TM 9-4940-549-14&P
Frequency Meter. The frequency Meter (fig. 2-4) indicates the hertz
x.
of incoming power when an external electrical power source is used,
and indicates the hertz of output power when the dynamotor-welder
is driven by the shop set engine. Normal reading is 60 hertz when
the engine is driving the dynamotor-welder at 1, 800 rpm.
120-volt, Single-Phase Circuit Breakers. The circuit breakers (fig.
y.
2-4 ) protect these circuits against overloading which could be con-
nected to the 120volt, single-phase receptacles. These circuit
breakers are rated at 30 amperes each.
120-Volt, Single-Phase Receptacles. 120-volt, single-phase power is
z.
available at the three receptacles (fig. 24) , R1, R2, and R3, when
the dynamotor-welder is powered by the shop set engine or by an
external power source. Only the R3 receptacle will transmit 120-volt,
single-phase power, when using only 120volt emergency power.
Power Selector Switch. The power selector switch (fig. 2-4) sets
aa.
the control panel for the source of power that will be used to run
the dynamotor-welder and/or the shop set.
In GENERATOR position, the dynamotor-welder is driven by the
(1)
shop set engine. The generator portion of the dynamotor-wel-
der will produce AC current regulated by the AC voltage adjust-
ing rheostat. Power is available at all terminals and recepta-
cles. DC current up to 300 amperes and 32 volts is available
for welding.
(2)
In CITY position, an external source of 240-volts AC 3-phase
power is connected to the input receptacle. The generator por-
tion of the dynamotor-welder is now used as a 25 H. P. synchro-
AC power is available
nous motor to drive the welder portion.
at all terminals and receptacles, as well as DC power for welding.
(3)
In EMRGENCY position, an external source of 120-volt AC single-
phase power is connected to the shop set. The shop set lights
and R3 receptacle on the control panel can be used.
(4)
In OFF position, all AC circuits are de-energized. When the
engine is running at 1,800 rpm, the welding studs are ener
gized for normal welding operations.
Control Circuit Breaker.
The function of the control circuit breaker
ab.
ac.
ad.
