Using 16f628 to make quasi-3-phase 400 Hz

[jtaylor]

I need to make three-phase power at 400Hz to run a pair of selsyn fuel-tank
units. It lookes like the simplest approach would be to program a pic and
run some audio power transistors from the outputs. I'd appreciate any
advice.

 

[Rene Tschaggelar]

I need to make three-phase power at 400Hz to run a pair of selsyn fuel-tank
units. It lookes like the simplest approach would be to program a pic and
run some audio power transistors from the outputs. I'd appreciate any
advice.

Yes, that depends on the required power level. For 10W that might be
doable. Above somewhere comes the level where a switcher is better,
meaning the increased complexity pays power wise.
You'll need a control loop whenthe load is not just a resistor, but
something dynamic, a nonlinear 4 quadrant load.

Rene

 

[Rich Grise]

I need to make three-phase power at 400Hz to run a pair of selsyn fuel-tank
units. It lookes like the simplest approach would be to program a pic and
run some audio power transistors from the outputs. I'd appreciate any
advice.

You don't need three-phase if what you have is actually selsyn motors. The
three "phases" are really just angle signals, from the one to the other.
The armatures just get single-phase. You still need to make it, but it's
easier to make a one-phase oscillator than three. And yes, you can
make a sine wave with a PIC, but you don't need it. Any old oscillator and
power amp will do, as long as you have enough power, but they certainly
shouldn't take a whole lot.

Good Luck!
Rich

 

[John Popelish]

I need to make three-phase power at 400Hz to run a pair of selsyn fuel-tank
units. It lookes like the simplest approach would be to program a pic and
run some audio power transistors from the outputs. I'd appreciate any
advice.

I think a phase shift oscillator is simpler, if you don't need a PWM
drive for the output. 3 opamps connected in a ring with a resistor
and capacitor as feedback. I think I have a schematic somewhere.

 

[CBarn24050]

Subject: Re: Using 16f628 to make quasi-3-phase 400 Hz

From: Rene Tschaggelar [email protected]
Date: 14/01/2005 20:16 GMT Standard Time
Message-id: <[email protected]>

You might want to look at the Hitachi 3048 chip. It has a 3 phase pwm
generator, you can get an evaluation/starter kit for a few hundred.

 

[Bob Eldred]

I need to make three-phase power at 400Hz to run a pair of selsyn fuel-tank
units. It lookes like the simplest approach would be to program a pic and
run some audio power transistors from the outputs. I'd appreciate any
advice.

If you are proficient in code writing, the PIC is a good solution whether
you need single phase or three phase. I wouldn't use a linear amplifier
though, I'd have the PIC drive FET switches directly in a PWM mode. Overall
that would use the least number of parts and be much more stable in both
frequency and amplitude than any analog oscillator-amplifier scheme.
Furthermore, it would not dissipate much power and would be applicable for
any power level from several watts to many kilowatts depending of the FETs
and their drive. It would be very good for low power, battery operation as
well if that is a requirement. On the other hand, if you don't know anything
about code writing in assembly or C, etc. Then your in for some headaches
and a simple oscillator-amplifier might be a better choice.
Bob