Electric Motor Secrets

[hh1341]

Very nice, Jetijs.

Carl

[Jetijs]

Carl


Today I almost finished the timing:




There are two pieces of acrylic in that deepening of the polycarbonate plate. They are made so that they can slide all around the perimeter. And as soon as the perfect timing is found, you just tighten those nuts on the aluminum plates to hold the acrylic pieces in place. The optoswitches will be glued on those acrylic pieces. Unfortunately today I realized that I have only three optoswitches and the electronic store does not have them in stock, so the will have to order them and this can take time.
Thanks,
Jetijs

[StevanC]

what's the current progress regarding this build :-)
What are the benchmarks?

[Jetijs]

Hi StevanC,
so far I am waiting for optoswitches to arrive, they should be here next week.
What do you mean with benchmarks?

[hh1341]

Jetijs,

Your bench always gets top marks for the work that is done on it!

This is beautiful craftsmanship.

I think this is the ONE!

Carl

[StevanC]

Hi StevanC,
so far I am waiting for optoswitches to arrive, they should be here next week.
What do you mean with benchmarks?

1stly, I want to congratulate You a excellent build :-)

I really like it :-)

further, i hope You won't stop just by building it?

You will make some sort of benchmarks and tests?

I look forward to it, and testify there are people who would like to encourage You in Your effort



I would like to get this far with my build(s), but obviously am to lazy to make even photos and reports :-)
Have You ever considered opto-switches salvaged from old 'male' (ball type) computer mouse ?
I just wonder?

[LowTechIsCool]

Inductance Vs. rotor position

@broli
Your approximation of the inductor/capacitor circuit is what I imagine, except that the inductor value is changing, since the rotor position is changing.

As the rotor spins to center, the inductance is changing, decreasing?, and that means the amount of energy on the coils is decreaseing. If you forcibly rotate the rotor away from center you will increase the energy on the coils and you have a generator, at least i think so.

From this i imagine that we would like to to get our pulses to be a short as possible.

@jetijs
I am very busy right now with school, so it will be at least a month before I complete my motor. In the mean time I was hoping jetijs could give me some readings from his motor.

I was hoping that you could get some data on the time constants of the coils at different positions. That is the amount of time for the potential, of a fully charged coil, to drop by a factor of (square root of two) when it is shorted. The time constants can be taken when the rotor and stator are aligned, then when they are completely unaligned. If you can get more values in between that would be better, but you would need some kind of brake, since when you turn on the coil the rotor wants to rotate.

From the time constant i can figure out the inductance with respect to position and should be able to model the circuit. This should give some insights into timing, at least for me.

Finally, can you give me a make/model of the bearings you use?

Thank you,
Chris Corkum

[Jetijs]

Another update. I got my optoswitches today and finished the motor. So now whats left is the driving circuit.



Chris,
So far I can not give you any data about the inductance, but remind me again when the motor is up and running. I use SKF 2200ETN9 double row self aligning bearings.

Have You ever considered opto-switches salvaged from old 'male' (ball type) computer mouse ?

Stevan, those switches are too small and have a too small gap. They can not be used in this case

Thanks,
Jetijs

[Aaron]

Wsu

Hi Chris,

When your motor is done, is that something you're going to demonstrate at WSU...down in Pullman right?

[LowTechIsCool]

Here in Pullman, WA

Aaron,

I am planning on using it for my senior research project, next year. I will be having a number of people working on it.

Right now, I am building a motor to understand the process. Then I plan to make a better one next year.

-Chris Corkum

[Jetijs]

I am working on the circuit now.
I decided to use IRFP360 MOSFET's, because they have better current ratings. They are rated 400V max, so I used 400V transil diodes to protect the MOSFET's. This way anything higher than 400V will go through the transil diode to the ground. I use UCC27321P MOSFET drivers, one for each pair of coils. The output of each MOSFET driver goes to two MOSFET gates in parallel. That thing on the upper left side of the circuit board is a 7812 positive voltage regulator that converts input voltage from up to 35V to 12V for the circuit logic and optoswitches. When everything is ready I will post the circuit diagram.



Thanks,
Jetijs.

[cody]

Looks like you are using a PWM circuit to chop up your pulse on time to a higher frequency, why did you decide to use four separate ones instead of just one? This is a great idea to do that, ive been playing with it myself.

[Jetijs]

There is no PWM circuit on that board, just a simple drive circuit with a MOSFET for each coil. Four coils per motor. Here is the circuit from V2 motor:



This circuit was intended for only one motor with opposite coils in series, so only one transistor per two coils. Now I am using the same circuit, the only difference is that there are two such circuits on a board and each MOSFET driver triggers two MOSFET's in the same time. The ON time chopper circuit will be installed later.

[StevanC]

(snip)

Stevan, those switches are too small and have a too small gap. They can not be used in this case

Thanks,
Jetijs

ok,
I didn't realize the scale of the unit until recently :-)

I like it more and more , keep it up!

the cost is paramount to me (hobby builder) an I just found that used power supply fans make a great base for this stuff, so the size of an salvaged opto switch from a mouse could play for me.

I hope You "YouTube" it ASAP?

[Mark]

Are you using the 360 or the 450 mosfets