Electric Motor Secrets

[Vincevl]

Rotary Attraction Motor

Attached is a picture of my RAM but I'm having a problem. My coil is wound with 245 turns of two pair Litz wire 18 AWG. The resistance of the coil is 1.9 Ohms. I assumed if I connect it to a 12VDC power source it would draw about 6 Amps but in fact it draws around 17 Amps.

Can anyone shed some light as to why?

Thanks,
Vince

RAM1.jpg

[gyula]

Hi Vince,

unfortunately it is only you who can this figure out, (you can do hands-on tests and visual inspectations... LOL)

The 17A current indicates 0.7 Ohm coil resistance instead of the 1.9 Ohm. Maybe try to move the wire connections up and down, and also sideways when your Ohm meter is hooked up, there must be somewhere a short between the turns.

I see the cross-spanner keeping the prongs distance for the air gap, is it magnetisable steel? sorry for this question...

Gyula

[iflewmyown]

Try touching the leads of your ohm meter together and read the ohms. Now record that number and then measure your coil. Subtract the the first number from the second and that will be a closer reading ( although still not very accurate ). On a harbor freight meter the first reading will usually be about .8 ohms.
Garry

[Vincevl]

Try touching the leads of your ohm meter together and read the ohms. Now record that number and then measure your coil. Subtract the the first number from the second and that will be a closer reading ( although still not very accurate ). On a harbor freight meter the first reading will usually be about .8 ohms.
Garry

You were right on! When I touched the DMM probes together I measured 1.2 Ohms! Here I was thinking it was a decent meter. No wonder my reading was wonky. I was able to measure the actual resistance by putting a constant 100mA load on the coil and measured the voltage drop across it to determine the resistance. It turned out to be 0.41 Ohms.

Many Thanks!
Vince

[Aaron]

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[Robert49]

Hi guys.

I haven't posted for a while, took a break!

I have reconfigured the circuit to better use the radiant pulses coming out of the coils.
I am now running on two sets of coils , collecting the spikes in a cap bank and running the third set on that energy. The spikes from this set are going to another cap bank and lighting a bulb. At first glance, higher speed, higher torque with less power in.

I will post the results soon.

Robert

[Robert49]

Hi guys.

Here's a drawing of my setup.
I'm driving the motor with two sets of coils, capturing the radiant spikes and driving the third set of coils with that energy.
I tested it with different voltages but the higher the input, the higher is the gain.
Example:
Point A-1 : 130 volts at 850 milliamps = 110.5watts
Point A-2 : ??? volts at 250 milliamps
Point A-3 : 199 volts at 652 milliamps = 129.75 watts
See post #1552 for diagram.

Robert

[Blargus]

It was worth the wait, congrats! So it works!

[Robert49]

It was worth the wait, congrats! So it works!

Hi.
Looks like it does.
I tested again and again and each time came up with positive results.
At some point I had 7 meters connected to make sure.
The thing is I don't know why it works, I did it out of inspiration rather than knowledge. I think the geometry of the motor and the timing is probably the key.

Anybody has an idea please let me know.

Robert

[gyula]

Hi Robert,

Your coil 3 may form a resonant LC tank circuit with cap bank via the lower MOSFET's drain-source (nanoFarad) capacitance and this may explain why the current meter A3 (652mA) shows higher value than A2 (250mA): the circulating resonant current inside a resonant LC circuit is (loaded Q) times higher than the current flowing into the LC circuit. Of course this does not explain everything, I do not mean it.
Have you checked the input current (A1=850mA) increases when you unconnect and then connect the lamp to the third set? Also, how the input current changes when you mechanically try to load the motor shaft?
Interesting circuit for sure, thanks for showing it.

