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## Gravity powered devices => Gravity powered devices => Topic started by: nathanj99 on March 16, 2015, 11:16:33 PM

Title: Measuring Amps on output coils
Post by: nathanj99 on March 16, 2015, 11:16:33 PM
Hi

I have built a wheel with 16 magnets around it much like the bedini SG. I put a coil on the bottom with no other electronic components just to see if I could get anything from the coil. I have connected my mulitimeter to the coil. When i spin the wheel by hand I may get about 10 milliamps but it is not constant. However when i spin the wheel fast I get no reading at all! Only when the wheel is moving slowly can i get about 30 miliamps. Can someone explain what I am doing wrong. Once the wheel just about stops turning the wheel will start to speed up again. I guess this is the energy in the coil doing this?

I am on a very steep learning curve, so would appreciate any advice.

thanks

Nath
Title: Re: Measuring Amps on output coils
Post by: FatBird on March 16, 2015, 11:22:11 PM
How many turns on the coil, & what gauge wire are you using?

Can you post a picture of it?
.
Title: Re: Measuring Amps on output coils
Post by: mscoffman on March 16, 2015, 11:36:30 PM
Maybe, coil wires and magnetic flux lines are not cutting each other. Show diagram.
Title: Re: Measuring Amps on output coils
Post by: burnit0017 on March 16, 2015, 11:44:01 PM
Hi, what is the wire size and number of turns on the coil?
Title: Re: Measuring Amps on output coils
Post by: gyulasun on March 17, 2015, 12:25:19 AM
Hi Nath,

Perhaps your digital multimeter is not able to show the higher than 50 or 60 Hz AC current? just guessing and you could check this by using a full wave diode bridge to rectify the AC voltage and use your meter in DC volt range across the diode bridge output where you also attach some hundred microFarad puffer capacitor for some filtering too?
If this sounds double dutch to you just search the web for full wave rectifier circuit with a puffer capacitor and you will be ok.

Gyula
Title: Re: Measuring Amps on output coils
Post by: nathanj99 on March 17, 2015, 11:13:46 AM
Thanks everyone.

I will post details of my build later. Had to go to flipping work! I had another attempt this morning and I did start getting some readings. Although the numbers were jumping all over the place! I guess I need a analogue amp meter? I do seem to get higher amps (10mAmps) when the wheel is slow. If I speed it up I get around 1 mAmp. But it could just be down to the meter. Would the collapsing emf mess up the value shown on the dmm? Is there a better way to measure the amps? I had a look at capacitors but as yet have no idea what size I need.

Nath
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 17, 2015, 11:24:48 AM
You should get one positive and one negative pulse from each passing magnet.  If your coil does not have a load, then you've got a basic generator and the peak voltage across the coil is determined by the number of turns, the strength of the magnets, the gap and the speed of the wheel.  If you pulse current from a battery or a power supply through the coil, and you don't do something to clamp the coil, or the signal through the meter, then you will get a big BEMF spike each time you interrupt the current.

Generally speaking, you will have an easier time if you use a shunt resistor for the current measurement.  Then you can insert any kind of needed filtering and/or protection between the current sense resistor and the DMM input.  It will also let you keep the wiring loops as small and tight in the circuit itself, which is important for pulse circuits.
Title: Re: Measuring Amps on output coils
Post by: sm0ky2 on March 17, 2015, 12:15:18 PM
Thanks everyone.

I will post details of my build later. Had to go to flipping work! I had another attempt this morning and I did start getting some readings. Although the numbers were jumping all over the place! I guess I need a analogue amp meter? I do seem to get higher amps (10mAmps) when the wheel is slow. If I speed it up I get around 1 mAmp. But it could just be down to the meter. Would the collapsing emf mess up the value shown on the dmm? Is there a better way to measure the amps? I had a look at capacitors but as yet have no idea what size I need.

Nath

Hi Nathan,

When you generate electricity in this manner, alternating north and south poles, the current will come out as an A/C wave-form.
+ then -, respectively.
So you will need an A/C meter or a scope to get any kind of accurate reading.
some quick-response DC meters may show the result, but it flashes back and forth so its hard to see the read out.

another option may be to run the coil leads through a square-wave or full-wave rectifier
then you have a DC current to measure. This will be minus the losses through the diodes, of course.
which can also be measured with your DC meter then add the values up

hope this helps
Title: Re: Measuring Amps on output coils
Post by: nathanj99 on March 18, 2015, 09:36:50 AM
You should get one positive and one negative pulse from each passing magnet.  If your coil does not have a load, then you've got a basic generator and the peak voltage across the coil is determined by the number of turns, the strength of the magnets, the gap and the speed of the wheel.  If you pulse current from a battery or a power supply through the coil, and you don't do something to clamp the coil, or the signal through the meter, then you will get a big BEMF spike each time you interrupt the current.

Generally speaking, you will have an easier time if you use a shunt resistor for the current measurement.  Then you can insert any kind of needed filtering and/or protection between the current sense resistor and the DMM input.  It will also let you keep the wiring loops as small and tight in the circuit itself, which is important for pulse circuits.

