CHAPTER XV
SYNCHRONOUS RECTIFIER
SELF-COMPOUNDING ALTERNATORS—SELF-STARTING SYNCHRO-
NOUS MOTORS—ARC RECTIFIER—BRUSH AND THOMSON
HOUSTON ARC MACHINE—LEBLANC PANCHAHTJTEUB;—
PERMUTATOR—SYNCHRONOUS CONVERTER
138. Rectifiers for converting alternating into direct current
have been designed and built since many years. As mechanical
rectifiers, mainly single-phase, they have found a limited use for
small powers since a long time, and during the last years arc
rectifiers have found extended use for small and moderate powers,
for storage-battery charging and for series arc lighting by constant
direct current. For large powers, however, the rectifier does not
appear applicable, but the synchronous converter takes its place.
The two most important types of direct-current arc-light ma-
chines, however, have in reality been mechanical rectifiers, and
for compounding alternators, and for starting synchronous
motors, rectifying commutators have been used to a considerable
extent.
Let, in Fig. 72, e be the alternating voltage wave of the supply
source, and the connections of the receiver circuit with this sup-
ply source be periodically and synchronously reversed, at the
zero points of the voltage wave, by a reversing commutator
driven by a small synchronous motor, shown in Fig. 73. In the
receiver circuit the voltage wave then is unidirectional but pul-
sating, as shown by e0 in Fig. 74.
If receiver circuit and supply circuit both are non-inductive,
the current in the receiver circuit is a pulsating unidirectional
current, shown as iQ in dotted lines in Fig. 74, and derived from
the alternating current, i, Fig. 72, in the supply circuit.
If, however, the receiver circuit is inductive, as a machine field,
then the current, i0, in Fig. 75, pulsates less than the voltage, eQ,
which produces it, and the current thus does not go down to zero,
but is continuous, and its pulsation the less, the higher the in-
ductance. The current, i, in the alternating supply circuit, how-