After reading some of the comments about needing a very high voltage to reverse polarity as quick as possible, I was wondering if I could use the effects of one magnet to speed up the reversal of another. When I shutoff magnet 1,1; does not collapsing a magnet field cause a high voltage in the coil. I am thinking along the line of how a automobile coil generates the high voltage for the spark plug. Would it be possible that when I shutoff coil 1,1; I would get a voltage spike and I could use that voltage spike to say reverse coil 2,3. I could do then do the same and take the voltage spike from shutting off 2,3 and use that to increase the speed that I reverse coil 4,1; etc. I know there is going to be issues of timing and logic sequencing, but is this possible? And if it is possible and there is a slight time difference, could the energy from the voltage spike be momentarily held in a capacitor?

 

It may be too much to ask what kind of work you plan for the magnets, so consider this: You can flip a magnet end for end (north for south) using a coil. The magnet may be a 1 foot long bar with a width of 2 inches and a thickness of 1 inch.

OR you can flip a magnet end for end (north for south) using a coil. The magnet may be a 100 mm long bar with a width of 20 mm and a thickness of 10 mm.

The former would require significantly more energy than the smaller magnet.

My point is whatever work you are trying to accomplish will dictate the power required to accomplish it. From what I'm reading here it's not sounding like a very worth while endeavor. Since you want air core coils you must want a really really small item (whatever it may be) that is magnetically polarized to be able to flip over. I recall seeing indicators on electronic equipment in the forward radio rack of a DC 10 jet liner. These indicators were simply magnets, one end colored red the other colored yellow. A small current was used to flip the indicator to indicate some condition, be it "ON" or "OFF" or some other point of data. Once flipped the current could be shut off and the magnetic indicator would hold its position simply due to the magnetic attraction to the iron core of the controlling coil. For the life of me I can't imagine what you'd want to flip 300 times per second. The human eye can detect changes at a rate of about 28 cycles per second. 300 times per second - what are you trying to build? A new sort of TV? Or monitor? With 1 inch air coils I can't imagine anything smaller than a megatron at a ball game.

Point I want to make is that to do what you want is going to take significant amounts of energy. Personally I wish you success. I also wish I had the skills you're looking for. But I don't. Best I can muster is basic stuff.

 

I simulated 2 circuits for coil 10mH, 24Ohm, 1A feeding.
One is conventional, result on diagram 1.
Second is enhanced, result on diagram 2.
Green line - control signal, red line - current through coil and magnetic field.
Is it enough?
Diagram 1:

Diagram 2:

 

Note Technical specification error.

Sorry guys but I made an error on the specifications. I was trying to convert rpms to the more electronic friendly units of Hz and made a units conversion error. The repetitive rate of the coils should have been 5 Hz.

Good thing I was not trying to land a rover on Mars.

 

Good thing I was not trying to land a rover on Mars.

Do not know, how about Mars, but now we can change current in coil linearly, with speed 100,000 A/s (see diagram below).
By the way, Tesla, 124 years ago, invents "Coil for electro-magnets". That coil have not self-induction at all, therefore it is very good for fast working electromagnets (see PDF below).

 

I did this on a forum many years ago and it worked out great. I own a small business and I am looking for a skilled electronics person who is interested in partnering on a lucrative project. The ideal person would have to be capable of designing and prototyping a microprocessor, with user interface; that is capable of powering a 6x6 array of electromagnets. You must be able to develop the circuit to drive the electromagnets (probably using op amps) and then interface the circuit to the microcontroller. The magnets will need to be individually turned on, have their polarity reversed, and then be turned off with microsecond timing and driven by the microprocessor at a max rate of about 300Hz. The technical challenge as I see it is to be able to rapidly energize the magnet field, and then instantaneously reverse the field to negative full power polarity.

Currently I have created a computer simulation assuming ideal electronic performance and so far the simulation shows the project has a large margin of success. The plan is to 1) create a small scale unit of 3-4 electromagnets in order to obtain real world test data. 2) Use this test data to benchmark the simulation and then rerun the fullscale model to insure that a finish unit will work, 3) once a final design is determined, fabricate a prototype unit to solicit both government and private funding for full scale development and production. I expect that instantaneous polarity reversal will not be achievable, but once I can get some test data we can them use the simulation model to determine if there is a workable solution within the real world limits.

The potential for this project is large. Conservatively I would estimate 7-8 figures annually when we are in production. The product would be like a printer in that it will have a base unit and consumables (understand, it is not a printer). Anyone using the unit ($2000) would be consuming the consumable components at a rate of about $500 - $1000 per year. This is similar to what consumers are spending on out-dated items they are currently using so there is market history showing consumers are willing to pay these costs. This will be a huge leap forward in technology for this product line and consumers would be willing to pay for it. The project is unique enough that we will have patent protection on the base unit as well as the consumables, so there will be no competition. The market itself is large. There is potential for tens of thousands of units in the government sector, and hundreds of thousands of units in the commercial/private section.

