Re two-phase bridge rectifier/regulator.
The 2 thyristors in the rectifier bridge do not short the AC input or
"dump" anything.
On the contrary, they disconnect the DC output from the AC input when
the output voltage threatens to exceed the set voltage.
All output current passes through one branch of one diode and one
thyristor in series half the time and through the other identical branch
also half the time.
Heat development is proportional to the output current and the voltage
drop across a branch.
Voltage drops increase somewhat with current, so heat development
increases more than linearly with output current.
In the Ducati device the diode is reportedly a MR2510 pill (typically
0.75V at 10A, 0.8V at 20A), the thyristor can be a 2N6504 (typically
1.1V at 10A, 1.3V at 20A).
So at 10A the two branches of the bridge are each expected to generate
0.5 x (7.5 + 11) = 9.25W (total 18.5W) of heat.
And at 20A the two branches of the bridge are each expected to generate
0.5 x (16 + 26) = 21W (total 42W) of heat.
(
a failure mode for the Ducati device is reportedly the loss of
continuity of a diode pill attachment through thermal cycling; fitting
external parallel diodes has been proposed as a solution; replacing the
whole device seems more sensible
)
Cheers,
Jan de Jong
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