Could you explain to me why i get one positive and one negative pulse from each magnet please. What sort of shunt resister should i use?

So what i have at the moment it a 90cm wheel with 16 magnets around it. I was experimenting with a coil sat underneath the wheel. The distance between coil and magnets is about 3-5mm. I was messing about with a coil of 1.00mm wire, 2.2 ohms, 1066 turns. I have a coil of bifilar which i have not yet put the core in. That is 0.45mm 1619 turns.

Nath
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 18, 2015, 12:51:27 PM
Could you explain to me why i get one positive and one negative pulse from each magnet please.
Because as the magnet approaches the coil, the flux will increase quickly in one direction, reach a maximum rate of change, and then the rate of change will fall to zero very close to where the magnet makes its closest approach.  That makes a voltage pulse in one direction.  As the magnet moves from its closest approach the reverse process occurs and a complementary shaped voltage pulse forms in both time and amplitude.
Quote

What sort of shunt resister should i use?
Use a resistor that has a low inductive impedance compared to the resistance at the signal frequencies you are measuring.  Your basic frequency with 16 magnets will be:  rpm*0.267.  I don't know how sharp your rise times will be, so let's just take a gross stab and say that they are  about 1/350th the magnet to magnet interval.  So, the signal frequency content will be significant up to around RPM*0.267*350/0.35 ~= rpm*270.  I am going to venture that you are staying under 2000rpm, so I expect the frequency content will be mostly under 500kHz.  You would like jwL @ 500kHz < 0.1*RCSR.  So, a tabulation:

L < 0.314uH*R

R = 100 Ohms, L < 31uH, 5W resistor safely handles 170mA rms
R = 10 Ohms, L < 3.1uH, 5W resistor safely handles 0.5A rms
R = 1 Ohm, L < 310nH, 5W resistor safely handles 1.7A rms
R = 0.1 Ohm, L < 31nH, 5W resistor safely handles 5A rms

These resistors from Digikey have practical inductances down around 3nH, and they are affordable, handle a decent amount of power, and are 1%:  http://www.digikey.com/product-search/en?pv1=1323&pv1=1025&pv1=1028&pv1=103&pv1=2358&FV=fff40001%2Cfff80482%2C1c0002&k=wne&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25.

You should solder sense wires to each side of the resistor, right at the body.  You can tightly twist those wires together and take them away to your oscilloscope probe, or DMM.
Quote

So what i have at the moment it a 90cm wheel with 16 magnets around it. I was experimenting with a coil sat underneath the wheel. The distance between coil and magnets is about 3-5mm. I was messing about with a coil of 1.00mm wire, 2.2 ohms, 1066 turns. I have a coil of bifilar which i have not yet put the core in. That is 0.45mm 1619 turns.

Nath
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 18, 2015, 07:09:11 PM
Hi

I have built a wheel with 16 magnets around it much like the bedini SG. I put a coil on the bottom with no other electronic components just to see if I could get anything from the coil. I have connected my mulitimeter to the coil. When i spin the wheel by hand I may get about 10 milliamps but it is not constant. However when i spin the wheel fast I get no reading at all! Only when the wheel is moving slowly can i get about 30 miliamps. Can someone explain what I am doing wrong. Once the wheel just about stops turning the wheel will start to speed up again. I guess this is the energy in the coil doing this?

I am on a very steep learning curve, so would appreciate any advice.

thanks

Nath
First advice: Provide all neccesary information.
Example of neccessary information:

Coil details -> Number of turns, coil hight/outer-inner diameter, wire gauge, inner resistance of the coil, iron core/air core
Distance between coil and magnets
Angular velocity of the magnets
Magnets orientation, assambly details.
Magnetic flux crossing through the coil measured in Gauss
Voltage readings over the coil.
Load details - whatever you use, bulb, resistor, short circuit. Provide resistance values.

An unloaded coil will not cause any current flow at all. You must load it. Also, you get AC out of the coil. Not DC. Check your instrument what setting you've choosen.

What's most interesting here, is the voltage x ampére product. I mean Watt or Joule pr./second - applies only on pure resistive loads. Ampére alone does not carry energy. Voltage alone does not carry energy.

Vidar

Title: Re: Measuring Amps on output coils
Post by: nathanj99 on March 18, 2015, 10:32:04 PM
Because as the magnet approaches the coil, the flux will increase quickly in one direction, reach a maximum rate of change, and then the rate of change will fall to zero very close to where the magnet makes its closest approach.  That makes a voltage pulse in one direction.  As the magnet moves from its closest approach the reverse process occurs and a complementary shaped voltage pulse forms in both time and amplitude.Use a resistor that has a low inductive impedance compared to the resistance at the signal frequencies you are measuring.  Your basic frequency with 16 magnets will be:  rpm*0.267.  I don't know how sharp your rise times will be, so let's just take a gross stab and say that they are  about 1/350th the magnet to magnet interval.  So, the signal frequency content will be significant up to around RPM*0.267*350/0.35 ~= rpm*270.  I am going to venture that you are staying under 2000rpm, so I expect the frequency content will be mostly under 500kHz.  You would like jwL @ 500kHz < 0.1*RCSR.  So, a tabulation:

L < 0.314uH*R

R = 100 Ohms, L < 31uH, 5W resistor safely handles 170mA rms
R = 10 Ohms, L < 3.1uH, 5W resistor safely handles 0.5A rms
R = 1 Ohm, L < 310nH, 5W resistor safely handles 1.7A rms
R = 0.1 Ohm, L < 31nH, 5W resistor safely handles 5A rms

These resistors from Digikey have practical inductances down around 3nH, and they are affordable, handle a decent amount of power, and are 1%:  http://www.digikey.com/product-search/en?pv1=1323&pv1=1025&pv1=1028&pv1=103&pv1=2358&FV=fff40001%2Cfff80482%2C1c0002&k=wne&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25.

