Possible to turn a piece of pipe/tube into an induction heater?
Possible to turn a piece of pipe/tube into an induction heater?
(OP)
I have been researching induction heating as of late and last week I found a site that showed a metal tube with two AC leads going to it (one at each end). The voltage was stepped down to something reasonable so that someone touching it when there is the hopefully unlikely grounding/neutral issue would not be fatal.
I tried to find the site again but couldn't. Then I found hundreds of sites showing an induction heater as a coil around a conductive object, which makes a whole lot more sense to me in terms of the word "induction" being used.
Perhaps the simple tube heater (intended to heat whatever is inside the tube) was actually a resistive heater, with the tube being the resistance? I just can't see how the resistance of a piece of pipe could ever be high enough to not cause an over draw dituation.
Thanks for any knowledge shed on this topic.
I tried to find the site again but couldn't. Then I found hundreds of sites showing an induction heater as a coil around a conductive object, which makes a whole lot more sense to me in terms of the word "induction" being used.
Perhaps the simple tube heater (intended to heat whatever is inside the tube) was actually a resistive heater, with the tube being the resistance? I just can't see how the resistance of a piece of pipe could ever be high enough to not cause an over draw dituation.
Thanks for any knowledge shed on this topic.





RE: Possible to turn a piece of pipe/tube into an induction heater?
First, there is no magnetic field inside a tube. If you think of the tube as a lot of strands connected to rings at the end of the tube, you will easily see that the individual magnetic fields cancel. Some magnetic field can be measured close to the tube inside wall, but it is not an efficient way of producing a heater.
Next, a heater working with small dimensions cannot use 60 or 50 Hz. A typical heater that is used to heat large steel pieces for forging presses uses 500 - 1000 Hz and smaller heating coils for welding use much higher frequencies.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Possible to turn a piece of pipe/tube into an induction heater?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Possible to turn a piece of pipe/tube into an induction heater?
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: Possible to turn a piece of pipe/tube into an induction heater?
These days too complications arise. Non metallic piping, insulated joints on metallic piping, possible damage arising from stray heavy ground currents; the list continues.
Mainly though, building codes now require domestic water services to be buried much deeper and freezing is no longer the frequent issue that it was years ago.
Bill
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"Why not the best?"
Jimmy Carter
RE: Possible to turn a piece of pipe/tube into an induction heater?
RE: Possible to turn a piece of pipe/tube into an induction heater?
I would love to turn my vessel into a resistive heater, just have to figure an economical way to step 115 / 220 down to say 5 volts or so. I guess an 'ol transformer it the only way to go.
By the way, I am a mechanical engineer, not electrical, so kindly excuse my ignorance here :)
RE: Possible to turn a piece of pipe/tube into an induction heater?
It is common for induction coils for large heaters to be made from common copper water pipe. It's not clear in your post if this is what you were looking at. This units that I have worked with can carry currents of around 500-1000 Amps. I think you may be missing the science behind induction heating: the heat is not created by power transfer through the resistance of the pipe, but rather by the current around the pipe (bent into a coil shape) inducing currents into the target material (which mas be ferrous), and those currents heating the target. The induction of these currents is done at high frequencies, up to 10KHz, and the black magic in large induction heaters is tuning the heater to the optimum frequency. The coil design, how many turns of the pipe, and it's diameter etc., and the material being heated greatly effects the amount of heating. Adding to the complexity, as the target material heats up its magnetic properties decrease so there is a lot of tweaking to obtain an optimum power transfer.
Another interesting fact, induction heaters are one of the few remaining applications that still use vacuum tubes to create the oscillating signal required for the induction. Of course, these vacuum tubes can cost upwards to $1000 each, and are water cooled. Also, the copper piping used as the induction coil will also have water flowing through it since copper can not be heated to the same temperature as the target ferrous material (aka steel). It's a very interesting field, and I have a customer who uses induction heating while epoxy coating rebar, which is how I am familiar with it.
Frank
RE: Possible to turn a piece of pipe/tube into an induction heater?
At the far end of the circuit, the single power wire is connected to the heating tube so the tube is the return circuit. Due to skin effect, most of the current flows on the inside wall of the heat tube, raising the resistance. A single phase power supply is connected at the near end.
It is a very practical and safe solution for heating long runs of pipe. Power supply points can be located much further apart than if normal heating cables were used. (15 miles, 25 kM)
But, I don't see how this design would help your application.
http://www.thermon.com/US/products.aspx?prodid=10
RE: Possible to turn a piece of pipe/tube into an induction heater?
They like to use copper tubing for the RF coil, since you can pass cooling water inside of it, and keep the copper from melting.
Not the sort of project a neophyte should tackle, as there are high RF voltages and currents involved--could be some safety issues.
www.MaguffinMicrowave.com
Maguffin Microwave wireless design consulting
RE: Possible to turn a piece of pipe/tube into an induction heater?
It's not induction heat though, purely resistive.
RE: Possible to turn a piece of pipe/tube into an induction heater?
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If we learn from our mistakes I'm getting a great education!
RE: Possible to turn a piece of pipe/tube into an induction heater?
Probably burnt fingers , and so much RFI you best live on a ranch in USA. If you want to home brew this !