Electric Motor Secrets

[lighty]

The changes for 24V will be simple and I already sent you all the necessary parts for those corrections so you won't need to buy anything. I'll contact you via mail with schematic as soon as I get a fever down (I managed to get a flu).

Until then keep playing. BTW- read my post about using DSO to directly measure power consumption and regeneration.

[Jetijs]

Thanks
I will do that. And get well soon

[Jetijs]

Hello,
Here is what I did today. I connected the output to the capacitor in the input section. Then I connected two amp meters. One just before the power supply negative terminal and the other behind the capacitor. This way I could measure the real amp draw of the motor and the reduced amp draw from the power supply. I connected my function generator to the optotrigger LEDs, so I could chop the pulses just as I want. Then I watched both amp meters and adjusted the frequency till I found the biggest difference in those readings. Of course, if the frequency is high, not much current can pass through the coils, I got a high pitch noise from the coils that varies according to the LED frequency and the rotor stays in the firing position. I found that if the square waves on from my function generator are with 50% duty cycle, I can get just about 50% recovery. If i increase the duty cycle to about 60-65%, I get about 60-65% recovery. But If I increase the duty cycle more, the amp draw gets just big enough to move the rotor in a nonfire position. So far the best result I had is 75% recovery. I did not write down at what frequency that was, I will do that later. All I wanted to know so far was how much can I get back. I think that 75% is a fairly good result.

Another interesting observation. If I put the rotor so that one phase is in the firing position and then just pulse the coil with high frequencies so that the rotor can't move because of too small current, the transistor of that phase gets almost freezing cold. I found this very interesting. This is the first time I actually observed this radiant cold effect. I have heard this may happen, but now I witnessed this myself

I will play more with frequencies and duty cycles and keep you informed.
Thanks,
Jetijs.

[Aaron]

cold transistor

Very interesting Jetijs!

Do you have an IR thermometer to measure the temp of the transistor? You probably already know but the temp reading won't be accurate on any shiny metal but needs to be on masking tape or something like that stuck to the transistor. Would be interesting to see.

[Jetijs]

Aaron, I have ordered one, it should arrive any day now
When it does, I will take the temperature measurements and inform you
Edit:
http://www.emuprim.lv/bildez/images/...unti_1/73_.jpg
In the picture above you can see a scrrenshot of my scope settings and the waveform that shows how the optotrigger LEDs are flashed. These are the settings at which I got one of the best recovery results - 73%. I found the best duty cycle to be around 57% ON time and 43% OFF time. If we have a 50% duty cycle, then I can only get about 50% recovery. Anything past 65% and the recovery results go way down. Also the frequency is important. I found the best results at higher frequencies. I will get some input/output current waveforms at these settings tomorrow
Thanks,
Jetijs

[lighty]

Another interesting observation. If I put the rotor so that one phase is in the firing position and then just pulse the coil with high frequencies so that the rotor can't move because of too small current, the transistor of that phase gets almost freezing cold. I found this very interesting. This is the first time I actually observed this radiant cold effect.

Are you sure that MOSFETs are getting cold? Could it be possible that they're simply don't heat up as much as you observed before? If the latter is the case it would be consistent with the high frequency short duty cycle because of the very small current consumption resulting in extremely small power dissipation on MOSFETs.

Please do measurements to verify two important parameters of this configuration you're using. First of all measure current consumption of phase you're firing (put shunt resistor between Source of MOSFET and minus) and turn on RMS measurement on your DSO. RMS current measurement should give you pretty good estimation of the real current levels you're dealing with and you can easily calculate power dissipation on MOSFET for the given case. When dealing with frequencies over 1kHz and noisy, distorted signals most multimeters will give you false reading so you would really want to check that out with oscilloscope as I suggested in order to avoid false readings. A simple rule of thumb- when dealing with pulsed, distorted, noisy, high frequency signals trust only DSO measurement or if you have them, the mesurements of RF thermal voltmeter and ampermeter (or thermal wattmeter).

Also, when everything is turned off for some time in order to equalize with ambient temperature, dismount heat sink from MOSFET and press thermometer to it (body temperature thermometer will do fine for now). Now turn on circuit in the configuration that you suspect you're getting cooling effect and leave it running for at least 5 minutes. Thermometer should be pressed firmly to the MOSFET and if any cooling is occurring you should be able to see at least some temperature variation. During the measurement take care that you ambient temperature don't change and that thermometer is pressed to MOSFET with constant force and with some mechanical device in order not to transfer your body heat to the thermal connection.

When you get your IR thermometer you can make precise measurements but the measurements I suggested should give you at least vague idea if you got something tangible in your circuit or if it's but a combination of various factors playing tricks on you.

[Jetijs]

Lighty,
you are probably right about those various factors playing tricks on me
I played around some more and noticed that the MOSFET that is getting cold to the touch is that on who is currently not working, I mean, if I oscillate phase1 then the MOSFET of phase2 gets cold to the touch. It is possible that the metal part of the MOSFET just feels cold but in fact is at room temperature, like all metals feel cold to touch even at room temperature.
I will make these RMS measurements you said

This is what I learned today.
I connected the output of the motor to a battery. I put an amp meter on the positive side and the scope leads across the amp meter to see the output current waveform. Then I adjusted the duty cycle of the pulses and observed how the waveform changes. As I noticed before, there is a sweetspot in duty cycle where it is possible to get the best recovery and it is somewhere at 56-57% positive duty cycle.



Here we see the output current waveform with less than 50% ON time. You can see how small the waveform is in amplitude compared to next waveforms.



This is the same waveform, only this time the duty cycle is at about 56%. You can see how much bigger in amplitude the waveform is.



