Frithiof Andreas Jensen
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 Posted:
Mon Dec 12, 2005 4:54 pm Post subject:
Re: 6 pulses rectifier |
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"Enzo Ternavasio" <info@enzoternavasio.it> wrote in message
news:439d4666$0$13263$4fafbaef@reader2.news.tin.it...
| Quote: | Is there someone who knows some micro/dsp to use in developing a 6 pulses
rectifier (or even 12 pulses).
I have a blackfin of Analog, but i do not know if there is something
better.
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I would choose ease-of-implementation over fast - mains commutated
rectifiers is usually an application that have response times that runs over
*many* 50/6 Hz cycles; The shortest response time will be the about 3.33
msec that it takes to swith one rectifier on at a new angle. IMO it would
require effort to find a CPU *not* fast enough or *work* to make it too slow
;-)
Look for chips that have driver logic built in. For example the Infineon
C166 - got 3 phase motor drive logic built in (and many other typical
"converter modes" by setting the right options). This is an old chip
Something similar and better might be around.
..
Beware of what is out there:
Some people derive the phase reference from some central clock locked to a
50 Hz reference off one phase - this is a common mistake that will show
excess output ripple and blow big fuses more often than it has to (Makes the
site tech happy though, I have about 700 grammes of pure Silver stashed from
such a job ;-).
You have to measure and control the firing angles on all the three phases -
because out in the real world, the 3 phase system might not be symmetric.
Essentially, what you will be building are three, single-phase, 2-scr
rectifier modules with the outputs paralleled and each phase controller
derives it's reference from the voltage between its own phase and the
midpoint/neutral. That works even when the system is skewed.
And then you might not need one "super-micro" to control it all - maybe it
is easier to use three for phase angle control and one for calculating the
phase angle, hosting the control algorithm and distribute it to the SCR
modules. The CAN bus might be plenty fast for that kind of thing.
So, cpus with: 16 Bit CPU, CAN, ADC and some drive logic is the business.
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