466 ELECTRICAL APPARATUS
Permutator.—146. Machine to convert polyphase alternating
to direct current, consisting of a stationary polyphase trans-
former with many secondary phases connected to a stationary
commutator, with a set of revolving brushes driven by a syn-
chronous motor. Thus essentially a synchronous converter
with stationary armature and revolving field, but with two
armature windings, primary and secondary. The foremost
objection is the use of revolving brushes, which do not permit
individual observation and adjustment during operation, and
thus are liable to sparking.
Phase Balancer.—134. An apparatus producing a polyphase
system of opposite phase rotation for insertion in series to a
polyphase system, to restore the voltage balance disturbed by a
single-phase load. It may be:
A stationary induction-phase balancer, consisting of an induc-
tion regulator with reversed phase rotation of the series winding.
A synchronous-phase balancer, consisting of a synchronous
machine of reversed phase rotation, having two sets of field wind-
ings in quadrature. By varying, or reversing the excitation of the
latter, any phase relation of the balancer voltage with those of
the main polyphase system can be produced. The synchronous
phase balancer is mainly used, connected into the neutral of a
synchronous phase converter, to control the latter so as to make
the latter balance the load and voltage of a polyphase system
with considerable single-phase load, such as that of a single-
phase railway system.
Polyphase Commutator Motor.—Such motors may be shunt,
181, or series type, 187, for multispeed, adjustable-speed and
varying-speed service. In commutation, they tend to be inferior
to single-phase commutator motors, as their rotating field does
not leave any neutral direction, in which a commutating field
could be produced, such as is used in single-phase commutator
motors. Therefore, polyphase commutator motors have been
built with separate phases and neutral spaces between the phases,
for commutating fields: Scherbius motor. »
Reaction Machines.—XVI, 147. Synchronous machine, motor
or generator, in which the voltage is induced by pulsation of the
magnetic reluctance, that is, by make and break of the magnetic
circuit. It thus differs from the inductor machine, in that in
the latter the total field flux is constant, but is shifted with re-
gards to the armature coils, while in the reaction machine the