Electric Motor Secrets

[Jetijs]

Thank's Bryan
I have not studied anything of this is some engineer school, I had to learn everything by myself. In fact I am just a computer technician and a system administrator. We just have many tools and machines where I am working, so I have a chance to learn how to use them. Also I have built my own cnc machine, this gives me the freedom to machine almost any part I need. Here's a link:

Thanks,
Jetijs

[adam ant]

excellent quality work Jetijs. machining is definitely something that i wish i had studied. good work.

[Jetijs]

I made the comutator plate with magnets yesterday. The plate is made out od 3mm thick aluminum and the magnets are 1/4"x1/4"x1" neodymium type. They are spaced 90 degree apart of each other, the plate is bolted to a thread in the other end of the shaft, here's a picture:


My coil holder plates are also done and glued to the startor. I am almost done
BTW, we have our first snow today

[Peter Lindemann]

Awesome Work!!!

I finally got all the parts assembled to see how small the gap is. I must say, that it is a pain in the ass to adjust everyhing, it takes a lot of time. But when I was done, the air gap on each side was about 0.3mm or so. I could probably get it smaller, but I made too many mistakes in the building process, to the gap is as wide as it is. But its good for a prototype. Tonight I will work on the plastic coil holders. I will make them out of plexiglass and glue them on the startor with epoxy. Then all whats left is to wind the coil, but that should be easy enough Here's a picture:


The gap on the farthest side looks kinda big, but that is only the shaddow, because the rotor is in a little bit lower position than the startor

Jetijs,

Excellent work. Thanks for the picture. This machine will allow you to test a wide variety of the principles in my DVD. With the air-gap at 0.3mm per side (0.0118") your total air-gap will be 0.6mm (0.0236") or very similar to the little demo motor I have here, so you will not be able to see high torque production. No problem, just keep going and finish it. Its a great start for your research efforts and learning.



Peter

[Jetijs]

I finally got all the parts assembled to see how small the gap is. I must say, that it is a pain in the ass to adjust everyhing, it takes a lot of time. But when I was done, the air gap on each side was about 0.3mm or so. I could probably get it smaller, but I made too many mistakes in the building process, to the gap is as wide as it is. But its good for a prototype. Tonight I will work on the plastic coil holders. I will make them out of plexiglass and glue them on the startor with epoxy. Then all whats left is to wind the coil, but that should be easy enough Here's a picture:


The gap on the farthest side looks kinda big, but that is only the shaddow, because the rotor is in a little bit lower position than the startor

Edit: Here's the coil holders:

[Jetijs]

Peter,
recently I have been busy, because I have a job and can spare some time for the motor building only on the off work time. That is why I am progressing slowly, but I am getting there and nothing will stop me
In the mean time can you answer a question? So If I wind my startor coil from several parallel strands of wire, what is the difference between pulsing each of the strand with its own transistor and pulsing them all together with only one transistor, provided that the transistor can handle enough current? When I experimented with SSG circuits, I noticed, that I can get more RPM with two power coils if I pulse them with two transistors, each transistor for each coil. But when I used only one transistor and pulsed the both coils in parallel, I got only a little increase of RPM. Why is this so?
Thanks

[nali2001]

You can indeed pulse drive a normal big dc motor and recover like 80% and drive a second somewhat smaller motor from that, and so on(which is already o.u right there). But these motors normally do of course draw more under load. You can recover the back spike of nearly everything that is pulse driven, including transformers. Your battery won't really blow up since it is possible to transform the spike to lesser voltage.

Regards,
Steven

[sykavy]

I was speaking with a friend about the electric recovery to the second battery. He said that the attraction motor has the advantage of using less electricity because if you tried to recover the spike from a normal electric motor you would probably blow the batery up.
The attraction motor also stays at the same level of input while the normal electric motors vary up and down making recovery very complicated.
Does this sound right?

[Peter Lindemann]

Reminder....in case you hadn't seen this

Ahhh, now I understand correctly. Well in that case, yup, reed switch should me more than enough for the experimental purposes. I'm just not sure about the oscillation of the triggering signal and if any debouncing is needed, although I suppose if the trigger threshold od MOSFET is high enough that shouldn't represent any problem whatsoever.

Oh, and Peter, I do appreciate your efforts and patience!

