INDUCTION-MOTOR REGULATION 143
chronous motors and converters, increase of their field excita-
tion frequently restores their steadiness "by producing leading
currents and thereby increasing the power-carrying capacity
of the supply system, while with surging caused by instability
of the synchronous motor the leading currents produced by
increase of field excitation increase the surging, and lowering the
field excitation tends toward steadiness.