Hot Coil Electromagnet

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Author Topic: Hot Coil Electromagnet (Read 80209 times)

ion	Re: Hot Coil Electromagnet « Reply #25 on: 2012-08-09, 17:14:13 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Here are the current and voltage waveforms into the heater. They are in phase and the power factor measured with a Kill-A-Watt meter is 1.00 showing nearly no inductance. No evidence of spiking in the current waveform. ------------------------ Hot Coil Electromagnet VI_NICR.BMP (303.72 kB, 346x299 - viewed 751 times.) --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Grumpy	Re: Hot Coil Electromagnet « Reply #26 on: 2012-08-09, 18:24:11 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	If the big spieks are at the peaks, then the little ones corrspond to the zero crossings. You say the "phase changes with location", what does this mean in the physical field?

EMdevices	Re: Hot Coil Electromagnet « Reply #27 on: 2012-08-09, 19:25:50 »
Hero Member Posts: 805	Ion, you are correct, the spikes are not from magnetic saturation, since they occur at the zero crossing. thanks for the pictures. What these are is most likely magnetic domain flipping, or barkhouser noise. Nicrome wire is magnetic since it contains nickel, but not very strong. As the wire warms up and the tempeture goes above the Curie tempeture the material is no longer magnetic so these effects die down. Have you guys seen the magnetic thermal "engine" or pendulum that swings and gets attracted to a magnet, but a flame is placed right there as well to heat up the pendulum mass (iron or steel) and as it heats up it looses its magnetism and falls back down, and swings and comes back. It's very neat to watch! EM

Peterae	Re: Hot Coil Electromagnet « Reply #28 on: 2012-08-09, 19:47:26 »
Group: Administrator Hero Member Posts: 3960	Great work ION, it sure is a pretty picture seeing those kicks. I am pretty sure this is what SM wanted us to find and this is why. The shape of those kicks are exactly the same shape i see in the noise i had super imposed on my HT Supply, they were very small, the reason being that the magnetic kick or current kick as SM calls it was being induced inside the valve onto my HT supply or very loosely coupled, this was a clue, when SM said he analysed everyting coming out he must of meant magnetic field as this is where it really shows up. Heat really is a problem and now we know why, too hot and the dam kicks don't show up. I am not sure how close i can get to this because of the valve construction, but i am going off to try and measure the mag field. Happy days ahead. « Last Edit: 2012-08-09, 22:42:50 by Peterae »

ion	Re: Hot Coil Electromagnet « Reply #29 on: 2012-08-09, 20:01:46 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote from: EMdevices on 2012-08-09, 19:25:50 Ion, you are correct, the spikes are not from magnetic saturation, since they occur at the zero crossing. thanks for the pictures. What these are is most likely magnetic domain flipping, or barkhouser noise. Nicrome wire is magnetic since it contains nickel, but not very strong. As the wire warms up and the tempeture goes above the Curie tempeture the material is no longer magnetic so these effects die down. Have you guys seen the magnetic thermal "engine" or pendulum that swings and gets attracted to a magnet, but a flame is placed right there as well to heat up the pendulum mass (iron or steel) and as it heats up it looses its magnetism and falls back down, and swings and comes back. It's very neat to watch! EM EM I've already considered all of what you say. I've considered domain flipping and Barkhousen noise. I'm not sure about either of these being the cause. Yes the Curie point may account for the eventual decay and the magnetic effects of NiChrome surely has something to do with this effect, but NiChrome "C" is extremely weakly magnetic. It is hard to pick up a small coil of it with a very powerful magnet. However, NiChrome "C" has about 24% iron. This site says NiChrome is non magnetic: http://hcrosscompany.com/metals/nichrome.htm And this site : http://www.buzzle.com/articles/properties-of-nichrome-wire.html has this to say: Quote Nichrome is basically a name given to nickel-chromium resistance wires. It is a non-magnetic alloy which consists of 80 percent nickel and 20 percent chromium by weight, and is widely used in heating elements because of its relatively high resistivity. Out of the constituents of nichrome, nickel is an element with the chemical symbol Ni and atomic number 28, whereas, chromium is an element with the symbol Cr and atomic number 24. Nickel is generally a silvery-white lustrous metal and chromium a steely-gray and hard metal. Nichrome, the alloy, is silvery-gray in color, resistant towards corrosion and has a high melting point. The latter two sites are probably talking about Nichrome "A" More research is required before I form any theories. « Last Edit: 2012-08-09, 20:36:39 by ION » --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Grumpy	Re: Hot Coil Electromagnet « Reply #30 on: 2012-08-09, 20:52:55 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	Are the large spikes at the wave peaks or at the zero crossing?

