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Telsa coil capable of stepping down voltage?

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GammaRay

Sat Oct 19 2013, 02:39PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
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Posts: 104

I am trying to find an efficient method to step down 800v-1kv (+/-) at low amperage to around 12 volts DC (+/-). Already built a buck converter which does an okay job, but hoping to find a more efficient way. Question: Anybody on this forum ever heard of a Tesla coil being used in reverse to step voltage down? (Already checked the archives).

Ash Small

Sat Oct 19 2013, 03:07PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

GammaRay wrote ...

I am trying to find an efficient method to step down 800v-1kv (+/-) at low amperage to around 12 volts DC (+/-). Already built a buck converter which does an okay job, but hoping to find a more efficient way. Question: Anybody on this forum ever heard of a Tesla coil being used in reverse to step voltage down? (Already checked the archives).

Well, they do work as 1:1 ratio transformers, I built an air core Xformer with 10 primary turns and ten secondary turns to superimpose the HF signal onto a DC current.

HV Enthusiast

Sat Oct 19 2013, 10:26PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Firstly, a Tesla coil is not an efficient way to step-down or step-up voltage. Its an easy way to get high voltages, but not very efficient.

I guess the question begs to ask is why you need to step down such high voltage to 12V when you can easily get 12V from an off-the-shelf wall source or battery.

Plus, you don't need a Tesla coil to step-down voltage from 1kV to 12V. Assuming low frequency, a simple transformer will do that off-the-shelf 50/60Hz or you could wind one yourself if its a higher frequency (i.e 100's kHz)

BigBad

Sat Oct 19 2013, 10:55PM

Registered Member #2529 Joined: Thu Dec 10 2009, 02:43AM
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Uh. Yeah?

You do know that that's what Tesla coils were invented for?

Tesla's wireless schemes had a few different versions, but pretty much they all involved stepping up voltage to very high voltage, and electrostatically coupling across, and then using a second Tesla coil to do the step down.

I mean it doesn't work spectacularly well as a way to do wireless power, but Tesla coils do step up and step down fairly well (depending a bit on what you mean by 'well', each Tesla coil can be about 85% efficient or so ish).

Dr. Dark Current

Sun Oct 20 2013, 09:02PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Just use a normal SMPS, efficiency of ~90% should not be unreal. Bridge or two switch forward converters can be stacked in series, so you can use MOSFETs or lower voltage IGBTs.

GammaRay

Sun Oct 20 2013, 10:11PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
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Posts: 104

Looking for a SMPS that can handle 800 v DC input.

GammaRay

Sun Oct 20 2013, 10:50PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
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Is this generally the type design you are speaking about? Thanks in advance.

Steve Conner

Mon Oct 21 2013, 09:24AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Yeah, devices like that are commonly used in industry to power the control circuitry in big motor drives off the DC bus. You can just buy one off the shelf.

The input voltage is nominally about 600V but they allow a fair bit of headroom.

That one probably uses 1200V IGBTs, but you could probably get better performance nowadays using silicon carbide FETs.

Tesla coils do indeed function in the step-down mode. I once saw a spark-gap coil destroy a solid-state one that was sitting unpowered nearby. It charged up the DC bus caps on the solid-state coil until the transistors went boom.

GammaRay

Mon Oct 21 2013, 03:26PM

Registered Member #5323 Joined: Fri Jun 15 2012, 02:14PM
Location:
Posts: 104

Here's another choice. With either one, I'll spend around US$100, so I'd like to select the best one. If it were your choice, which of these two would you select? Or is there another one that would be even better that I haven't found yet? (such as one with the recommended Silicon Carbide FETS).

Chris Cristini

Mon Oct 21 2013, 10:29PM

Registered Member #1749 Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497

Silicon carbide is very interesting technology New generation SSTC's.

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