You should solder sense wires to each side of the resistor, right at the body.  You can tightly twist those wires together and take them away to your oscilloscope probe, or DMM.

Wow thanks Mark. But seriously, that went way over my head. Maybe i should just quit at the woodwork stage :( . I just cannot get your equations and calculations. I dont really have much hope at this do i?

Nath
Title: Re: Measuring Amps on output coils
Post by: sm0ky2 on March 18, 2015, 10:56:59 PM
Ampére alone does not carry energy.
Vidar

Could you provide an example of where Ampere exists, without voltage?
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 22, 2015, 10:33:13 AM
Could you provide an example of where Ampere exists, without voltage?
In superconductors. Current flow has nothing to do with voltage.
In the oposite case, you can have voltage, but no current (Ampéres).
Normal conductors have loss due to resistance. This resistance will cause a voltage drop when current flows through it.
Therfor you might assume that you cannot have a current flow without applying voltage.

For example: You only need current to make a magnetic field.
Permanent magnets have this current going on on an atomic level, but there is not voltage involved.
Also the reason why permanent magnets cannot provide free energy, because the product of current and voltage is zero.

Vidar

Title: Re: Measuring Amps on output coils
Post by: tinman on March 22, 2015, 12:12:09 PM
In superconductors. Current flow has nothing to do with voltage.
In the oposite case, you can have voltage, but no current (Ampéres).
Normal conductors have loss due to resistance. This resistance will cause a voltage drop when current flows through it.
Therfor you might assume that you cannot have a current flow without applying voltage.

For example: You only need current to make a magnetic field.
Permanent magnets have this current going on on an atomic level, but there is not voltage involved.
Also the reason why permanent magnets cannot provide free energy, because the product of current and voltage is zero.

Vidar
Current flow has everything to do with voltage. If you have no potential difference,then current will not flow. The voltage differential may be very small,but there has to be one. I must also ask how current flows in ferrite magnet's,as the ferrite is non conductive,and even if it were,you would have nothing but a dead short. A dead short with current flowing through it means extensive heat-->PMs do not get hot sitting on the bench.
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 22, 2015, 12:31:41 PM
Current flow has everything to do with voltage. If you have no potential difference,then current will not flow. The voltage differential may be very small,but there has to be one. I must also ask how current flows in ferrite magnet's,as the ferrite is non conductive,and even if it were,you would have nothing but a dead short. A dead short with current flowing through it means extensive heat-->PMs do not get hot sitting on the bench.
You're right if you consider the energy source as the voltage drop. The voltage drop over the super conductor is zero, but current is still flowing.
Inducing current flow through a super conductor using a passing magnet, there is no voltage present anywhere but the current is flowing still.

The point is that Ampere or Voltage alone cannot be considered as energy. Only the product of them are energy.

Vidar
Title: Re: Measuring Amps on output coils
Post by: tinman on March 22, 2015, 02:21:14 PM
You're right if you consider the energy source as the voltage drop. The voltage drop over the super conductor is zero, but current is still flowing.

The point is that Ampere or Voltage alone cannot be considered as energy. Only the product of them are energy.

