inverting high voltage

The real application defines what way to do it. Basically, the total amount of misery in the universe is a constant. By doing the design you mainly get to choose which kinds of misery you prefer over other kinds. Some people call one lump of broken stupidity "better" than another sucky piece of thrash depending on the frame and the purpose of the thing.

Until you know: "what is it for?" and "why do you want it??" you are asking a null question.

This isn't a theoretical issue, it's a commonplace one in power circuits. For example, modern washing machines have VFD motor drives, or Variable Frequency Drives. These work by rectifying the ac line voltage to get about 340V dc, etc., and then use six IGBTs wired in bridge mode, chopper operated by a special PWM controller, to make a 220V three-phase variable-frequency AC for the motor (I imagine it's 220V ac that's created). So, the 340Vdc is like your theoretical 500V battery, and the motor's AC power is like your destination. Now, for 1kW and 2kW most people would stick with about 340Vdc instead of going higher, because at this lower voltage you can use common, inexpensive 600V IGBTs. But for much higher power levels there is a family of inexpensive 1200V parts, and there's a 680Vdc or so region of use, but I'd guess that's common only for 5kW, 10kW, or higher power levels.

The real application defines what way to do it.

--------------------------------------------------------------- I have written this under "goal" line and this is the main goal ( in some future time ).

Thnx in advance !

Thank you for your replay! I have found some web sites regarding IGBT's.

Question: As you have read, in my first idea i have low power ( 0,5 A ).

2.) What would you do to reach the "goal" part ?

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OK. this are questions for now :-)

Mark

Hello Winfield,

That ought to the the top of the line breed of washers. Ours has simple contactors that turn the motor on at various power levels, plus a gear box where they didn't even spring for a clutch (KA-Clunkkkkk). Manages to pretty much ruin a shirt collar within 30-40 washes :-(

You can do it several ways:

(1) If the "batteries" can be separated into ten 50V sources, you can have some hefty FETs connect them in series and parallel in various combinations to make a pretty good approximation of a sine wave (with maybe an output LC filter for smoothing).

(2) If the load can have both wires "hot" and floating, you can make a PWM circuit to chop up the DC voltage into a noce 50Hz sine wave.

(3) If the load needs one side grounded, you probably need a transformer in there too.

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Note that at this power level in the average design and debugging process you're going to blow a dozen or more of these non-cheap power devices, until you learn about spurious oscillations, transients, spikes, inductance, and SOA limitations.

On Thu, 26 Oct 2006 11:07:46 +0200, "Frithiof Andreas Jensen" Gave us:

A full floating HV supply can be used with either positive or negative line grounded.

Until you know what you are talking about YOU are a nul answerer.

On Thu, 26 Oct 2006 21:27:26 GMT, Joerg wrote in Msg.

Until the IGBT/three phase stuff is cheaper (and more reliable during warranty) than the relays and gearbox, which probably is about right now.

robert

On 25 Oct 2006 11:55:03 -0700, mark2006 wrote in Msg.

I'll buy ten of those.

robert

of

one

depending

Then be a clever boy and go solve the O.P.'s question now that The Voices told YOU what his/her/she/it is up to.

Do Buy a new one!

The one you have is wasting water and electricity. Mine is a five year old AEG that cost around USD 600 in todays devalued money - that is fully electronic. There is a disc-motor on the drum and a white box of electronics next to it and the usual pumps and sensors. *Everything* is wired to the controller box. I uses about 16 liters of water per wash - you can go down to 10 now.

PS: I had to change the brushes once - the motor is some cross-breed of an induction motor and a dc motor; it looks like a three-phase stator and a rotor with normal commutator. Undoubtable part of some ninja-trick to reduce costs.

I think our Hoover w/m has a good solution. It's a beefy series-wound universal motor, with reversable field coil and a simple hall effect speed sensor. It is PWM'd with a Triac, straight across the 240Vac mains. The control board is tiny, about 3"x2", with barely anything on it. The bidirectional speed control is smooth, with the drum being controlled from about 10rpm up to 1400rpm.

On a sunny day (Thu, 26 Oct 2006 21:27:26 GMT) it happened Joerg wrote in :

I have seen that system used in centrifuges. I mean professional ones, not for washing, more for plutonium and other chemicals.

Yes of course. My technician's 6-year-old washing machine failed recently and they wanted $500 for a new circuit board, so I learned the details of its electronics to repair it. The Sears Kenmore design was sophisticated 3-phase VFD with an Analog Devices DSP and IR IGBT drivers and IGBTs. But it used a simple, cheap 340V to 16V converter, which failed and wiped out ICs, IGBTs and all kinds of stuff. The Kenmore design used six reasonably-hefty IGBTs to make its 3-phase sine waves; the IGBTs cost only about 60 cents each, IIRC.

You can get small 600 to 1200-volt MOSFETs, but, for voltage ratings of 400V or higher, an IGBT of a given die size can carry more current than a same-size MOSFET. An IGBT costs less and delivers more performance. But you can certainly find nice small-die IGBTs for modest-power applications.

These PWM power converters are quite efficient, so simple load-power and battery-energy calculations should work.

My MayTag washer just passed its 27th birthday. In that time it's gone through one timer replacement ($66) and two belts ($16). The timer is your basic slow motor turning some cams and switches. It even survived the time a tree fell across our 4400 volt power line and zapped most everything electronic in the house that was turned on, and even some things that were'nt.

Think I'll stick with LOW TECH in this field until forced to do otherwise.

Hello Frithiof Andreas,

Nah, only when ours breaks and can't be repaired anymore ;-)

uses

Well, those Miele frontloaders we can get here sure are nice but a whole lot more expensive than in Europe. I haven't seen anything under $1000 there. Also, much of our electric grid is above ground and you'd have to trust the engineers of those controller to have done an excellent ESD job. Unfortunately I have seen too much grief there, failure to place series resistors in sensor lines etc. Like our furnace controller, one power glitch, bzzzt. $400+ and a new controller later it worked again (for a while).

Same here. Keep it simple.

it's not new technology the local (NZ) manufacturer (Fisher & Paykel) calls it "Smart drive" the three-phase synchronous motors from old washers are finding new life as generators for wind turbines.

Bye. Jasen

@ Winfield Hill @ Ancient_Hacker

------------------------------- Can i send you e-mail with project description ? My e-mail is the same like on the groups.

Now i have basic idea what i want and i want to skip the forum part.

Mark