Magnetic circuit simulation request

I have no experience using the programs available for finite element analysis and don't have the time to learn how to use one.. If someone experienced with their use could run a simulation, it would be of great benefit.

I have a microwave oven transformer of 1000W rating.

I would like to remove the "I" part of the core, leaving the "E" segment, along with the windings.

What I am interested in finding out is what happens when a permanent magnet pole is moved past the centre leg of the core.

What is the change when a metallic return path to the back of the magnet is provided? Think of a steel strip with the magnet in the centre. This strip would sweep across the three legs of the core.

What change with a large disc magnet in the centre of the strip and two smaller magnets with flipped polarities on the outer ends? I'm assuming the air gaps remain the same.

Any units of comparison would be great, as it's the *relative* output changes in the windings that I'm interested in. There has to be a way of simulating this on the computer. I don't want to build the project in real life until I can see some promise of success. This coil/core would become 1/9 of a wind turbine alternator and be rectified for use.

One of those neat multicoloured flux flow graphics would be interesting.

mike

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m II
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Yes, nice to get free work. Why dont you just do the experiment?

When it is open, the coupling is bad, so not much enery is transferred to the magnetron. Gradually when you slide the maget (which will transfer the flux) to fill the gap, you get 100% power to the magnetron.

The transformer does not care that you use permament mangnets, except if it would saturate, which it should not do, since it is a 50Hz transformer with high Bmax

If you only move past the center of the transformer leg, with a large airgap, nothinh happens. You need to bridge the gap

See above

None

Skip the microwave oven transformer, and buy a car alternator. Cheaper, simpler and works

Cheers

Klaus

Reply to
Klaus Kragelund

There's a program called 'vizimag' which may be useful, I think you get

30 days free trial. Slightly annoying user interface, but graphical and easy to use.

One thing to bear in mind is the permeability of the magnet - it may come as a surprise (it did to me) that, for example, Neodymium magnets have a very low relative permeability, not much more than air.

Cheers

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Syd
Reply to
Syd Rumpo

download free femm 4.2, join the group, ask there

Reply to
RobertMacy

That hurts...

The field on the alternator I have takes about four amps at thirteen volts. Losing 50 watts in lower winds is too inefficient.

mike

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m II

It's a PWM system... 4 Amps is at full load. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

You are probably right, if the alternator was in a car. This one has the field connections coming out and I vary the current through the field. A short to ground gives maximum current. The other end of the field winding is fed internally.

A permanent magnet rotor would be one solution, but there is another drawback. Car alternators have to spin a lot faster than the blades on a wind turbine. Once you get the gearing or pulleys sorted out, you've just added another loss of power.

Those axial flow permanent magnet alternators seem to be the best way to go, hence the search for prebuilt coils. A built in core would be a bonus.

mike

Reply to
m II

Alternators with PM rotors, typically only seen on motorcycles, "regulate" with a zener or shunt regulator.

You sound like you're out of your element when considering things electronic... CAUTION! I've seen automotive alternators produce 400V when unloaded and unregulated !!

It'll kill your ass faster than you can twitch >:-} ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

On Sun, 25 Aug 2013 13:18:31 -0700

I haven't seen a Zener used for direct regulation of output current on a motorcycle since the sixties and early seventies. The english bikes had them. Most modern bikes use three phase alternators with a regulated field winding. Harley might still use a single phase permanent magnet setup, but even they aren't dumb enough to use a shunt setup or Zener.

There is probably a valid reason to use a Zener inside the regulation circuit as a voltage reference for some transistor base or FET or something, but not as a direct dump to ground, as the English did.

mike

Reply to
m II

Then why aren't you PWM-ing your field current? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

Then that was superior to a Honda I had from the mid-70's! It just added loads across the battery dependent on whether you had the lights on or not!

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Mike Perkins 
Video Solutions Ltd 
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Reply to
Mike Perkins

I have no idea which bikes you are talking about, but every Honda and Kawasaki bike i have owned had a shunt regultor. At least 6 models form the 1980s to 2007 model years. I bought the service manuals for every one.

?-)

Reply to
josephkk

"m II" is clueless about alternators, and is going to ultimately injure himself screwing around... a Darwin-award candidate >:-} ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

I don't see any energy savings in pulsing the field instead of a steady DC current. If the batteries need sixty amps, there has to be a set current flow in the field. Any amount of pulsing would just serve to reduce the total amount of 'below the curve' field current.

I see no difference in my alternator compared to a transformer, the rotating primary being excepted, of course....and the resultant need for a DC vs AC flow.

mike

Reply to
m II

My understanding of 'shunt' may be at fault. The word to me means an alternate path for the alternator output current to flow. The English Zeners just dumped all the excess power to ground. They could do that with 150 Lucas style watts.

To my perhaps misguided way of thinking, changing the field current to regulate the output doesn't qualify as a shunt regulator.

Even on a permanent magnet Harley alternator, they have a series regulation on the output, with no flow to ground.

Think of railway terminology. A shunt is a parallel path to the main track.

mike

Reply to
m II

Might I suggest you learn how to calculate dissipation? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Do not forget the frog..

Reply to
Robert Baer

Then you will understand the benefits of PWM-ing. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

getting cross.....

mike

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Reply to
m II

Your understanding of shunt regulator is the same as mine. Every one blew off as much watts as necessary, as the rotor was permanant magnets (sometimes inside the crankcase oil bath region).

Gold Wings, most BMW MC and some other have proper fields coils and more normal regulators. Far more typical is PM rotors and shunt regulators, especially in smaller MC.

?-)

Reply to
josephkk

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