Induction Cooking Table : IGBT keeping to short !

[William Sommerwerck]

Corning paid the postage to return it, but they never told me
what they found (if anything). They made no offer to replace it.

Did you send it to the real Corning or the fake place called "World
Kitchen."

The latter.

It's not actually fake. According to the Wikipedia article, World Kitchen
was originally Corning's Consumer Products division.

I'm bothered by companies buying up trademarks, then applying them to
products that have no connection with the trademark's original usage. Pyrex
is a good example of this bad practice. So is Accutron. Modern Accutron
watches do not use a tuning fork.

 

[cLx]

Phil Allison wrote:

jurb6006@gmail.com> wrote:
cLx wrote:
"When it was brand new, i've measured the frequency at ~35KHz,
modulated by 100Hz (double rectification of the mains' frequency. "
So they don't bother filtering, like a microwave. Hmmm.
** Microwave ovens have similar line frequency modulation and for the same
reason.
The high voltage PSU is not filtered.
Electronic transformers for 12v halogen lighting are the same too.

No big DC filter capacitors means you'll not have huge peaks two times by
mains cycle. Better power factor, in fact, it's almost itselfs a PFC

 

Actually I have a pretty novel idea I am thinking of trying to implement. An audio amp with only one output device hopefully, if I can find a fast enough triac type device (a few kinds would work). Would advance the phase of the triggering pulses according to input and switch off automatically when the HF power cycles. No filters or even rectifiers. If I can't do it a triac I can use a bridge rectifier and do the same thing with a fast SCR, or even a tansistor. The only advantage to a transistor though is that it would be switching off at zero crossing all the time. Still no filters.

It would have all the problems of a class D amp but less components and you could probably use slower output device(s) or a higher frequency.

I almost decided to patent it but I found some things that are just too damn close. Convertors for VFDs running off three phase mains, with no recitification. It was interesting anyway.

I might take a crack at it one day, the problem is designing the trigger circuit, there is not going to be a chip that'll do what I want - yet.

But we are talking more efficient than class D if I can pull it off. Also in my [discouraging] research I found there is another type of class D amp out there now, it uses active filters almost instead of analog outputs. The class D part always keeps a pretty constant voltage across the analog devices keeping their dissipation down. The manufacturer claims efficiency nearly as high as class D but without the sonic anomalies that those golden ears dudes can hear.

The days of linear operation may really be at an end. Don't even bother to rectify or filter ? Chop chop chop, nary a watt dissipated.

Enough commentary now, we can start a thread for that. I would never mention my idea except I DID find out that it is unpatentable. If perchance I ever do build the thing I will get a provisional patent and see which way the wind blows. It's only a hundred bucks.

Of course I think in that case every Eurasian engineer out there will look at it and by the time I get to market there will be three products like it, two challenges to the patent and more legal bills than I could ever make on one product.

Such is life. I need to look for something even wierder to build.

Speaking of which, I happen to own one of those induction cooketops and I would like to do something with it. Maybe I could make a weapon ? I got some microwave parts hanging around for the same reason.

 

On Tuesday, November 20, 2012 at 12:20:17 AM UTC+5:30, cLx wrote:

Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :
http://clx.shacknet.nu/random/IMG_5802.JPG

And a little picture of the board :
http://clx.shacknet.nu/random/IMG_5803.JPG

Thanks !

There are couple of transistors for drive the IGBT. replace those transistors and your problem will be solved.

Thanks