]

Power out of a transformer is equal to power in less losses, so no amplification from a transformer.

The amplidyne is an amplifier because it uses the input electrical signal to control how much shaft power is converted to electrical power. Electrical power out is much greater than electrical power in, the difference coming from the prime mover turning the shaft.

 

[unpluged]

Power out of a transformer is equal to power in less losses, so no amplification from a transformer.



I understand what you say about the transformer power, but I sure wish I could see this paragraph in an image of the system.

The amplidyne is an amplifier because it uses the input electrical signal to control how much shaft power is converted to electrical power. Electrical power out is much greater than electrical power in, the difference coming from the prime mover turning the shaft.

thanks