ion	Re: Hot Coil Electromagnet « Reply #31 on: 2012-08-09, 21:11:50 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote from: Grumpy on 2012-08-09, 20:52:55 Are the large spikes at the wave peaks or at the zero crossing? When using the current waveform as a reference, the large spikes seem to occur at the zero crossing. When referred to the sine on the mag probe, they are closer to the peaks. Refer to the scope shots on the prior page. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

EMdevices	Re: Hot Coil Electromagnet « Reply #32 on: 2012-08-09, 21:19:47 »
Hero Member Posts: 805	this is a link to a Curie tempeture demonstration with nichrome wire. http://www.tarangscientificinstruments.com/manuals/Curie-Point.pdf [edit:] Can I interest anybody in a Curie Motor? we can probably design this with nichrome wire as well and place electrical contacts on the rim to heat up the sector that needs to be above the curie temperature. The current flow could produce some electrodynamic forces, so that's why I'm using a laser beam, to show that it is strictly heat that renders that section of the wire non magnetic when the temperature is above the Curie point. ------------------------ Hot Coil Electromagnet curie_motor.JPG (36.97 kB, 902x541 - viewed 720 times.)

ion	Re: Hot Coil Electromagnet « Reply #33 on: 2012-08-09, 21:29:58 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Quote from: EMdevices on 2012-08-09, 21:19:47 this is a link to a Curie tempeture demonstration with nichrome wire. http://www.tarangscientificinstruments.com/manuals/Curie-Point.pdf We can agree that the Curie effect is responsible for the eventual decay of the pulses. We need a good explanation for the cause of the pulses. Explanations thus far have been rather weak. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Grumpy	Re: Hot Coil Electromagnet « Reply #34 on: 2012-08-09, 21:36:00 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	half wave rectify power to the heater (i.e. chop off the bottom half) Then, do you still have the spikes and noise? ( I d not think you will.)

EMdevices	Re: Hot Coil Electromagnet « Reply #35 on: 2012-08-09, 21:38:06 »
Hero Member Posts: 805	since those spikes occur very close to the zero crossing, as the current changes direction and the magnetic field reverses, the Barkhausen noise is the best explanation I can came up with because that's where it occurs, right when directions change. Why it is occuring in one solid burst is a bit puzzling, but it could be becasue we are dealing with a wire and not a core. In a wire, if one domain flipps, it starts a chain reaction and it could trigger other domains in a avalanche mode, and the wire having a very small cross section than triggers everything at once, as opposed to a core. That's my thinking at least, but research is needed to prove it. I'll do some searches on the internet see what I can find. @Grumpy, correct, we won't see them if the reversal does not occur. EM

EMdevices	Re: Hot Coil Electromagnet « Reply #36 on: 2012-08-09, 21:58:14 »
Hero Member Posts: 805	Ion is right, we need to ponder this some more. I just studied the picture he posted more closely, and I don't agree that everything we see is Barkhausen effect. The zero crossing could very well be due to the Barkhausen effect, but the other spikes are CLEARLY due to a change in resistance which we can see in the current waveform as a discontinuity in the slope which I circled in red. Remember, a discontinuity in current, represents a large dI/dt, and the induced voltage in a coils is proportional to it, so a very slight change in the waveform produces large magnetic changes which produce by induction large voltage spikes in the pickup coil. The question to answer is, why is the resistance sudenly changing? or is it? what if it's the voltage source that is flaking out? there is clearly a dicontinuity in the slope of the current waveform and that's what interests me at the moment. EM ------------------------ Hot Coil Electromagnet ion_effect_explain01.JPG (96.13 kB, 1170x948 - viewed 720 times.)

