Mostly PM motor - Joe Flynn motor. My attempt to replicate

[gotoluc]

Also I tried to recover the inductive spike from the coils. I used some 5w light bulbs as a load. They light up, but the brightness is dependent on the input voltage. The sad thing is that when I attach the recovery part, the motor RPM's start to decrease and the current consumption goes up. I tried that with various timings and duty cycles. Always the same.
Jetijs

Hi Jetijs,

what I have recently found that works best for flyback recovery is to first see how high the recovery cap will charge to with no load. Then slowly add a resistive load starting in the 100K Ohm range and just keep adding resistors in parallel until your input current draw just starts to rise. Stop at this point as this will be the amount of free flyback energy you will be able to recover without affecting you input. Once you do the math you maybe surprised, as high voltage on a high resistance has a good amount of energy also. If you choke the flyback with too low of resistance you will disturb the balance.

All the best to you in your tests.

Luc

[Jetijs]

Thanks Luc
I will test your approach tomorrow.
Today I took the scope shots. And they are very interesting.
This one is the current waveform on one of the coils, measured on a 0,33Ohm resistor in series of the coil:



In this setup the duty cycle was about 60% and you can see that very well. Interesting are those negative triangles. That is a part of the second cycle. If the timing is off on one side, one of those negative triangles gets bigger and other gets smaller, and if the timing is off on the other side, the other triangle gets bigger and the first one gets smaller. The motor runs best when they both are equal. I guess that these triangles are showing up because the MOSFET has an internal diode and the induced power from the other phase is showing itself. But I am not sure.

Now, here is the same scope shot but with almost 100% duty cycle:


Now those negative triangles are almost gone. The motor consumes more current and rotates faster. The waveform does not change as the speed increases, just the frequency changes.

Also I made a voltage scope shot of the coil output when the motor is being run by a electric drill to see how it works as a generator. Here is the scope shot:



Those ripples are because the drill does not rotate at a steady force.
And this is the same scope shot with light bulb attached as a load:



Interesting thing is that I can get smaller light bulbs at max brightness and small RPM's, but bigger light bulbs say 21w bulb gets only moderately bright and there is no point in increasing the RPM's the bulb stays just as bright.

So those are my observations.
I would be grateful for someone to explain better what I am seeing and why it is working like this.
I will put a diode in series of the MOSFET to prevent the internal MOSFET diode to do its job and see what this does
Thanks,
Jetijs

[zhorv324]

Thank you Jetijs for the photographs you have shown with the osciloscop.
First let me explain what you call the negative triangles. As you assume, it involves the induced negative voltage in coil when the mosfet of the coil is turned off. What you see is the curent of the body diode of the mosfet. As you have noticed, the motor works best when both triangles are identical because then there's no diference in curent between your 2 coils. You can measure it with 2 ampermeters (every ampermeter on one coil). BTW I adjust position of the magnetic switches like that because I don't have osciloscop. You suggest putting a diode which will stop appearance of the triangles. Try putting the diode with high voltage and fast enough ,because of the BEMF which is pretty high. I can't achieve 100% of duty cycle so please tell me how the motor works in that condition during the load. Parallel path motor works even more strange as a generator. I tried connecting it with the driller only once but because of the bad construction (small berings) the test didn't last very long. I noticed that when the motor works as a generator you can put it in the short circuit and then it will give specific amout off curent regardlles on how high the speed of the driller is. I haven't succeeded measuring the change of the power of the drill during the diferent load on the generator because I don't have the watmeter but I really would like to do it. If you have watmeter I suggest to make the test-it could be really interesting. I hope I helped but trust me even I don't understand it myself. My motor works only with one coil because I use the full bridge configuration of the controler. There is no bigger changes in the work of the motor. The only advantage is that I have only one coil so there is more place for the diferent thickness and lenght of the wire. If you are interested to try it with the full bridge configuration I would pleasly send the sheme of the circuit.

[Jetijs]

Hi zhorv324,
Thanks for the explanation. I would like to see that full bridge circuit, that would help a lot

I also tried those diodes in series of the coils, this eliminates those negative triangles, but the thing is that if I use those diodes, the motor behaves the same when not loaded, but as soon as I load it, the current consumption goes way up. For example, without the diodes the motor consumes about 2.2A unloaded and almost nothing changes when the motor is loaded. But if the diodes are used, the motor consumes 2.2A when unloaded, but as soon as load is applied, the current consumption goes up to 3A.
Interesting. What do you think about that?

Here is the circuit I use now:


Those red diodes are the ones that makes the motor consume more power when loaded. If they are not used, the motor does not consume more power when loaded.



