Is there such thing as a switchmode variac?

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Is there such thing as a switchmode variac and where can I get one?

A google search seems to only turn up links to testing switchmode power
supplies by using a variac on the input.

Failing that, I suppose you could cannabilise the sinewave output stage
of a 12-240 inverter and bung it on the end of a variable high voltage
DC supply?


Re: Is there such thing as a switchmode variac?


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Yes: Episode #27 of "Flash Gordon", Dr Zarkov uses one to
kickstart the rocket motors on Flash's spaceship after the
lithium ion cells fail.

Re: Is there such thing as a switchmode variac?



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Im sure that you could do that (If you know what you are doing) but
why would you bother ?

Re: Is there such thing as a switchmode variac?


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Most likely not.

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Most probably, but why bother? What is wrong with a standard variac?

Dave :)


Re: Is there such thing as a switchmode variac?


snipped-for-privacy@hotmail.com wrote in news:1157355573.625800.244310
@m73g2000cwd.googlegroups.com:

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There are supplies that can do that designed for EMC mains fluctuations/
flicker etc. They can simulate brownouts and are programmable. They would
probably work like a variac but they probably only go to 20-30 amps. They
will cost $5000 or more. (one brand I've seen is "Best") A 30 amp variac is
probably about 1/0th that price. What exactly do you want to achieve?

Re: Is there such thing as a switchmode variac?


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I wanted to be able to control a variac by a PC/uC.  I was guessing
that an interface to the switchmode variac would be as simple as a low
voltage control input in the feedback loop somewhere.

The other low-tech option I was thinking of was a motor (with
positional feedback) driving the variac knob.


Re: Is there such thing as a switchmode variac?



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It's not all that difficult. About 1988, we connected a geared dc motor to the
knob
of a variac. The output voltage and current were displayed using 3.5 digit LCD
modules.


Re: Is there such thing as a switchmode variac?



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or a 50Hz oscillator - feeding a digital volume control chip - feeding a
power amp (an AM1600 will give 110V RMS or so out )  maybe feeding a
Transformer (better watch the DC offset of the amp then - I dont think an
AM1600 would work here ...) depending on what Voltage range you want ....
Bit complex isnt it ? the Motor feeding a Variac would be cheaper/easier
....



Re: Is there such thing as a switchmode variac?






**  A hotmailer and Google Groper  -  double whammy  !


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 **  Yep  -  it is called a " sine wave dimmer ".



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**  The latter is just as scarce as what you first asked for - dickwad.



......  Phil






Re: Is there such thing as a switchmode variac?



Phil Allison wrote:

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                        ^^^^^^^

why be a wanker ?

The guy might be asking an idiotic question, but we were all like
that at one stage.

Fred


Re: Is there such thing as a switchmode variac?



< snipped-for-privacy@gmail.com
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 **  Don't I know you  ?

Your name is very familiar from the early '70s.





.......  Phil




Re: Is there such thing as a switchmode variac?



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I very much doubt there is such a beast as a switch mode variac.
However, you can get motorised variacs which can be externally
controlled, but they won't be cheap...
http://www.australianrectifiers.com.au/motorised.htm

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