Western Electric 407A-4, Instruction Manual

Page: 16 / 136

preliminary stages are derive d.
CB55P and contactor S51P control the app lication of
power to the cooling-unit motor s . Selection of the unit
:MBl . lW or l1Bl . 2W is controlled by the pos itions of D4. 1W or
D4. 2W .
CB56P protects the circu it which supplies power to the
pump motors MPl . lW and MP 1 . 2W and to the filling-pump mot or
MP2W. Selection of the active pump is accomplishe d by
Dl. lW and Dl . 2W.
CB57P controls the appl icati on of power to the prima­
ries ofT51P and T52P, which step the 460-volt 3-phas e power
to 230-volt 3-phase for energiz ing the modulating amplifier
filaments through CB 59P and S 53P and als o the oscillator
ampl ifier unit through CB 60P and S54P. In addit ion, 230-
volt s ingle-phas e power is supplied through CB58P to the
motor of T57P.
CB6 1P and S55P control the application of power to the
bias rectifier for the modulating amplifier, for 5-kw emer­
gency operati on only.
CB62P and S56P control the application of power to the
bias rectifiers for the modulating and power amplifiers for
normal operation.
CB6 3P and S57P control the filament circuits of the
high-voltage plate and the bias rectifiers .
CB 64P
in
connection with S58P, S59P and S62P and the
starting res i stors R51P, R52P and R53P control the filament
power for the 298A tubes .
CB73P, D55P, D56P and D57P form an is olating: and by­
pas s c ircuit to permit maintenance work on motor -operated
circuit breaker CB6 5P without interruption of stati on opera­
tion. CB73P is manual ly operated.
CB 74P provides protection for the supply circuit to
9