Lighty,

Here is a link to the basic schematic of the machine Jetijs is building:

Rotary Attraction Motor Update

You can see that the little magnetic reed is just connecting and disconnecting the voltage divider section of the circuit. Plus, when the reed shuts off, the resistor R2 is still connected from the emitter to the base of the transistor, so the transistor shuts off quickly.

The little reed switches don't bounce as much as the larger relays because the reed itself is magnetized. They just clamp and release.

I hope this helps.

Peter

[lighty]

The little magnetic reeds cannot carry any current and I am only suggesting that they be used to TRIGGER an electronic switch, such as a transistor.

Ahhh, now I understand correctly. Well in that case, yup, reed switch should me more than enough for the experimental purposes. I'm just not sure about the oscillation of the triggering signal and if any debouncing is needed, although I suppose if the trigger threshold od MOSFET is high enough that shouldn't represent any problem whatsoever.

Oh, and Peter, I do appreciate your efforts and patience!

[Peter Lindemann]

Clarification, Please....

I beg to differ. The turn-off time of reed switch is several orders of magnitude longer than with any semiconductor. Since the inductive collapse voltage amplitude is a directly dependent on the shortness of that time it is very important to reduce that time as much as possible. Actually I compared the results when using a relay or reed switch and MOSFET. With the same current passing through the coil and the same core saturation level the inductive collapse voltage controlled with MOSFET was about 15-20% higher in comparison with electromechanical interrupters. Now, if one is into recycling the energy of the inductive collapse then one should consider using the semiconductor switches because for the same amount of current one could get back much more energy out of a coil. Of course the suddenness of the collapse is depending on a hysteresis loop of a core etc.

Lighty,

In the tests you refer to above, are you comparing the turn off time of a MOSFET carrying current and a large relay contactor carrying current?

The little magnetic reeds cannot carry any current and I am only suggesting that they be used to TRIGGER an electronic switch, such as a transistor. And again, this suggestion is only to get Jetijs motor running initially. In order to maximize speed, power and electrical recovery, more precise methods, as you suggest, will be required. I'm just trying to help him get the motor running with what he has. Improvements can be added later.

Peter

[lighty]

As for collecting energy from the turn off of the circuit, the reed is "slow" to actuate but very abrupt at the actual point of disconnect. This is the important feature, so it works just fine.

I beg to differ. The turn-off time of reed switch is several orders of magnitude longer than with any semiconductor. Since the inductive collapse voltage amplitude is a directly dependent on the shortness of that time it is very important to reduce that time as much as possible. Actually I compared the results when using a relay or reed switch and MOSFET. With the same current passing through the coil and the same core saturation level the inductive collapse voltage controlled with MOSFET was about 15-20% higher in comparison with electromechanical interrupters. Now, if one is into recycling the energy of the inductive collapse then one should consider using the semiconductor switches because for the same amount of current one could get back much more energy out of a coil. Of course the suddenness of the collapse is depending on a hysteresis loop of a core etc.

[lighty]

I live in Latvia, that is not too far away
Got any links form mu-metal manufacturers in Germany?

I could check out the address of our supplier. I will let you know via PM.

[Jetijs]

Ok, thanks Peter

[Peter Lindemann]

Try the #21 Wire First

Thank's Peter
I did not know, that a reedswitch can operate that fast. This is great
As for the coil wire. What about those cables with insulation? Can I use these? Because it is hard to get the magnet wire of that thickness here, but I can get a cable with insulation at every store. Here's a picture:


Of course the insulation would reduce the total count of the windings, but that is what is available here. I could order some magnet wire form ebay, but that would take weeks to deliver and would be more expensive. I don't see why i could not use such a cable instead of a magnet wire. What do you think?
Thank's
Jetijs.

Jetijs,

If you have the #21 wire, just start with that. Wire with normal insulation on it just takes up too much space, and does not cool very well, either. Start with 250 turns of #21 and see how it runs. If it seems speed limited, remove 50 turns and test again.

An alternate idea is to wind two or three coils (bifilar or trifilar) with about 100 turns each and then switch them in parallel, running each winding with its own transistor.

I do not recommend spending more money on Mu Metal or other wire at this point. Get the motor running with what you have.

As for collecting energy from the turn off of the circuit, the reed is "slow" to actuate but very abrupt at the actual point of disconnect. This is the important feature, so it works just fine.

Peter