Re: generate 3 phase delta?


"BobG" <bobgardner@xxxxxxx> wrote in message
news:1134762031.681990.225680@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> BE:
> This is a four pole hysteresis synchronous mortor, B-2700 series. It
> runs at
> 1800 RPM on 60Hz single or three phase, 115VAC. It gives one ounce-inch
> of
> torque at 1800 RPM, 12 watts.
> To run single phase connect the AC line to the Blue and Green leads.
> Connect
> a 2uF, 200VAC capacitor between the White and Green leads. To reverse
> direction, connect the capacitor between the White and Blue leads.
> ===================================
> Hi Bob. I saw where one could run it from single phase with a cap....
> but I wanted to see if I could drive it with a microcontroller
> somehow...wondering how to generate 3 phase. I noticed it put out a sin
> wave between any pair of wires.... that's why I thought it had a perm
> magnet in it. Sounds like a lot of work. There's a dozen or so of em at
> Skycraft.

Yes you could generate three phase signals in a microprocessor. You'd have
to run the motor on higher voltage, however, 115 volts for 60Hz. You could
run at higher speed (frequencies) with higher voltages and lower speeds with
lower voltages. The volt-time product per cycle is held constant for
variable frequency drive. The frequency varies the speed and the constant
volt-time product keeps the torque controlled without allowing the motor to
overheat at low speeds. Usually such drives use pulse width modulation to
generate sinusoidal currents for the windings. Again a microprocessor could
easily develop the required three PWM switching signals for a three phase
system. The PWM signals would also incorporate the necessary constant
volt-time product characteristic. The drive elements for the motor could be
FETs or IGBT's or power transistors all driven from the processor. It sounds
like a big deal though just for a one ounce-inch motor. Such variable
frequency inverter drives are used on all kind of motors from fractional HP
on up.
Bob


.

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