EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: avitsur on December 09, 2023, 02:17:22 pm
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I'm looking for an ac power supply that can work like a variac ranging from 0-230vac.
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Power level?
Frequency?
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...
Why a Variac isn't suitable?
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Two reasons. I don't have one and it's bulky.
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What you are asking for is a function generator driving an overload protected power amplifier. At typical AC mains voltages and currents said power amplifier wont be small, cheap or easy to design. Its only *worth* doing vs a Variac if you need variable frequency.
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I don't have one and it's bulky.
If you don't have one, you can buy one (or steal one).
As for bulkiness, you haven't given any size or weight specifications.
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Two reasons. I don't have one and it's bulky.
Unless you only need a very small amount of power (signal level) acquiring a Variac, plus an isolation transformer if needed, is going to be the simplest, cheapest and most compact solution. What is your intended use of the supply?
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If you would be fine with less fine control, you could just buy a 230v - 230v toroidal transformer and unwind it to create lots of taps on the secondary side, like for example every 5v AC - 46 taps.
Then buy yourself a bunch of mechanical relays and code something that takes out or puts in secondary windings.
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hello avitsur,
it is an interesting topic, I once designed and made a such instrument,
what i needed :
a 230V AC RMS clean SINE, constant frequency, constant voltage output,
no matter how much mains voltage variations, only 100watt needed.
how i did it:
crystal controlled microcontroller made the 50Hz / 60Hz selectable mains frequency from sine table and pwm
mains transformer bridge and caps, just classis high voltage supply
then a 100W audio amplifier board and heatsinks, i went for linear class AB for cleanest result.
then a step up transformer, since the audio amp cant deliver 230V but the amp can deliver 30Volt
so a step up fra 30 to 230 is needed.
feed back : i really wanted global feedback (from output of step up transformer) this way i could get zero output impedance,
however this is not possible the normal way, due to phase shiftings in loads and in transformer,
my next will be class D amp, and output rectified and then level feedbacked
this way it should be stable and low impedance.
Performance : this does outperform a variac in voltage resolution, distortion stability, BUT
size and cost : it is bigger, more heawy, and more expensive over a variac, and a variac can deliver much more power pr weight.