Grumpy	Re: Hot Coil Electromagnet « Reply #37 on: 2012-08-09, 22:00:41 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	Quote from: EMdevices on 2012-08-09, 21:38:06 @Grumpy, correct, we won't see them if the reversal does not occur. EM Also, you will not see it if the AC wave is biased above zero as there is no reversal. That looks a little strong for Barkhausen noise. Can you measure the electric field near the magnetic probe? or place some sort of charge indicator there?

Peterae	Re: Hot Coil Electromagnet « Reply #38 on: 2012-08-09, 22:01:22 »
Group: Administrator Hero Member Posts: 3960	I am seeing other pulses as well just after the maximun pk is reached and then the sine changes direction, but interestingly these are half the height and interestingly these also seem to distort the sine slightly. In the UK it's possible to buy small lower power quartz tube heating elements which are sold as replacements or spares. A lower power version of ION's heater is needed so we can run from a variac, this way we maybe able to stop it getting to hot, it will also be possible to see the pulse amplitude with relation to the current drawn. http://www.tlc-direct.co.uk/Products/DXPH08001.html?source=froogle Although as ION states one can be wound with nichrome. I have a reel of stainless steel wire which if i can work out how long i need to wind it for our mains i maybe able to wind one, stainless steel is not magnetic.

EMdevices	Re: Hot Coil Electromagnet « Reply #39 on: 2012-08-09, 22:07:59 »
Hero Member Posts: 805	Peter, I guess we're all posting at the same time. See my picture in my previous post. For all that are not familiar with induction, the basic formula for the voltage induced is V = - N * dphi/dt, where, 'phi' is the magnetic flux, 'N' the number of turns. This says that the voltage induced in a coil of 'N' turns is proportional to the number of turns and the RATE OF CHANGE of the magnetic flux through the coil. So, note what is important here, the RATE of change, and NOT the MAGNITUDE of the magnetic field. As a consequence, we can have a very weak field that changes rapidly, and it will induce a higher voltage than a stronger field that changes slowly. (current produces the magnetic field, so it indirectly depends on the curent as well, and we should all know the basic inductor formula V = L di/dt, which is just another form of Faraday's induction equation) This is what SM was trying to explain, with his weak magnet moving very fast past the coils, analogy. EM

Peterae	Re: Hot Coil Electromagnet « Reply #40 on: 2012-08-09, 22:17:36 »
Group: Administrator Hero Member Posts: 3960	Sorry EM Let's not forget the whole picture here, someone needs to do a spectrum plot on the audible noises from his coil, i am leaning towards harmonics of 60Hz in the US and up into the kHz as well.

EMdevices	Re: Hot Coil Electromagnet « Reply #41 on: 2012-08-09, 22:21:45 »
Hero Member Posts: 805	yes, that's what I would expect as well, i.e. harmonics of the 60 Hz (in the US) and 50 Hz in europe and elsewhere. by the way, a bread toaster produces the same noise when turned on, and transformers have the same noise, but it does not decay because the temperature does not exceed the Curie temperature. The cause of this noise is the famous magnetostriction properties of magnetic materials, i.e., changes in length due to magnetisation. EM

ion	Re: Hot Coil Electromagnet « Reply #42 on: 2012-08-09, 22:29:41 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	EM said Quote In a wire, if one domain flipps, it starts a chain reaction and it could trigger other domains in a avalanche mode, This is more in line with what I've been thinking, and maybe what SM was trying to teach. Consider also that it might be a bulk electron effect, with unpaired electrons being aligned in a certain direction as the sine current increases, then instead of slowly relaxing to their former position as the sine proceeds towards zero, they flip all at once to zero by going "over center". and: Quote The cause of this noise is the famous magnetostriction properties of magnetic materials, i.e., changes in length due to magnetisation. I can totally agree with this........but the radiated spikes keep me guessing. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Grumpy	Re: Hot Coil Electromagnet « Reply #43 on: 2012-08-09, 22:38:31 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	ummm Isn't this effect measured outside the wire? So, what's flipping?