Vidar
Quote
Inducing current flow through a super conductor using a passing magnet, there is no voltage present anywhere but the current is flowing still.
Where is it flowing?. In order to have a flow,it must have direction. So in a super conductor,which direction is this flow of current?. The same question would apply to the PM. We often use waterand pipes to explain current flow through a wire. Is a super conductor represented by a bucket full of water,or a looped pipe that is full of water?. If so,in order for the water !current! to flow,there must be a differential in pressure !voltage!. I see no way current can flow in a super conductor,a PM or any other circuit without a potential difference in voltage. It is assumed that a super conductor can produce a magnetic field,but that is not the case. It becomes diamagnetic,as a super conductor will repell both fields of a magnet. So the magnetic field seen in a super conductor is a mirror of the magnetic field that it is exposed to. Magnetic fields are actually excluded from super conductors-this is called the Meissner effect. You may be confused to what they call the induced super currents,which are the mirror field of the PM above the super conductive surface.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 22, 2015, 04:07:20 PM
Where is it flowing?. In order to have a flow,it must have direction. So in a super conductor,which direction is this flow of current?. The same question would apply to the PM. We often use waterand pipes to explain current flow through a wire. Is a super conductor represented by a bucket full of water,or a looped pipe that is full of water?. If so,in order for the water !current! to flow,there must be a differential in pressure !voltage!. I see no way current can flow in a super conductor,a PM or any other circuit without a potential difference in voltage. It is assumed that a super conductor can produce a magnetic field,but that is not the case. It becomes diamagnetic,as a super conductor will repell both fields of a magnet. So the magnetic field seen in a super conductor is a mirror of the magnetic field that it is exposed to. Magnetic fields are actually excluded from super conductors-this is called the Meissner effect. You may be confused to what they call the induced super currents,which are the mirror field of the PM above the super conductive surface.
It takes energy to initially induce the current.  The current is induced in a super conductor just as it is in an ordinary coil winding.  An induced voltage builds up current in the coil against the inductance of the loop.  Thus work is performed to transfer energy into the magnetic field surrounding the super conductor.
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 22, 2015, 05:11:20 PM
Where is it flowing?. In order to have a flow,it must have direction. So in a super conductor,which direction is this flow of current?. The same question would apply to the PM. We often use waterand pipes to explain current flow through a wire. Is a super conductor represented by a bucket full of water,or a looped pipe that is full of water?. If so,in order for the water !current! to flow,there must be a differential in pressure !voltage!. I see no way current can flow in a super conductor,a PM or any other circuit without a potential difference in voltage. It is assumed that a super conductor can produce a magnetic field,but that is not the case. It becomes diamagnetic,as a super conductor will repell both fields of a magnet. So the magnetic field seen in a super conductor is a mirror of the magnetic field that it is exposed to. Magnetic fields are actually excluded from super conductors-this is called the Meissner effect. You may be confused to what they call the induced super currents,which are the mirror field of the PM above the super conductive surface.
If we take water - good you brought it up. It is easier to understand.

The bucket: Waterpressure at the bottom will cause the flow from the hose connected to the buckets bottom. Voltage is pressure. Ampere is the flow. Higher pressure, higher flowrate.

Superconductor: A hose is looped like a donut. Water does not "see" friction in the wall inside, and will continue to flow forever in a loop when it has started.

Have you ever tried the experiment at school when you cool down an object that becoms super conductive when cooled down?
Placing a magnet on top of it will cause the magnet to hover.
When you approach the magnet, eddy currents are starting to build up in the superconductor and keep flowing - making an equal and oposite magnetic field. This current is continuing to flow "forever" as long the object is superconductive, but no voltage is applied - only the "pressure" from the magnet you put over it. No matter how the magnet will move (up, down or sideways) the superconductor is "charged" by eddy currents that all the time reposition the magnetic field respectively to the magnets position. That is why the magnet is hovering at the same place and not fall off to the sides. If you press the magnet further down, more eddy curent builds up, also the magnetic field from the superconductor increase, and is stronger than the magnets weight. The magnt returns back to the same position again - balancing between its weight and the magnetic force from the superconductor trying to push it away.

Vidar
Title: Re: Measuring Amps on output coils
Post by: tinman on March 22, 2015, 08:33:38 PM
It takes energy to initially induce the current.  The current is induced in a super conductor just as it is in an ordinary coil winding.  An induced voltage builds up current in the coil against the inductance of the loop.
Quote
Thus work is performed to transfer energy into the magnetic field surrounding the super conductor.
There is no magnetic field surrounding a super conductor.
Title: Re: Measuring Amps on output coils
Post by: MileHigh on March 22, 2015, 08:39:20 PM
There is no magnetic field surrounding a super conductor.

If I recall correctly there is no magnetic field inside a superconductor.  But of course there is a magnetic field outside a superconductor.

Put a "black box" around the superconducting wire.  So what do you have?  All that you know is that current is flowing through the black box.  Therefore outside the black box there is a magnetic field.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 22, 2015, 10:44:11 PM
There is no magnetic field surrounding a super conductor.
That's just wrong.  The Meissner Effect causes a super conductor to reject all external magnetic fields from penetrating inside the superconductor.  The fields inside and outside are very real and very useful, or at least entertaining.  Here is a very fun instructive demonstration by the Royal Society.  https://www.youtube.com/watch?v=zPqEEZa2Gis  Here is another fun demo:  https://www.youtube.com/watch?v=VyOtIsnG71U.
Title: Re: Measuring Amps on output coils
Post by: TinselKoala on March 22, 2015, 11:24:32 PM
And here's my demo of an interesting effect using a superconductor and a magnet:

http://www.youtube.com/watch?v=JRby1Wilv-Q
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 22, 2015, 11:36:31 PM
And here's my demo of an interesting effect using a superconductor and a magnet:

http://www.youtube.com/watch?v=JRby1Wilv-Q
I always enjoyed that demonstration.
Title: Re: Measuring Amps on output coils
Post by: TinselKoala on March 22, 2015, 11:59:49 PM
I always enjoyed that demonstration.
Yes, it's a good one and leads-out much thought and speculation.

One question that immediately arises is this: Does the magnet always wind up rotating in the same direction or sense?
No... it does not. It can rotate in either direction once it gets started.

I have also done the experiment using a larger disc magnet, about the size and shape of a US quarter-dollar coin, completely
wrapped in copper foil. My thinking was that this should help to equalize any thermal gradient across the magnet. It still rotates.

