Re: Looking to Cross ref a Diac & Triac set

There is a very good circuit for controlling the primary of any inductive
load. It consists of a switch in series with the ac input to the transformer
that pwm's the load. During the off time a second switch turns on in
parallel with the load. Each switch consists of fets or IGBT's either in
anti series or across the output ( + and - ) of a 4 diode bridge( fast
diodes ) . The fets/igbts are transformer driven ( both switches are driven
with the same transformer ) This will prevent the two switches from
conducting at the same time ( shoot through ). The output can be filtered so
the output looks like the output of a variac. The use of scr/triacs can not
be filtered very well and reek havoc with the switchers with cap input
filters.
Ray


"Ray King" <rayjking@xxxxxxxxxxxxx> wrote in message
news:%6jVh.10552$XU4.6424@xxxxxxxxxxxxxxxxxxxxxxxxx
Yes,

Fan motors are high slip and less inductive and more resistive. This
similar to a transformer with a full resistive load ( pure resistive). The
fan motor does not have as much mutual/leakage reactance that looks
inductive to the primary as the transformer with a pure resistive load.
Ray

"Homer J Simpson" <nobody@xxxxxxxxxxx> wrote in message
news:wviVh.14492$GV5.569@xxxxxxxxxxx

"Ray King" <rayjking@xxxxxxxxxxxxx> wrote in message
news:E1gVh.5575$Pq5.1492@xxxxxxxxxxxxxxxxxxxxxxxxx

Is this a diode on the ac input of of this circuit? Also is the load a
transformer? If either is true then the circuit will not work. You can
not control the primary of a transformer with a triac or two scr's at
least over the full range. you can go from zero to aproximately 75%

You can with the right design. Fan controllers do it.







.

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