Frequency Meter. The frequency Meter (fig. 2-4) indicates the hertz
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.
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
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
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
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
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.
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.
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