Lockridge Device - Peter Lindemann

[Matthew Jones]

@Matt
When you said you had a wire shorting out on your rotor I'm wondering if its acually the commutator case or prongs shorting out on the cover. Unless you ground down the 2 studs on the cover under the new commutator locations.

Mark

I just insulated them with a peice of rubber tape. I had just enough room. You could grind them a bit but I would leave the bolt hole intact.

I had continuity between the commutator and the steel in the rotor. I know where the winding failed.

I have been doing this stuff along time, and with that experience I have been able to not only predict and avoid some problems, but I can for sure diagnose and solve my problems. I am pretty independently minded technician.

Matt

[n84dafun]

It may be that your generating to some extent. Pulling a load off of a generator will slow you down.
With the Zig Zag pattern your on time very well might not clear the coil from the magnet. Follow Me.
The solution may be to use 2 commutator blocks for the power cycle. That will throw the coil out of the magnets range before you start recovering.

Then again you may just want to setup a recover for higher voltage and run that thing with a higher amount of voltage. But you had better recover into batteries, those little caps fill up too fast.

Nice work though, I happy to see the motor worked out.

Matt

Matt,

I thought about using two commutator blocks, but my brushes are too close together for that, so I just added extra contacts 180 degrees away. That did the trick and helped to get things spinning even at 3.7V. As I mentioned earlier the duty cycle for one segment is too short, and adding the extra contact segment worked for me. Maybe later I can reconfigure the brushes the way Peter recommended, then I can use two adjacent contacts, which would mean the distance between the power and recovery brushes would also be two contacts away.

The caps was just a test to see how high the voltage is in the recovery terminals. Since I didn't use diodes, it only stored 11V, which is misleading because the spikes on the scope were way over pos 50V and neg 50V, which averages to 0V.

Brian

[Matthew Jones]

Well its good to hear your working through it. Keep it up.

Cheers
Matt

[n84dafun]

I would think there shouldn't be any disruption in motor function when the recovery brushes are shorted. It should be a completely separate system from the motor. If it's operating like a generator at the point of discharge where when you short the leads it goes into full load opposing the rotation... maybe the diode should be reversed?

I didn't use a diode yet, so I'll try the diode tonight, maybe that will prevent the motor from bogging down so much.

Brian

[n84dafun]

Brian,

Thanks for showing your pictures. The rotor wound with the Zig-Zag winding looks GREAT. All of the problems you are seeing are related to your brush arrangement. When you switch over to the one I have recommended in Post #306, and connect your rotor wires to commutator segments 180* away from each other, the motor should behave differently.

After that, we can look at what your recovery brushes are connected to, and a voltage source that can deliver more current.

Peter

The zig-zag winding is so much easier to wind compared to what I was going to do, so thanks for pointing me to that direction.

I will play around with my current brush arrangement some more because I think there's still some potential with this arrangement (and plus I'm too lazy to reconfigure it all over again, I'd rather start with a fresh 16 pole motor. )

I was thinking of using my 10 amp battery charger for my voltage source connected to my 12V deep cycle battery. The thing is, it's not 24V like the recommended power for this motor.

Brian

[n84dafun]

Lockridge animation

Here's an interesting video:

YouTube - OTG- Lockridge animation 2 - DMR10.wmv

The commutator segments there are huge!!! compared to my tiny commutator on my motor. If I start with a new 16 pole motor I might have to connect several segments together like that.

Brian

[Peter Lindemann]

Drag from Shorted Recovery Brushes

Brian,

I've been thinking about why your system demonstrates drag when your recovery brushes are shorted. I think it is related to the fact that you don't have the diode in the circuit yet. In that case, it can act as a generator winding and produce reverse motoring. With the diode in place, it blocks reverse currents and only lets forward currents flow when the rotor coil discharges. I believe that with the diode in place, the drag should be reduced by quite a bit.

At least, that is what I think is going on. Good luck with your experiments.

Peter

[n84dafun]

Diode prevents bogging down of motor

I have confirmed it. The diodes on the positive recovery terminal prevents the recovery brushes from acting like a conventional generator when shorted together. It only let's out the spikes and doesn't slow down the motor. The weird thing is that it let's out both the positive and negative spikes according to my oscilloscope. Shouldn't the diodes only let out the positive spikes. Maybe my diode can't handle the high voltage spikes, only the low voltage generator pulses. Or maybe my diode is too slow to handle sudden discharge.