Gyula

[Robert49]

Hi Robert,

Your coil 3 may form a resonant LC tank circuit with cap bank via the lower MOSFET's drain-source (nanoFarad) capacitance and this may explain why the current meter A3 (652mA) shows higher value than A2 (250mA): the circulating resonant current inside a resonant LC circuit is (loaded Q) times higher than the current flowing into the LC circuit. Of course this does not explain everything, I do not mean it.
Have you checked the input current (A1=850mA) increases when you unconnect and then connect the lamp to the third set? Also, how the input current changes when you mechanically try to load the motor shaft?
Interesting circuit for sure, thanks for showing it.

Gyula

Hi Gyula.
Thanks for answering my call.
There is about 15 watts on the light bulb when A1 is at 130v input.
I can't disconnect the light bulb. There has to be a load there otherwise the voltage rises and burns my 950volt transistor.

When I load the motor shaft, the amps on A1 rise but on A3 the voltage goes down and the amps rise.

I will make more tests and report.

Robert

[gyula]

Hi Robert,

Yes, I did not consider the lack of the lamp load may cause damage to the lower MOSFET, sorry.
Would like to ask about the timing of the 3 switches. What I would do as timing is that I would switch on coil 1 and coil 2 in a push-pull fashion, with lower than 50% duty cycle for both and regarding coil 3 I would switch it ON when neither of the coil 1 and 2 are ON (this latter requires a less than 50% duty for the two motor coils).

Sequence 1:

coil 1 is ON with 30% duty, coil 2 and coil 3 are OFF

Sequence 2:

coil 1 is OFF, coil 3 is ON with 30% duty, coil 2 is still OFF

Sequence 3:

coil 1 is OFF, coil 2 is ON with 30% duty, coil 3 is OFF

Sequence 4:

Coil 1 is OFF, coil 2 is OFF, coil 3 is ON with 30% duty

Now Sequence 1 can be started again and so on. How are your switching sequences done, I wonder.

Regarding the load on the shaft and the voltage goes down on A3 is okay but the amps rise is interesting if you mean the lamp current rise? How much current rise is involved approximately, does it mean that the 15W captured energy drops only a few watts? And if you meant the A3 current rise when the shaft is loaded, then it may indicate that coil 3 starts loading the input 130V voltage source? maybe because the load retards the rotor and timing slips a little for the lower MOSFET?
I know it may be difficult to attain the switching sequence I propose, it may need a microcontroller (Arduino or similar).

Thanks, Gyula

[Robert49]

Hi Gyula

I can see where you're getting at with the timing but if you look at the pictures on post 1536, I would have to build a new motor to do that.

The stator has three sets of four coils and each coil in a set is 90 degrees from the other arranged north-south-north-south.
The timing wheel has four slots and activates the opto sensors for each set in a 1-2-3 manner which gives 12 pulses per rotation. The motor was built to run this way.

Now when I load the motor as to reduce the speed to half, the amps on A-1 go up to 1.1a and on A-2 to 350ma. On A-3 the amps go up to 800ma and the voltage drops to 189 volts. No apparent change on the light bulb.

So input watts on A-1 =143 watts
A-3 = 151.2 watts
The motor feels strong.

Robert

[gyula]

Hi Robert,

Well, I did not study the motor pictures, I watched only your recent schematic where coil 1 and 2 is shown and read your description on the third coil so I answered accordingly, sorry.

Now you seem to have some extra output for sure. I wonder what is the capacitor value for your cap bank? Thinking on a cheap DC/DC converter for a possible looping but other than a PC power supply is not cheap and a computer supply is still not good without modifications as per its standard output voltages. (Nevertheless a PC supply is able to run from a 190V DC input instead of an AC mains.)
Or you may drive a motor as a generator (or a normal generator) by this motor's shaft and add up the two outputs.

Wish you good luck, very interesting setup!

Gyula

[Robert49]

Hi gyula.

The cap bank value is 60 micro-farads at 2250 volts.

Since the strength of a magnetic field is determined by amperes/turns, I will try a bigger capacity on the cap bank which should reduce the voltage on A-3 but raise the amps at the same time. If I'm right the motor should be stronger.

The cap on A-3 is 220uf 450v and is there just to even the spikes.

Thanks again

Robert49