Low power 3,6 and 12 phase systems

[CM800]

Hello folks,

Im interested in having a mess around with phased electronics (running at low voltages) as im just fairly curious about these things.

Does anyone know how to generate the delays in phase for the bridges in inverters

I know that
3 phase is 120 out of phase
6 phase is 60 out of phase
12 phase is 30 out of phase

Degrees out of phase = 360 / phases

i can therefore calculate the time dealy between each phase, but i am unsure as how to generate the time delays from my base square wave,

would someone reccomend a chip or diagram to help me with this

Huge thanks!
TCW

[johnwa]

Hi,

I have been looking at doing something along these lines myself, for testing some three phase circuits. You speak about square waves, are you looking at using some sort of switchmode output stage? You may be better off generating sinewave signals, and feeding them through linear power amplifiers. This will be somewhat inefficient, but probably acceptable for this application.

One approach is to start off with a single phase sinewave, and phase shift it using R-C networks to generate the three phases. I think Mike did a video on this for powering a three phase gyroscope motor. This is probably OK if you want a fixed frequency, but it will be a bit difficult to maintain the correct amplitude and phase if you vary the frequency.

Alternatively, a phase shift oscillator can be configured so that it is symmetrical with respect to the three phases, and all three waveforms are generated simultaneously. See for example http://www.4qdtec.com/wfg.html. This circuit gives a square wave output, but I imagine it could provide a sinewave signal if suitable amplitude stabilisation was used.

[jwm]

Hello folks,

Im interested in having a mess around with phased electronics (running at low voltages) as im just fairly curious about these things.

Does anyone know how to generate the delays in phase for the bridges in inverters

I know that
3 phase is 120 out of phase
6 phase is 60 out of phase
12 phase is 30 out of phase

Degrees out of phase = 360 / phases

i can therefore calculate the time dealy between each phase, but i am unsure as how to generate the time delays from my base square wave,

would someone reccomend a chip or diagram to help me with this

Huge thanks!
TCW

I use a 4017 for something like this and use or gates on the outputs to build multiple arbitrary synchronized waveforms.

    John

[qno]

Check out some theory about BLDC drivers.

3 phase motor control is done nowadays with a microprocessor or a dedicated chip.
Almost all microprocessor manufacturers have a 3 phase motor control app note.
Checkout Microchip, Atmel or any other of your favorite microcontroller manufacturer.

If you understand the principle it is quite easy to translate the 3 phase signal to 6 or even 12 phase.

Asuming you need 6 outputs to control the low and high switch of a 3 phase system you will need 12 for a 6 phase and 24 for a 12 phase system.

There is also loads of info on youtube. Search for "VFD" and some Indian professor will tell you all about it.