The superconductor is a YBCO type, melt-textured and sintered, prepared according to formulae and directions from Eugene Podkletnov.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 23, 2015, 12:56:30 AM
Yes, it's a good one and leads-out much thought and speculation.

One question that immediately arises is this: Does the magnet always wind up rotating in the same direction or sense?
No... it does not. It can rotate in either direction once it gets started.

I have also done the experiment using a larger disc magnet, about the size and shape of a US quarter-dollar coin, completely
wrapped in copper foil. My thinking was that this should help to equalize any thermal gradient across the magnet. It still rotates.

The superconductor is a YBCO type, melt-textured and sintered, prepared according to formulae and directions from Eugene Podkletnov.
It is a brain teaser.  I am inclined to think that it is thermal gradients changing the magnet force top to bottom that drive the thing.  Foil is so-so as a thermal conductor because of the aspect ratio.  If you were to come up with copper or aluminum cup halves with reasonably thick walls to place the disc magnet in, then I think you would see the oscillations damp.  Unfortunately, part of that would be due to eddy current braking.

An alternative experiment might be to cover the vessel placing the pressure vent holes off to the sides so that gas currents and temperature gradients are mostly lateral.  Thinking off the cuff a pair of concentric plastic domes with a barrier above the vent holes should really reduce both gradients in the region of the magnet.
Title: Re: Measuring Amps on output coils
Post by: tinman on March 23, 2015, 03:22:55 AM
That's just wrong.  The Meissner Effect causes a super conductor to reject all external magnetic fields from penetrating inside the superconductor.  The fields inside and outside are very real and very useful, or at least entertaining.  Here is a very fun instructive demonstration by the Royal Society.  https://www.youtube.com/watch?v=zPqEEZa2Gis  Here is another fun demo:  https://www.youtube.com/watch?v=VyOtIsnG71U.
The magnetic field is introduced/induced by the PM, a super conductor dose not have a magnetic field unless one is introduced/induced by a PM or electromagnet. Cool the super conductor down without introducing a magnetic field, and try to get a magnetic material to stick to it. You see the super conductor is held so far off the track wether upsidedown or on top of the track. The same effect can be done with standard PMs
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 23, 2015, 03:33:29 AM
The magnetic field is introduced/induced by the PM, a super conductor dose not have a magnetic field unless one is introduced/induced by a PM or electromagnet. Cool the super conductor down without introducing a magnetic field, and try to get a magnetic material to stick to it. You see the super conductor is held so far off the track wether upsidedown or on top of the track. The same effect can be done with standard PMs
The magnetic field that we are concerned with is the one poled into the superconductor.  Each of those demonstratins does that.  Try and get a copper bar to float underneath strong magnets.  It will slowly fall a short distance and then drop very fast.
Title: Re: Measuring Amps on output coils
Post by: tinman on March 23, 2015, 05:18:30 AM
The magnetic field that we are concerned with is the one poled into the superconductor.  Each of those demonstratins does that.  Try and get a copper bar to float underneath strong magnets.  It will slowly fall a short distance and then drop very fast.
And once this field is poled into the super cooled material , you believe a current is now flowing through that material?-without a voltage potential?
As I said, the same effect can be done with magnets arranged in a particular fashion.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 23, 2015, 05:45:25 AM
And once this field is poled into the super cooled material , you believe a current is now flowing through that material?-without a voltage potential?
As I said, the same effect can be done with magnets arranged in a particular fashion.
Superconductors have the unique ability to circulate current without loss:  No sustaining voltage is required to maintain the current.
Title: Re: Measuring Amps on output coils
Post by: TinselKoala on March 23, 2015, 08:44:06 AM
Sigh. WIKI is your friend.

Quote
Superconducting magnets have a number of advantages over resistive (http://en.wikipedia.org/wiki/Electrical_resistance) electromagnets. They can generate magnetic fields that are up to ten times stronger than those generated by ordinary ferromagnetic-core electromagnets (http://en.wikipedia.org/wiki/Electromagnet), which are limited to fields of around 2 T. The field is generally more stable, resulting in less noisy measurements. They can be smaller, and the area at the center of the magnet where the field is created is empty rather than being occupied by an iron core. Most importantly, for large magnets they can consume much less power. In the persistent state (above), the only power the magnet consumes is that needed for any refrigeration equipment to preserve the cryogenic temperature. Higher fields, however can be achieved with special cooled resistive electromagnets (http://en.wikipedia.org/wiki/Bitter_electromagnet), as superconducting coils will enter the normal (non-superconducting) state (see quench, above) at high fields.
Superconducting magnets are widely used in MRI (http://en.wikipedia.org/wiki/MRI) machines, NMR (http://en.wikipedia.org/wiki/Nuclear_magnetic_resonance) equipment, mass spectrometers (http://en.wikipedia.org/wiki/Mass_spectrometer), magnetic separation processes, and particle accelerators (http://en.wikipedia.org/wiki/Particle_accelerator).
One of the most challenging use of SC magnets is in the LHC (http://en.wikipedia.org/wiki/LHC) particle accelerator (http://en.wikipedia.org/wiki/Particle_accelerator).[7] The niobium-titanium (http://en.wikipedia.org/wiki/Niobium-titanium) (Nb-Ti) magnets operate at 1.9 K to allow them to run safely at 8.3 T. Each magnet stores 7 MJ. In total the magnets store 10.4 GJ. Once or twice a day, as the protons are accelerated from 450 GeV to 7 TeV, the field of the superconducting bending magnets will be increased from 0.54 T to 8.3 T.
The central solenoid and toroidal field superconducting magnets designed for the ITER (http://en.wikipedia.org/wiki/ITER) fusion reactor use niobium-tin (http://en.wikipedia.org/wiki/Niobium-tin) (Nb3Sn) as a superconductor. The Central Solenoid coil will carry 46 kA and produce a field of 13.5 teslas. The 18 Toroidal Field coils at max field of 11.8 T will store 41 GJ (total?).[clarification needed] They have been tested at a record 80 kA. Other lower field ITER magnets (PF and CC) will use niobium-titanium (http://en.wikipedia.org/wiki/Niobium-titanium). Most of the ITER magnets will have their field varied many times per hour.
One high resolution mass spectrometer (http://en.wikipedia.org/wiki/Mass_spectrometer) is planned to use a 21 Tesla SC magnet.[8]

