I read on another site that the item linked to in the first post suffers from reliability issues, has a tendency to blow its power switching devices….

How true this is, I couldnt say, but it would be remiss of me not to tell……..

I am trying to work out how I missed the earlier thread. Mind you, it was only "open" for less than 2 days.

Has any one tried using an induction heater for model engineering work?

JA

Breda, I have had an interest in this type of heating for some time and recently saw this unit on an American site. I have purchased one but not had time to play with it yet, I'll report back when I have

John

Edited By JohnF on 17/04/2016 15:14:16

You may find the output of your welding transformer too high…..you need to measure the ac voltage.

Then you will need some big diodes……capacitor wise, the working voltage will be based on the output of your welder…capacity wise, depends on how much ripple the induction unit can tolerate….if its small, then big capacitors….

Three 12v car batteries will power it….for a while…..

I have one of these **LINK** – have used it for freeing bolts etc., also for warming a hydraulic jack body after degreasing to make sure all water evaporated before re-assembly. I haven't yet tried it as a heat source for silver soldering, I think it might work for that.

It's a potentially handy piece of kit, but difficult to justify the cost for occasional use.

The limits seem remarkably low. I've worked with automotive wireless chargers (up to 30kW or so) and stray fields are one of the restricting factors that the developers have had to contend with but they are not insurmountable.

Having spent most of my career in power electronics, I can safely(?) say that I've been exposed to much stronger fields on a very frequent basis. Seems that heating of the organs is considered to be the main risk (rather like microwaves) due to the fact that most of the fluids in our bodies are conductive hence prone to induced currents. However, I've never noticed any kind of discomfort.

The skin thickness at frequencies of 50-200kHz where most of my work was done is dependent on conductivity but that should be fairly high (ie conductive), so you'd think it wouldn't be more than a few cm, so in my case I'd expect my fingers (also much closer to the source of the stray fields) would be the first to tell me.

Murray

There is a fair amount of info on people playing around with them on the web Jack. The screwdriver seems to be pretty typical or similar sized things. Some people play with connecting high current supplies in series to get more volts. One person I noticed used to server power supplies in series. These are usually 12v and lots of amps. As they are made by companies such as HP they are also well made. Usually there is a need to find out how they switch one after being plugged into the server. There is some information about that on the web because model aircraft people etc make high powered battery chargers out of them. It usually just means jumpering a couple of the connection in their socket.

Connecting them in series involved opening them up to isolate the chassis. The units can be surprisingly cheap on ebay.

I wonder if people are confusing microwaves with boiling stomachs etc. Induction heaters operate at much much lower frequency than microwave cookers. Those use one that causes water molecules to vibrate and generate heat – the frequency is not far off what one of the mobile phone bands use. As I understand it induction heating works by causing current to flow in the part. With enough power they can make things glow very red hot. Past cherry I would say.

John

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This is me on the right of the picture in around the early 1960's at Mullard Ltd casting a similar alloy to Nimonic with an induction furnace, I think it was around 10KW, not quite sure of the frequency but it wiped out the BBC Light programme when running.

John

Edited By Sandgrounder on 02/05/2016 19:33:24

From memory and room for error it's circa 100 odd khz. Likely to increase as semiconductors do. It's likely to be a essentially a square wave drive which means that there will many higher harmonics.

I've seen parts going along a production line suddenly glow red hot as they pass through the field off the coil. Bulpitt who used to make Swan brand items. Their site was the pits but some of the technology they produced was amazing. Bought out by Moulinex eventually.

John

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