Confirming the Delayed Lenz Effect

[conradelektro]

.........
Conrad I see you are using square wave AC to drive the spinner ( H bridge ), that's then actually a "permanent magnet AC motor" not really a pulse motor if there is not an appreciable time break between input voltage alternations and no coil discharges or harnessing of the energy released when the magnetic field of the coils collapse. No big deal, just my opinion but to be a pulse motor the duty needs to be less than 100 % regardless if AC or DC is used. My duty is about 40 % or less. With lower resistance and slightly less inductance or higher voltage input it could be less.

Cheers
.........

@Farmhand:

The circuit I posted in my Reply #1272 on: April 30, 2013 can drive the ring magnet in "pulse mode" and in "attraction mode", depending on the polarity of the two drive coils (polarity can be changed by switching the wires of the coil). "Pulse mode" works better and uses less power for the same rpm. But torque seems to be higher in "attraction mode" (with more power used for the same rpm).

In "pulse mode" the coils should be farer away from the ring magnet than in the "attraction mode" for the same rpm, which seems to explain the higher torque in "attraction mode". "Attraction mode" would be the conventional commutating DC motor drive principle. If one does the commutating with a transistor H-Bridge it could be called an AC drive mode.

The ring magnet spinner only turns in one direction in both modes because the right polarity of the ring magnet has to be in front of the coil with the opposing polarity (in attraction mode) or the same polarity (in pulse mode) when the Hall sensor switches on the current trough the coils.

The circuit works with a ring magnet. I will only work well with a rotor having N S N S magnets facing the coils in case the magnets follow each other very closely.

I will try the conventional pulse motor circuits (only one transistor) with my Version 1 in order to have a comparison.

Greetings, Conrad

[conradelektro]

Comparison H-Bridge driver and single transistor driver for Version 1 of my ring magnet spinner:

I went back to a single transistor circuit with a Hall sensor for spinning the ring magnet in my Version 1.

The single transistor circuit is slightly more efficient than the H-bridge, but can only spin the ring magnet up to 5200 rpm. See the circuit, scope shots and photo (with the measurements).

It is not worth while to go from a single transistor circuit to an H-Bridge for a simple ring magnet spinner. May be that is useful information for experimenters who want to build a ring magnet spinner.

Comparison tests in the making: trigger coil instead of the Hall sensor in a single transistor circuit, DadHav's circuit with two MOSFETs.

Greetings, Conrad

[conradelektro]

Some progress:

Using two drive coils (opposing magnetic polarity at opposite sides of the ring magnet) in the one transistor circuit with Hall sensor makes it a little bit more efficient and allows to reach 7200 rpm with Version 1 of my ring magnet spinner. Power demand listed on the drawing.

I do not show scope shots because they are in principle the same as in my post above.

Note (look at the power demand lists in my post above for comparison), the power demand for 7200 rpm went down from 1.2 Watt (H-Bridge with two coils) to 0.72 Watt (one transistor circuit with two coils). And Version 1 does now 5000 rpm for 0.4 Watt or 3000 rpm for 0.2 Watt.

When trying a trigger coil, I have to place it next to one of the drive coils, may be in a 90° angle (like the axle) to the ring magnet.

Greetings, Conrad

[Farmhand]

I've made an improvement as well, I've got the input power down for the the rpm as well as shorter pulse width. Pulse width is just under 3 mS. Also I setup the boost converter with a max voltage of 20 volts and three settings for current. Still improving things and I have a new idea to reuse all reclaimed inductive energy with only one battery.

With two magnets the 360 degrees is split into two 180 degree cycles, if the drive coil has a duty of 25% that is 45 degrees so that should be the difference in phase, the charging inductor should be at about 45 degrees phase angle to the drive coil to get two phases from one pulse. I need to design a new signal processing circuit that retains 25% duty at all speeds. Then it will have more torque. At present at the lower speeds the duty is less and less.

Acceleration Test 1
http://www.youtube.com/watch?v=Yukaj0QQzN0

Considering it is really a single coil motor made to use the charging inductor as a second phase it is fairly efficient and responsive. With a second Twin coil arrangement it will have a fair bit of torque, I think this would work well for a pushbike motor-generator, with a larger rotor mounted on the bike's rear hub which has about 18 magnets as closely spaced as possible. If the bike wheel did say 5 revolutions per second and the rotor had 18 magnets that would be a frequency of 90 Hz. And with a 27 inch wheel that has a diameter of about 2.2 meters that is 11 meters a second or 39 kph. 

Would be helpful for reducing effort and going faster.

And if the circuit was switched off, then the diode after the battery is bypassed it would generate and charge the battery when rolling down hill or braking. A "swing in" generator coil could also be used so that it is out of the way when not in use.

It's a case of "Have TIG welder and plasma cutter. Will build crazy bike". I've got a history with powered push bikes. some years ago I installed a 2.5 hp two stroke victa lawn mower engine on a mountain bike, it had a direct "cylinder" friction drive to the rear wheel, the drive roller was mounted directly on the crankshaft. It did over 70 kph, and accelerated very well.  The sound of a 70 kph lawn mover really freaked out the neighborhood dogs though. hehehe.

Cheers

P.S. I would like to plot the acceleration and torque curves of this setup. A fixed timing point can be used with good effect so accelerating it is just a matter of input voltage control. It does have a "power band" or "torque band" so to speak.

Prototypes are not meant to be pretty. I don't understand people spending big time and big bucks on unproven prototype setups, it's not smart in my opinion, "pretty is, as pretty does" so Mr Gump would say. (referring to "Skycollection's pretty setups")


EDIT: Timing effect video clip. http://www.youtube.com/watch?v=KtgPwqJOZJk

..

[Farmhand]

Here I did a comparative test between the pulse motor with a fan blade on it
and a Small Purchased AC Fan rated to 15 Watts but only used 13 Watts when warmed up.

Pulse motor wins. 

http://www.youtube.com/watch?v=5orxI__rFsU

The pulse motor moves a lot more air for less power. I have another small fan
which is a bit bigger rated to 18 Watts, I'll see if I can outdo that one next.

Cheers