http://en.wikipedia.org/wiki/Superconducting_magnet
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 23, 2015, 09:05:49 AM
Yes, it's a good one and leads-out much thought and speculation.

One question that immediately arises is this: Does the magnet always wind up rotating in the same direction or sense?
No... it does not. It can rotate in either direction once it gets started.

I have also done the experiment using a larger disc magnet, about the size and shape of a US quarter-dollar coin, completely
wrapped in copper foil. My thinking was that this should help to equalize any thermal gradient across the magnet. It still rotates.

The superconductor is a YBCO type, melt-textured and sintered, prepared according to formulae and directions from Eugene Podkletnov.
I assume the coolest side of the magnet change location as it "wobbles" so in a way this magnet starts to rotate due to difference in temperature. Its a lag in the temp.change, always delayed, causing the phenomenon.

My guess.
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 23, 2015, 01:01:12 PM
Ref. post 31. The coolest side of the magnet are getting temporarily demagnetized. I wonder if this rotation would happen if you put styrofoam between the magnet and the liquid nitrogen - insolateing the magnet somehow...

Vidar.
Title: Re: Measuring Amps on output coils
Post by: Low-Q on March 23, 2015, 03:50:00 PM
Ref. post 31-32. Cooling a magnet makes it more magnetized. So this is a heat engine based on magnetism :-)
Title: Re: Measuring Amps on output coils
Post by: verpies on March 24, 2015, 03:23:52 PM
There is no magnetic field surrounding a super conductor.
Yes there is, if a superconductive ring was made superconductive (frozen) WHILE a non-zero external magnetic flux was penetrating it.
Such superconducting ring will generate the magnetic flux penetrating its hole even when the external flux source is removed.

This is called "flux freezing" and can be used to attract a soft ferrite to a superconducting ring - just like a magnet would.

P.S.
Conversely, when such superconductor is "frozen" with magnetic flux absent, then it will continue to exclude any external flux, should such appear in its vicinity.  In other words, a superconducting ring maintains the flux level, which existed in its hole when it was "frozen".
Title: Re: Measuring Amps on output coils
Post by: verpies on March 24, 2015, 03:36:16 PM
If I recall correctly there is no magnetic field inside a superconductor.
Leaving aside "flux pinning" inside type II superconductors, that concept gets a little murky when a superconducting ring is considered.  Does the hole in a superconducting ring constitute an "inside" or "outside" ?
Title: Re: Measuring Amps on output coils
Post by: verpies on March 24, 2015, 03:47:59 PM
And once this field is poled into the super cooled material , you believe a current is now flowing through that material?-without a voltage potential?
Yes and I find it very annoying when people try to apply voltage and EMF concepts to shorted coils - this is not necessary because coils are inherently current devices (while capacitors are voltage devices, btw).

Yes, you can do it, as long as a coil has some resistance, that keeps dissipating coil's energy (that's what Faraday's law is about) but it is like fitting a square peg into a round hole with shorted superconducting coils...
Title: Re: Measuring Amps on output coils
Post by: tinman on March 24, 2015, 10:17:17 PM
Yes and I find it very annoying when people try to apply voltage and EMF concepts to shorted coils - this is not necessary because coils are inherently current devices (while capacitors are voltage devices, btw).

Yes, you can do it, as long as a coil has some resistance, that keeps dissipating coil's energy (that's what Faraday's law is about) but it is like fitting a square peg into a round hole with shorted superconducting coils...
Although you believe a coil is a current device,the current/voltage value is dependant on resistance. The higher the resistance,the lower the current,and higher the voltage-disregarding the super conductor of course. The same applies to capacitors. Capacitors can deliver extreem currents across low resistive loads,while the voltage across that load may be low.