EMdevices	Re: Hot Coil Electromagnet « Reply #44 on: 2012-08-09, 23:23:49 »
Hero Member Posts: 805	@ Grumpy, what's flipping is the magnetic domains inside the wire. The magnetic field is very strong the closer it is to the current, and the wire is slightly magnetic due to Nickel. @ All, looks like these guys beat me to it. I never have any original ideas! http://www.oberlin.edu/physics/catalog/demonstrations/em/curiemotor.html but maybe nobody has thought of this, how about a solar Curie motor, that should be original! EM ------------------------ Hot Coil Electromagnet curie_motor02.JPG (56.34 kB, 866x830 - viewed 665 times.)

Grumpy	Re: Hot Coil Electromagnet « Reply #45 on: 2012-08-09, 23:33:52 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	Quote from: EMdevices on 2012-08-09, 23:23:49 @ Grumpy, what's flipping is the magnetic domains inside the wire. The magnetic field is very strong the closer it is to the current, and the wire is slightly magnetic due to Nickel. but maybe nobody has thought of this, how about a solar Curie motor, that should be original! EM and it makes a spike like that 1.5" from the wire When nichrome is barely magnetic if at all

ion	Re: Hot Coil Electromagnet « Reply #46 on: 2012-08-09, 23:47:55 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Ok guys I wound up 100 turns B&S #19 0.036" dia Nichrome on a 5/16 ceramic mandrel. I don't know if this is type A, C or Tophet. The roll only said Nichrome, Nickel plated. I cannot detect anything like the other scope shots with the mag probe. I don't hear any buzzing either. Don't run off and buy any heaters until I figure this out. My original heater is a Martel Quartz Glo Model Q15T. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Grumpy	Re: Hot Coil Electromagnet « Reply #47 on: 2012-08-09, 23:53:38 »
Group: Tinkerer Hero Member Posts: 3948 tExB=qr	regarding the heater itself and probing it, can you somehow add a lot of dielectric to the probe? If it is a coil, can you put plastic inside (like a rod) and outside (like a tube)? Or put it in a plastic container? or other dielectric. and see if it "changes the nature of the detected pulse". Sounds crazy but I expect it will change the pulse "significantly".

EMdevices	Re: Hot Coil Electromagnet « Reply #48 on: 2012-08-09, 23:54:45 »
Hero Member Posts: 805	@ Grumpy, sure, even 100 ft away from a single wire that carries a current of maybe 0.001 amps, if you interupt the current "instantly" you can generate an "infinite" voltage spike. Like I said, it is not the magnitude that counts but the rate of change. Let's think about a nuclear explosion and the EMP pulse, most people think that it is some STRONG and POWERFUL magnetic field that causes the effect, but in actuallity, it is not so much the magnitude of the magnetic field, but the RAPIDITY AND EXPLOSIVENESS of the chain reaction that creates the CHANGE in the magnetic field which induces large voltages far away. So, rapid magnetic changes = higher induced voltage. Faradays law of induction in a nut shell. @ Ion, the sound can be heard if the construction is condusive to it, i.e. if it amplifies or couples well to the air, like a speaker, otherwise there is movement but poor acoustic coupling to the air. Another thing to consider, now you have 100 turns, so your resistance is a lot higher, so now your power disipation is lower, and maybe your wire does not heat up to the same temperature, or the current is not so high to produce the effect. The magnetic field is proportional to the current so if its not as high perhaps it won't work. keep stroking this problem, it's very interesting from multiple points of view .. EM « Last Edit: 2012-08-10, 01:14:06 by EMdevices »

ion	Re: Hot Coil Electromagnet « Reply #49 on: 2012-08-10, 00:03:53 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	EM said: Quote the sound can be heard if the construction is condusive to it, i.e. if it amplifies or couples well to the air, like a speaker, otherwise there is movement but poor acoustic coupling to the air. Another thing to consider, now you have 100 turns, so your resistance is a lot higher, so now your power disipation is lower, and maybe your wire does not heat up to the same temperature, or the current is not so high to produce the effect. The bagnetic field is proportional to the current so if its not as high perhaps it won't work. Actually my resistance is less on the hand wound coil, 3.56 ohms versus 9.56 ohms for the larger unit. I run the smaller coil at it's limit, around 6 amps. There might be something different about the wire used in the Martel heater, so I have to dig deeper. I understand about the acoustic coupling to the frame. G: I'd like to run more tests as time permits but it is getting too hot in my house --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

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