And this waveform is with 60% or more ON time. We can see that the off time becomes too short for the output current to discharge properly. With such duty cycles I can get only 50% or less recovery.
Thanks,
Jetijs

[lighty]

Could you please use RMS measurement turned on in order to get exact mean value?

[Jetijs]

In the voltage measurement options along with Peak to Peak voltages there are "RMS" and "Cycle RMS" By turning on either one I get some 10-20mV RMS readings What do you get from these values if you don't know the shunt resistance? I don't get it. I also have not been able to get a solid waveform when scope leads are connected across the shunt between the MOSFET source and minus. Only random noise. I suppose I don't understand something here

[lighty]

OK, when you're taking measurements of voltage drop on shunt resistor between Source and minus you have to observe several parameters:

1. Ground clip of your probe must be on minus and active end on Source. Between them is shunt resistor. Don't connect other DSO probe to any point.
2. Shunt shouldn't be inductive. For the current ranges you're measuring you need shunt of 0.1 Ohm (you will see 1V for every 10 amperes). Don't go for higher shunt values because it will probably heat up quickly. If the shunt resistance is too high it's resistance will impede current flow. If the shunt resistance is too low the voltage drop will be too low to precisely measure.
3. You need to know shunt resistance or you cannot calculate anything. You can use ampermeter and it's shunt resistance. Usually there is a value of shunt stated somewhere on the casing ampermeter or inside of it.

If you don't know shunt resistance of your ampermeter simply take adjustable DC voltage source and set it's voltage until you get ampermeter reading (in short circuit) of some known current value (let's say 1A or some other round number). Connect DSO probe in parallel with ampermeter shunt. Now you have current value (ampermeter reading) and voltage drop on shunt (DSO reading). Use Ohm's law to calculate resistance of shunt.

Now that you know shunt value you can measure RMS voltage directly with oscilloscope and use that value to calculate RMS current value. And again since we're dealing with pulsed DC and introducing noise you must observe that shunt resistor is non-inductive. Dedicated, calibrated shunt would be ideal if you can get one (it's not so expensive) but measurements with this configuration should also serve as well.

[Jetijs]

This is great.
So informative and easy to understand. Now I get it. If we know the shunt value and the average (RMS) voltage drop, we can calculate a precise power consumption using just the scope
Thanks

[lighty]

Indeed when measuring pulsed, distorted, ringing, harmonics rich signals RMS measurement will give you exact value you seek. In theory. In practice a lot depends on probes and their impedance as well as their bandwidth (also, do you compensate your probes from time to time- you need to do that), same goes for DSO but also higher sampling rate means more accurate calculation. Bigger buffer of DSO also means more accurate measurement over time (if you need one) etc. Differential configuration of two probes using math should help with noise to some extent - alway use that if possible.

The only other method that I know of that can deal with these kind of signals is by using RF thermal wattmeter. Relying on multimeters while dealing with these complex signals leads to inevitable false readings.

Also, you can easily measure output power on recovery coils using two probes and math function of your DSO (if your DSO has isolated inputs). So, connect the diode, capacitor, battery or whatever you're using to store recovered energy. Put shunt between diode and that "load". Connect second probe over that shunt (let's say it's CH2). Now, set appropriate values on your scope and use math function CH1xCH2. When you turn on your motor you will see power graph (on your DSO it's a red trace). Now, turn off CH1 and CH2 traces and turn on RMS measurement function. The RMS values of power graph will be presented in red letters. That's your recovered power in real time so when you change some parameter you will immediately see the effect on recovered power both in graphical as well as in numerical way. The same principle goes for measurement of input power if you don't want to use calculator- so connect one probe over the power supply (battery) and the other one over the shunt and repeat the procedure I described and you'll see power consumption graph. If your DSO have a hard time calculating stable RMS value simply set some higher value of timebase (to see more impulse signal on screen).

Now, if you had a 4 channels DSO with fully, galvanically isolated inputs you could do those two procedures at the same time and have both power graphs represented at the same time to see their relationship when changing some parameter.

However, if your two channel DSO has isolated inputs you could do the following- place one probe over the MOSFET Source shunt and put other probe over the recovery diode to "load" shunt. Use the same values for both channels and take both RMS measurements at the same time. You will have a relationship of two currents represented graphically as well as numerically so you can easily calculate input vs recovered power- RMS of course.

That's all for now, I'm still not feeling well and I really need to get some rest.

[elias]

Encouraging Results

I connected the output of the motor to a battery. I put an amp meter on the positive side and the scope leads across the amp meter to see the output current waveform. Then I adjusted the duty cycle of the pulses and observed how the waveform changes. As I noticed before, there is a sweetspot in duty cycle where it is possible to get the best recovery and it is somewhere at 56-57% positive duty cycle.

Jetijs

Dear Jetijs,

Thought to share an observation of mine to you. I had found out before that if I connect a parallel capacitor (The capacitance is not very much important, 330uF for example) to my output battery it would increase the recovery to the battery. The capacitor seems to be able to "catch" more of the recovery and redirect it to the battery. The internal Impedance of the battery is the main cause of this effect I suppose. I suggest you using a capacitor parallel to your battery and comparing the results. Good luck with your marvelous work!

Elias

[Jetijs]

Thank you elias
I will try that out and inform you how it went
Just an update. My new shaft is ready:

Thanks,
Jetijs

[Peter Lindemann]

One Year Anniversary!!!

Dear Everybody,

Today is the one year anniversary of this forum. I would like to thank each and every one of you who have participated for making this an intelligent, focussed, and civil exchange of ideas and designs concerning the possibility of Super-Efficient Electric Motors.

A special thanks to Aaron Murakami for starting this thread so that people studying my DVD Electric Motor Secrets would have a place to come for later developments and in-depth discussion.

Thanks again,

Peter