It doesn't charge a 4.7mfd, 63V cap very fast. Maybe 1 mV per second.

Brian

[Peter Lindemann]

Confirmation

I have confirmed it. The diodes on the positive recovery terminal prevents the recovery brushes from acting like a conventional generator when shorted together. It only let's out the spikes and doesn't slow down the motor. The weird thing is that it let's out both the positive and negative spikes according to my oscilloscope. Shouldn't the diodes only let out the positive spikes. Maybe my diode can't handle the high voltage spikes, only the low voltage generator pulses. Or maybe my diode is too slow to handle sudden discharge.

It doesn't charge a 4.7mfd, 63V cap very fast. Maybe 1 mV per second.

Brian

Brian,

Thanks for checking that out. The voltage spikes are very fast and most diodes can't catch the front lip of the event. But it is the currents that cause the drag, so they can deal with that OK. At this point, the reason the cap doesn't charge much is that we are still playing around at the bottom of the input intensity that I have imagined for these motors. The output pulse is dependent on the "change of magnetic flux" in the rotor winding. If most of that flux is produced by the stator magnet, it isn't going to change much to give us an output above the "generated voltage".

Remember, my stated plan is, once the machine is wired correctly, to run it on a voltage that is 3 times its originally designed voltage. When that is supplied from an "unlimited current source" like a battery, the rotor windings are going to be able to really TWIST the magnetic flux in the rotor caused by the stator magnets. THEN we will see the torque burst and (hopefully) the recovery pulse rise sharply.

Brian, since you are running your set-up on a limited current source, you won't see some of these effects.

I think it is a good idea to run the motors on low currents until we know they are wired correctly and all structures are in place, but that is only "Step One" in getting a motor to operate in this higher efficiency window.

Peter

[rosehillworks]

Peter. Thank you for your explanation! I think I understand what you are saying. I hope I have this right. If we pulse the rotor winding with a much more intense voltage and amps then what the stator flux can induce as back EMF that is when we will hopefully see the large recovery spikes, and good motor power.
Thank you for the reminder, and warning about what these spikes can do to an unprotected commutator.





William

[FRC]

Diodes

Brian,
Thanks for checking that out. The voltage spikes are very fast and most diodes can't catch the front lip of the event.
Peter

What type or kind of diode would catch the front lip? Or is this actually that important ? Or will it be important at higher voltages ?

FRC

[Armagdn03]

What type or kind of diode would catch the front lip? Or is this actually that important ? Or will it be important at higher voltages ?

FRC

Look for diodes with low parasitic capacitance, but can still handle the current rating. The current should not be for the instantaneous but rather the current averaged over time, as this is how semiconductors are rated.

[Matthew Jones]

Funny thing that zig zag

I got this thing wound up in the zig zag pattern. But what I didn't realize is it will only pulse 1 time per rotation. So you can fire it 1 time at TDC (according to the windings) but you cannot rotate it 180 then fire again.
So the thing is is you can put the diode internal. Put an out going diode on the end of your windings. This will both do the capture and block power from coming in at the 180 mark.
I am using a 600 volt 6 amp ultrafast diode. At 36 volt with 3.3 ohms of resistance on the wire I will push about 10 amp per pulse on the input. But the voltage should step up ( I think) to around to around 58 volt so the diode should be fine.

I'm getting ready to put it back together and run it.
I'll let ya know.

Matt

[Mark]

Well that would explain why have spent the last 2 hours trying to figure out why I can't get mine to run. Would get a little kick the it would kick back or lock up. I thought maybe I attached the wire on the commutator in the wrong spot have hace been rototing the brush cover all around the stator trying to get it to run.

Brian is using the zig zag pattern on his and his is running. But then I realized with the way he has his commutators set up he is only getting one pulse per revolution.

Please let me know if you get it going Matt.

[n84dafun]

4 pulses per revolution

Brian is using the zig zag pattern on his and his is running. But then I realized with the way he has his commutators set up he is only getting one pulse per revolution.

Please let me know if you get it going Matt.

Mark,

My setup actually has 4 pulses per revolution. Check out the circuit diagram below. That's how I was able to get it to run. Notice that for each quarter revolution, there's always a repulsive condition on the stator magnet from the rotor electromagnet. The poles flip when the current changes direction on the coil every quarter turn. I placed a jumper 180 degrees from the original commutator segment on the positive end and the negative end to make it work, as I mentioned in an earlier post.

Brian