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Author Topic: Autoformers, anyone?  (Read 1660 times)

Mike Sokol

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Re: Autoformers, anyone?
« Reply #30 on: October 22, 2017, 08:25:39 pm »

The efficiency is only about 75% to 85% - I often used them in automation projects within factories to supply PLC's. The electricity supply within a factory was often subject to voltage variations and noise because of all the large industrial equipment switching on and off.  They provided isolation, voltage regulation and filtering and would ride through short interruptions. They were also simple and robust and failure was rare.

I installed a few of them back in the day (the 80's), and they ran very hot to the touch (so they were very inefficient) and they made a lot of physical noise.

Tim McCulloch

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Re: Autoformers, anyone?
« Reply #31 on: October 22, 2017, 09:54:31 pm »

I first got exposed to magnetic amplifiers in the 60's (used inside an early switching power supply for current limiting). Pretty old school technology.

As your link notes a ferroresonant transformers is effectively running at (magnetic flux) saturation, so pretty inefficient for variable loads. Clever stuff for the very old days. 

I can't say that I ever saw one in the wild (that I recognized as one).

JR

One of the lakes nearby has a permanent stage and the "friends of the lake" group installed a ferroresonant transformer for audio and stage power.  I remember it was noisy and heated up the switch gear shack.  It was nice having good audio power.  Lights are on a conventional step down transformer.
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Peter Morris

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Re: Autoformers, anyone?
« Reply #32 on: October 23, 2017, 03:06:05 am »

I installed a few of them back in the day (the 80's), and they ran very hot to the touch (so they were very inefficient) and they made a lot of physical noise.

 ... for my application the noise didn't matter - you could never hear them above the background noise in the factories that we installed them in ... production lines that made things like washing machines, steel roofing, gutters, steel car parts etc. 
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Jeff Robinson

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Re: Autoformers, anyone?
« Reply #33 on: October 23, 2017, 04:45:35 am »

... for my application the noise didn't matter - you could never hear them above the background noise in the factories that we installed them in ... production lines that made things like washing machines, steel roofing, gutters, steel car parts etc.

Two observations, never exceed a ferroresonant regulator's maximum rated amperage and if the tank circuit's capacitor fails you do not want expensive gear hooked up. I sold one to a hospital about 10 years ago. Every time I talked to their guy I emphasized that it had to be sized to his load's maximum inrush amperage (medical lab refrigerator needed stable voltage to maintain a precise temperature). He called the manufacturer to get the correct unit after delivery (he knew I would not warranty his sizing mistake). A few years later I sourced a special capacitor to replace one in a different ferroresonant regulator.

My history with this product.

http://www.emersonindustrial.com/en-US/documentcenter/EGSElectricalGroup/brochures-flyers-pdf/pwr-cond-prod-guide-solahd.pdf
Link to Sola's descriptive PDF, they patented them in 1938.

Jeff Robinson

Disclaimer: I sell this product at my work (just not recently).
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David Buckley

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Re: Autoformers, anyone?
« Reply #34 on: October 23, 2017, 06:59:59 pm »

Autotransformers with automatic tap changers are a thing, which do keep a reasonably consistent output voltage.  A full transformer is, for some applications, even better:  The Salicru RE series was a really good example of this, an isolating multi-tapped transformer, with the tap selection done by triac, so it was really fast at following input voltage changes, no more flickering lights.

Underneath that marketing babble is, as ever, a grain of truth; for appliances that are resistive loads, like a kettle, if the voltage is low, then they will use less current, and heat up more slowly, Ohms Law tells us this.

So put two kettles on, or three, then the supply voltage will reduce due to voltage drop, and thus with the reduced supply voltage the wattage per appliance drops.

Marc covered motors, something I'm pretty hazy on!

Stuff with switch mode supplies doesn't care much about supply voltage, it adjusts the current draw to deliver the required output power.

Of course, adding an autotranny to a supply that is already voltage challenged by the load applied will increase the supply current, which will cause further voltage drop, which cannot go on forever, eventually the supply current must exceed the protection device to protect the supply wiring.
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shelley watreen

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Re: Autoformers, anyone?
« Reply #35 on: November 01, 2017, 02:34:55 am »

Yeah...I also think that the description of autotransformer is awful...
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Mike Sokol

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Re: Autoformers, anyone?
« Reply #36 on: November 01, 2017, 07:49:40 am »

Yeah...I also think that the description of autotransformer is awful...
ditto: please change your login to your name. I'm getting all kinds of notifications from the name police... ;)
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