Now,what is the difference between a super conducting ring(that has only an internal magnetic field once a current is sent through it,and the good old room temperature PMH ?
Title: Re: Measuring Amps on output coils
Post by: verpies on March 25, 2015, 01:07:47 AM
Although you believe a coil is a current device,the current/voltage value is dependant on resistance.
An ideal inductor has no resistance.  Working in terms of voltage with inductors is only needed to account for their imperfections -  resistive "energy leaks".

Also, a natural state for an inductor is when it is shorted and a natural state for a capacitor is when it is opened.
With ideal components, there is no energy leakage out of them then.

When you do something unnatural for them, e.g. open an energized coil or short an energized capacitor, then all hell breaks loose.

Now,what is the difference between a super conducting ring (that has only an internal magnetic field once a current is sent through it) and the good old room temperature PMH ?
Do you mean this (https://www.youtube.com/watch?v=r9Kg69cQteg) by "PMH" ?
Title: Re: Measuring Amps on output coils
Post by: tinman on March 25, 2015, 02:35:46 AM
An ideal inductor has no resistance.  Working in terms of voltage with inductors is only needed to account for their imperfections -  resistive "energy leaks".

Also, a natural state for an inductor is when it is shorted and a natural state for a capacitor is when it is opened.
With ideal components, there is no energy leakage out of them then.

When you do something unnatural for them, e.g. open an energized coil or short an energized capacitor, then all hell breaks loose.
Do you mean this (https://www.youtube.com/watch?v=r9Kg69cQteg) by "PMH" ?
Yes-like in the video, although I see laserhacker was a little lost as to why he had to short the coil on the Ecore to get the effect, when the explanation is quite simple.
Title: Re: Measuring Amps on output coils
Post by: tinman on March 25, 2015, 02:47:54 AM
Yes-like in the video, although I see laserhacker was a little lost as to why he had to short the coil on the Ecore to get the effect, when the explanation is quite simple.
In fact, that video just showed you a continual current flow through a non superconductive coil.
Title: Re: Measuring Amps on output coils
Post by: verpies on March 25, 2015, 09:29:45 AM
.
Title: Re: Measuring Amps on output coils
Post by: verpies on March 25, 2015, 09:52:39 AM
Now,what is the difference between a super conducting ring(that has only an internal magnetic field once a current is sent through it,and the good old room temperature PMH ?
The PMH relies on the same effect as a tape recorder to store information - the remanent magnetization of high coercivity ferromagnetic material (...or not a very soft one).  Qualitatively this is no different than the attraction by a permanent magnet.

The difference between the attraction of a soft ferromagnetic keeper by an energized superconducting ring versus by a permanent magnet is that the flux through the superconducting ring always stays constant, while it does not stay constant in case of a permanent magnet  (that's why the LED flashes in this video (http://www.overunity.com/youtu.be/832qz3s1M-s?t=12m23s)).
The other difference is that the attraction of a superconducting ring can be "turned off" (by interrupting the electric current in it) while the attraction of a permanent magnet cannot be "turned off" (short of demagnetizing / destroying it, e.g. by exceeding its Curie temperature).

The other operational mode of PMH ( the one with the shorted coil and very soft ferrite) is devoid of magnetic remanence effects and differs from a superconducting ring only in magnitude of the L/R time constant.
If the PMH does not hold the keeper when the coil is opened or absent, but holds it indefinitely when that coil shorted (or longer that 5*L/R), then it is an anomaly.

There could be a brief discussion about the influence of dΦ/dt on the final level of remanent magnetization in the core, but it will not lead anywhere - been there, done that...

In fact, that video just showed you a continual current flow through a non superconductive coil.
Not a "continual current flow" - more like a LONG one...
Give me the inductance and resistance of that shorted coil and I will let you know whether that time was unusually long or not. ( t  >> 5*L/R ).
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 25, 2015, 10:26:39 AM
In fact, that video just showed you a continual current flow through a non superconductive coil.
Verpies is right:  The field weakens enough to cause the pieces to separate after a couple of seconds.  That tells us that the current decreases over time.  It does not sustain.
Title: Re: Measuring Amps on output coils
Post by: tinman on March 25, 2015, 05:32:09 PM

(short of demagnetizing / destroying it, e.g. by exceeding its Curie temperature).

The other operational mode of PMH ( the one with the shorted coil and very soft ferrite) is devoid of magnetic remanence effects and differs from a superconducting ring only in magnitude of the L/R time constant.

Quote
Not a "continual current flow" - more like a LONG one...
Yes-bad wording on my behalf.

Quote
The other difference is that the attraction of a superconducting ring can be "turned off" (by interrupting the electric current in it) while the attraction of a permanent magnet cannot be "turned off" (short of demagnetizing / destroying it, e.g. by exceeding its Curie temperature).
This is true some what.While it cant be switched off, an alnico's magnetic field can be flipped quite easly,and without much power to do so.

Quote
If the PMH does not hold the keeper when the coil is opened or absent, but holds it indefinitely when that coil shorted (or longer that 5*L/R), then it is an anomaly.
Do you know why the Ecore keepers will not stay together without the shorted coil?,the answer is quite interesting--odds and evens. ;)

Quote
There could be a brief discussion about the influence of dΦ/dt on the final level of remanent magnetization in the core, but it will not lead anywhere - been there, done that...
Give me the inductance and resistance of that shorted coil and I will let you know whether that time was unusually long or not. ( t  >> 5*L/R ).