The person I am looking for must be able to handle all of the electronic aspects previously discussed. I am looking for a hands-on person. The person also needs to currently have a fulltime job because in the initial stage this will not be a funded effort. If we get past the prototype stage and get development money, then the person will need to permanently come on board full time. My goal is to establish a company to be the only one producing this project. We will produce the base unit as well as set up an automated production line to produce the consumable items. I am looking for someone located in the Los Angeles, Orange County area so we can have personal contact. I have a small shop with cnc lathe and mills that will allow us to make all the prototype hardware. I do have some limited electronic equipment such as programmable power supplies, function generators, and digital oscilloscope to support the project. I also have data acquisition units and other specialized equipment that will be needed for testing. Ideally my plan would be to relocate the company prior to going into full scale production to a more business friendly state like Utah, Arizona, Oregon or whatever. I would what a small population area were we could get large acreage for person homes, large acreage for a plant with test facility, and not have to deal with crowded city life. Of course we will need to be civilized enough to have good internet and local shipping/receiving for raw components. Snow for a month or so a year would be fine, but I am looking to be able to run a highly profitable company, but in a small town environment.

I am 61, so I am not opposed to an older partner, but I am looking for a hands-on person, not someone who could only direct someone else to do the work. You will get dirty, but I will guarantee you will have fun. Personal compatibility will be important since I am look at this being a long term partnership starting with the proof of principle stage and finishing with running a profitable company. I am also not looking for someone to get the company started and then leave, so there will be contract clauses which will make it unprofitable for a partner to sell off his share. I do not want to get saddled with some fool at a later date that I do not have the final choice on working with. My plan would be to develop the product, get the company up and running, and eventually turn control over to my son who is currently studying computer engineering.I would like a partner who has similar life goals.

PM me if you are interested and tell me about your electronics background and experience, especially any work you have done using op-amps to drive a magnet field. This could be work with electromagnets themselves, or work with electronic fields in stepper motors or linear motor design. For the right person, I can meet you at your place to discuss things further after the proper Non disclosure and non-compete agreements are signed.

Hello,

The key piece of information is missing, and that is what do the 36 electromagnets actually have to do?
This dictates the strength of the electromagnets and therefore there size and therefore their switching speed and therefore the field rise and fall times.

The electromagnet sizes are restricted mostly by the volume of the region (how big they can be) and this limits the wire size and the wire size limits the current and/or duty cycle and the current dictates the voltage and the wire insulation limits the top voltage.
So many of the operating points are limited but it starts out by knowing the volume of space available for each electromagnet.

A similar situation can be found in stepper motors. You will notice that the stronger the torque, the bigger the motor.

 

RE: jwsigler
If You still are interested, probably me and/or my workplace may be interested to solve Your problem.
I am researcher at Atomic physics and Spectrometry Institute of Latvia University, Riga, European Union.
Our experience and technological possibilities allow to produce a small to medium large series of pcb, even SMD sized. Most of all the experiment result measurers we have for free (for example, my 4 channel oscilloscope sweeps up to 2,4 GHz at the need). I am physicist with specialization in RF and power electronics design and (of course) ARMs, vacuum and ion-beam technologies, my close mate is semi-genial ARM programmer, the neighbours institute where some friends are still working are those what first in the history realized the famous GeoDinamo experiment (read about it at Wikipedia) and EIMAO transport principle (there too) - so they are very excellent in magnetic problems and we always may ask them to help.
I am a product of 1959, speak in 7 languages, and have rather wide experience to collaborate with "foggy" projects.
So, dont hesitate to write me to .... or Facebook
University has a support program for small entrepreneurs - if entrepreneur comes with 5...50 thousands for solving a certain task defined by him, then University pays the identical money, and we may work together. So the expenses may be diminished twice-fold.

MOD: email deleted in order to protect your privacy from spamming.
E

And how, dear Mod, the author will send me a message now, huh??
If I print here my address, it means it is spam-proof enough and cannot be hacked without of minimum FBI and NASA capacities put together. And have a rather powerful artificial intelligence driven spam-filter. That is a biggest national server, stronger than Google or Yahoo mail systems in security meaning (to differ from US we are living territory next to russia government fed hacker farms, so to be bulletproof is essence to our survive).

P.S. Okay, I sent him it privately. Do nothing with this.
JWSigler: If You dont see my mail in Your private box, tick me here, I shall repeat.

 

By the way, any particular H for producing the B may be caused by a fixed Amper*turns. It means You may wind the 1 turn with 1000 Amps or wind a 1000 turns with a 1 Amp. But between those both stays difference in the inductance a n^2=1000 000 fold. Your aim ought be to wind such inductance what allows push the coil in resonance of tau=1 usec, or 4 MHz. You have even a chance that 5...10 turns be not too much. Thus calculate a wire diam and voila!.

