SYNCHRONOUS RECTIFIER

241

the current in the rectified circuit is zero, and is high, is the short-
circuit current of the supply voltage, in the supply circuit.

Inductance in the rectified circuit retards the dying out of the
current, but also retards its rise, and so changes the rectified
current wave to the shapes shown—for increasing values of in-
ductance—as f0 in Figs. 87, 88 and 89.

FIG. 88.—Current waves of short-circuit rectifier on inductive load at the

stability limit.

Inductance in the supply circuit reduces the excess current
value during the short-circuit period, and finally entirely elimi-
nates the current rise, but also retards the decrease and reversal
of the supply current, and the latter thus assumes the shapes
shown—for successively increasing values of inductance—as i in
Figs. 87, 88 and 89.

FIG. 89.—Current waves of short-circuit rectifier on highly inductive load,
showing sparking but no flashing.
As seen, in Figs. 86 and 87, the alternating supply current has
during the short-circuit reversed and reached a value at the end
of the short-circuit, higher than the rectified current, and at the
moment when the brush leaves the short-circuit, a considerable
current has to be broken, that is, sparking occurs. In Figs. 86
and 87, this differential current which passes as arc at the com-
mutator, is shown by the dotted area. It is increasing with in-