The coil in that demonstration was not a good design. There is no need for two sepperate coil's. You need only one coil wound in a partiqular way. My PMH that was the same Ecore design(smaller Ecore),but with a coil wound this certain way,was able to maintain it's bonding for over 11 minutes. I believe a larger gauge wire would have seen this time increase,due to less resistance.

I really think there is something that can be had from the PMH.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 25, 2015, 06:19:30 PM
Yes-bad wording on my behalf.
This is true some what.While it cant be switched off, an alnico's magnetic field can be flipped quite easly,and without much power to do so.
Do you know why the Ecore keepers will not stay together without the shorted coil?,the answer is quite interesting--odds and evens. ;)
The ferrite material has a very low remnant magnetization.
Quote

The coil in that demonstration was not a good design. There is no need for two sepperate coil's. You need only one coil wound in a partiqular way. My PMH that was the same Ecore design(smaller Ecore),but with a coil wound this certain way,was able to maintain it's bonding for over 11 minutes. I believe a larger gauge wire would have seen this time increase,due to less resistance.
It is the ratio of resistance to inductance that matters.  It scales with the window area of the bobbin, AC and the fill factor, KFILL_FACTOR:

number of turns: n = KFILL_FACTOR*AC/AWIRE
L = K1*n2  = K1*KFILL_FACTOR2*AC2/AWIRE2
R = K2*n/AWIRE = K2*KFILL_FACTOR*AC/AWIRE2

L/R = K1/K2*KFILL_FACTOR*AC

You can increase L/R by using a cores with the same length per turn but larger winding area, IE a longer bobbin, using wire with thinner insulation as a proportion of the wire cross-section area, or by going with square wire instead of circular wire.  So, large gauge, square magnet wire is the best choice, followed by large guage, round magnet wire.  But it only improves a percent or two per wire gauge step.
Quote

I really think there is something that can be had from the PMH.
There is:  Stored energy actuators.  People have been building them for about 100 years that I know about.
Title: Re: Measuring Amps on output coils
Post by: tinman on March 26, 2015, 02:00:46 AM

Quote
The ferrite material has a very low remnant magnetization
.
No-thats not it. If you remove the center leg so as the core now has only one single loop,the two core halves will stay together for years. You need to look a little closer to the path that the magnetic currents can travel(if we can call them magnetic currents).

Remnant magnetism is also an incorrect term,as that is not what it is.

Remnant-1.a part or quantity that is left after the greater part has been used, removed, or destroyed.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 26, 2015, 05:29:45 AM
.
No-thats not it. If you remove the center leg so as the core now has only one single loop,the two core halves will stay together for years. You need to look a little closer to the path that the magnetic currents can travel(if we can call them magnetic currents).

Remnant magnetism is also an incorrect term,as that is not what it is.

Remnant-1.a part or quantity that is left after the greater part has been used, removed, or destroyed.
There is a field.  There is not a flow.  Low remanence material like ferrite will have very little force without a sustaining current.
Title: Re: Measuring Amps on output coils
Post by: tinman on March 26, 2015, 10:52:20 AM
Quote
There is a field.  There is not a flow.

I disagree.I (like verpies) have done many test over many hours with the PMH. If there is no flow,then why will a U core retain this magnetic field,while an E core of the same ferrite will not?(both without the coil shorted)

Quote
Low remanence material like ferrite will have very little force without a sustaining current.
Not what i found in my test. Useing a U core(ferrite),it takes the same force to sepperate the two halves of the core without current flowing through the coil as it dose with current still flowing through the coil that creates the field in the first place.
Is it the magnetic field that is creating the current flow through the coil,or is it the current flow through the coil that maintains the magnetic field?.
Title: Re: Measuring Amps on output coils
Post by: MarkE on March 26, 2015, 11:20:09 AM

I disagree.I (like verpies) have done many test over many hours with the PMH. If there is no flow,then why will a U core retain this magnetic field,while an E core of the same ferrite will not?(both without the coil shorted)
The flux distribution in the two shapes is different.  The mechanical force across a reluctance gap squares with the flux density.  An E-E combination reduces the flux density and therefore the mechanical force.
Quote

Not what i found in my test. Useing a U core(ferrite),it takes the same force to sepperate the two halves of the core without current flowing through the coil as it dose with current still flowing through the coil that creates the field in the first place.
That would only make sense to me if you had a considerable gap, which would also make the force weak.
Quote

Is it the magnetic field that is creating the current flow through the coil,or is it the current flow through the coil that maintains the magnetic field?.
A changing magnetic field is required to induce a voltage that then causes a current to flow.  The magnetic field is not changing, so you know you do not have electric current.  A current generates a static magnetic field.  But you know that your coils are not carrying current and by probing the surface of the magnetic material you can establish that it is not carrying a circulating current either.  All that you have is a soft magnetic structure that remains biased until you do something to break the alignment of the domains:  Heat above the Curie temperature, give it a whack with a hammer, apply opposing bias, or open the reluctance gap.