Permanent magnet assisted motor coil designs

[captainpecan]

I learned a few things about this coil setup tonight. I have some test numbers to show.

These numbers are just comparing the original coil I made with the stack of washers, with the new coil I just made using the metal spacers instead. The spacers are much thinner in size. The original coil has 2200 turns on it and the second only has 1600 turns because I did not have enough wire to complete as many turns. I did make 2 taps so that I may run tests I will share next.

The test setup was simple. I used the cell phone app Gauss Meter to measure the magnetic field from a fixed distance from the coil. The app of course is picking up surrounding magnetic fields from other things inside the house, and was on average about .7 Tesla just sitting all by itself. I positioned the phone at a distance so that the reading was exactly 1 T (about 6 inches in this test). Then when I would turn on power to the coil, I can see the magnetic field reading and everything over 1 T is the change in field strength for that distance from the electromagnet. That is the number entered into the tables. It's not the best way to test I am sure, but it is what I have and I used the same consistency though out.

The data from these charts does appear to show that I may have been correct in my theory so far. My theory was that the stack of washers is overkill for the size of magnets I am using. It takes much more energy to saturate the core before I am able to see the effect the permanent magnet has inside the core. Although I am still not able use a power supply of enough voltage to successfully release the power of the permanent magnet from the core, I am able to see the effects of changing the core material, thickness, and turns of wire. It does appear that it is noticeably more efficient to cut down on the core material more than I had before.


***EDIT: All measurements in the charts are actually in GAUSS and not Tesla as stated.

[captainpecan]

This is comparing the results of repeating the same test 3 times. Each using a different tap of the coil which in turn used more turns and higher resistance. This does show that it is increasingly efficient the more turns you can get onto the coil. I am not seeing a point yet at which more turns do not do any more good for the magnetic field. I will be adding even more turns to this coil when more wire arrives. I plan to use more taps and keep increasing the coil until I see the point that it does no more good.


***EDIT: All measurements in the charts are actually in GAUSS and not Tesla as stated

[captainpecan]

The next test I did showed some very useful information. I am now comparing a hollow core to a permanent magnet core. I simply removed the magnet and all metal end caps to just have the coil with hollow spacers with 3mm thick walls. I then filled the core with metal so it was a solid steel core.
I immediately noticed a significant difference between the coil setups. Without the magnet in the core, the magnetic field was significantly less at the distance I was measuring. I also noticed that filling the core with metal made no noticeable difference. In order to see any real magnetic field from the coil. I had to move to within 1 inch of the coil.

This tells me, that with the permanent magnet inside the core, the core is more fully saturated now with the thinner wall spacers, that the field added by energy to the coil, it projected significantly out away from the core. Where as the core without the permanent magnet embedded, most of the energy goes into saturating the core and does not protrude that far away from the electromagnet.

The tests results shown here are testing both from exactly the same distance of about 6 inches from the core. If you move much closer to the empty core, you do see a much greater increase in magnetic field as the voltage and power increases. But it is significantly less than if the permanent magnet is embedded. I had to test at safe distances though because I did not want to subject my cell phone to any higher magnetic fields than I was sure it could handle. The next test needs to be pull force at 2 mm or so from the electromagnet.


***EDIT: All measurements in the charts are actually in GAUSS and not Tesla as stated

[Floor]

Real tests, real data, realy cool.
      thanks.

[partzman]

Cap,

Your tests are good for comparisons but you might want to check the magnitude of flux you are measuring.  Gauss Meter on my phone measures in gauss not in Tesla.  One Tesla = 10kG so a 1T measurement 6" away from a PM source is quite high from my experience.

regards,
Pm