Thanks,
Jetijs

[Jetijs]

This is the scope shot across the drain and source of one of the MOSFETs:

[zhorv324]

Hi Jetijs. I posted the shemes of the circuit and 2 pictures which show the controler and regulator of the speed with SG3525 which is modified for needs of the motor. I can say that the diodes block the appearance of the induced voltage which "helps" the motor in its work as I assumed before. In the normal motor the curent depends on CEMF, the voltage induced in the coil which opposes the voltage applied on the motor. CEMF depends on the speed of the motor-decreas RPM and CEMF is smaller so the curent of the motor rise. That refers to all motors I am aware of. In parallel path motor that phenomenon acts completly diferent because the motor in one part of the work acts like the generator which uses that power inside itself (at least I think that happens). As you have noticed, when you try to draw that power from the motor, characteristics of the motor become the same as the characteristic in all others-when RPM falls curent of the motor rises. If you have any questions about the controler I wold gladly respond.

[zhorv324]

This is the scope shot across the drain and source of one of the MOSFETs:

IN oscilloscope shot is pretty clear that body diode works when mosfet is of

[Jbignes5]

just a hint

@Jetijs

Don't worry about the recovery of the spikes like it has been stated already that is as I suspect, built in. I think if you really look at the motor not changing in amp draw when being loaded is way over unity in that sense. You can generate outside of the motor much deeper then internally. As long as you can turn an extreem genny (harder to turn to generate more) you would find that PPm method is way more OU in what you do with that extreem loadability of the motor.
Even if you had to gear it, the shear power at even a snails pace could generate exponentially without having to pay for it or change how much your input is. The gearing would facilitate a wider loading capability on the PPm with speed being converted to torque. you might try paralleling the generators to see if a 1 input can drive multiple generators and see if that nets you a gain that way. you might not be able to have all gennies on at startup but might be able to add more as the process of ramp up of the speed of the PPm attains full rpm's with the help of a hybred transmission. The only thing you don't want to happen is PPm stall.
Why not make a neo gennie with the big neo's you have?

[Jetijs]

Hi Jbignes5,
Thank you! You are probably right. Anyway, I still have some other ideas about the recovery that I want to try out. If they wont work, I will still be happy

[Jetijs]

zhorv324
Thank you for your circuit diagrams I think I understand how they should work. This is what I need to test all the remaining recovery ideas I have and to do that I need one extra winding. If your circuit only need one winding, I will have a spare left to use for recovery and it will be an insulated winding
Thank you!
Jetijs

[Jbignes5]

I'm Sorry..

Hi Jbignes5,
Thank you! You are probably right. Anyway, I still have some other ideas about the recovery that I want to try out. If they wont work, I will still be happy

I am sorry for two things Jetijs...
1) I am profoundly sorry to barge into your most excellent innovation.
2) I am sorry for your workroom loss.

Now on to better things. Have you given the thought to using a rodin coil to energize your magnetic switches? it would take some redesigning of the cage but it could be done. The Rodin coil can energize the switches with less current since it has 60% more magnetic interaction inside of the coil then a standard coil. Just a thought. If you haven't read about it there is a forum post about the coils on here. It might be an interesting read for you?

[zhorv324]

Jetijs ,no problem I only wont to help you with your motor. And I have new proposal , you drive your motor with variable power supply if i m correct pleas put big capacitor ( at least 50000uF) in parallel with your power supply and se wot happen. I think the current of motor must be smaller. Next thing , use 12v (or 24v) battery to drive motor and measure current , but this time AC and tell me wot you see . Anyway I think that be interesting

[Jetijs]

Hi zhorv324
I ordered some somaller magnets for this motor, they will have 2x less square area so they should perform better in my current setup. I drive the motor with a variable 30V 20A power supply, it has a pretty big capacitor built in already. Anyway, at first I want to get the magnets right and to build your full bridge circuit. I have a question about your circuit, can you draw me a schematic of how the optos are connected to that circuit? Because it is not clear for me from the schematic you posted. Everything else seems nice

[zhorv324]

No problemo. AND i have small request, can you post oscilloscope shots when motor works with load at 75% duty cycle . Pleas capture moment when current start rise. I think that was pretty interesting thing to see

[Jetijs]

Luc, I tried your approach for the recovery with the cap and adjustable resistor as load. Does not work. No matter what value resistor I use, the current consumption goes up. The less resistance, the bigger the change.

zhorv324, thanks for the explanation about those optos. I will buy all the parts needed on Wednesday and try to build the full bridge circuit. As for your request, here are the scope shots of the current with unloaded and loaded motor.

This is the scope shot of the current across the resistor on the positive line directly after the power supply, so that the current of both phases must be there:

Unloaded:


Loaded:


And these are the shots across the resistor in series of one of the coils:

Unloaded:


Loaded:


What does this tell you?
Thank you!

Jetijs