 

RE:""2) Generating rapidly changing magnetic fields will create EMI. How will that be suppressed?""
The average distance where field You mentioned decreases at least tenfold is 1,5...3 diameters of coil. Thus, after this distance the magnetic ecrane will not cause a large power loss.

 

RE:""Red line - voltage, green line - current.""
To get result in non-sinus (semi-meandric) form You may use a high voltage source with constant current regime. The 4 MHz is just slow signal for most of igbt and hexfets even 100++ MHz. Thus to find a 1200 V transistor with some 20...100...1000 rated Amps is not impossible. And if magnetic field is product of current instead of voltage, then 1200V for sure very fast will beat out the "wrong" current off the coil. How fast? See here:

V=L*di/dt means that for example 100 Amp 1 usec 10 uH create a 1 kilovolt. So this idea is not so bad.
If vice versa, I mean using a resonant sign-change system, for example my elaborated 100 MHz 500W oscillator get 20 Amp into 4 turns with 46...80 MHz and everything works cheap and well even without of water cooling, but 2...4 kV there is persistent.

It would be more easy to calculate anything if to know how much kilograms You expect from what area in the magnet. Normally at maximum permitted B for good silicon steel one may hope to get until 10 kilograms per cm2 in no-air-gap regime.

 

RE:""The thought was that if we use any form of metallic core, the would hinder the time required to reverse the magnetic field polarity""
Not always. The ferrites may serve up to 1...5...10 MHz. One such extraordinary cheap from India I was bought an Europallet, so I use it in many SMPS constructions so I know it is capable for 3 MHz at 0,36 Teslas and gives a mju relative about 2200-2600. But it is rather sensitive about temperature and mechanically very brittle. Air core is generally good idea, more over, it has no limitations of B(max). Theoretically (in no connection with real dimensions) even thousand million Teslas one may get in air-core coil, if it is large enough and current density as well the cooling is hard enough.
Yet plastic core makes me suspicious, I had seen too much melted forming carcasses of coils. Them all was been thermoplastics. Better think about teflon, glass-textollite, paper, getinax, epoxide, glass, wood, and many more materials what are relatively heat resistant. The good wire can stand up to 200++ (C), but thermoplastics only 60(C).

 

RE:""Using coil with silver moving part may solve problem""
Sure NO!!
In this meaning I have ate the pounds of salt, I had made a silver coating etc etc, but the slogan that silver leads current better than copper IS WRONG!!!! Because at for example 100 MHz the Foucault depth is ca 3 microns. When Oxide layer is ca 5 microns. Therefore all the current is flowing at the OXIDE layer but not by metal. And silver oxide indeed has a better lead than copper oxide, with demanding it had been mechanically compacted. Soviet militarists did it processed after silvering in the steel-ball drum, and THEN silver-coated wires indeed are better as non-silvered. But if we speak of any "normal" methods of chemical, electrochemical, vacuum sputtered etc coatings, them ALL has serious problem of porosity, what creates a current PATH many-fold longer as geometric path between wire entrance and exit. Therefore all wires I made silvered in the tests shown many times worse Q-factor than non-silvered. Actually, one of best cheap-end method is just the lack (any suitable paint) as it saves the wire against oxygen and we don`t have to try get more.

 

RE:""Would it be possible that when I shutoff coil 1,1; I would get a voltage spike and I could use that voltage spike to say reverse coil 2,3""
Bright idea but I see no much possibilities to realize. The large power transformers at RF is the hard core hardcore. I mean very sophysticated and difficult, and expensive. Simpler and less headaches is not to be too greedy about energocompany income plan, and spend frest energy portion to each next coil. Them need to sell their energy to someone .

 

RE:""The electromagnet sizes are restricted mostly by the volume of the region""
However in case of few turn very large amperage coil the wire may happen with inner hole, I mean pipe, filled with aqua distillatum, with "electronic fluid" in case of microwaves, or even LN2. At least the simple water allows (if we not speak about 100 MHz) to get some 25 A/mm2 from 3/0,6 mm fridge expansion pipe and near to 100 A/mm2 from 6---10 mm santech copper-pipes. In contrast, the "normal" winding wire permit 3,5 A/mm2 in long run and 5 in repeatedly-short run.

 

RE:""Good thing I was not trying to land a rover on Mars""

We disputed with some mates here what Your Project MAY be. It ought be a Relsotron - device what concept was elaborated in 70-ies but still there are large difficulties about technical realization. Device is mounted in high mountain, where at 4 km altitude the air friction is far less than here at sea level, so the magnets are accelerating the lightweight space satellite like 0,5-1 kg Cubesat in very cheap and ecologic way. We have near the place where they produce a Cubesats, and national Astronomy Institute with its both Observatories is our best mates so we meet every single week. If I guessed right, that is great project indeed.