TM 9-4940-549-14&P
by the engine or an external source of 240 Vac electrical power.
Electrical power is also available when the external 240 Vac power
source is connected to the shop set and the dynamotor-welder is
stopped,
ae.
240-Volt, 3-Phase, Circuit Breakers. These 4 circuit breakers (fig.
overloading in excess or 30 and 40 amperes, respectively. They also
protect the grinding and milling attachment circuits from overloading
in excess of 15 amperes each.
DC Ammeter. The ammeter (fig. 24) indicates the amperage of DC
af.
welding current only when welding is actually being accomplished.
The normal reading will vary with the amperage range selected at
the DC ampere selector switch and the fine adjustment made at the
DC ampere adjusting rheostat.
Polarity Switch. The polarity switch (fig. 2-4) is used to direct the
ag.
flow of DC welding amperes from the welding rod to the material
(straight polarity) or to direct the flow of amperes from the material
to the welding rod (reverse polarity). The switch must be OFF when
welding is not being performed to prevent possible damage.
DC Ampere Selector Switch. The switch (fig. 2-4) is used to select
ah.
the welding ampere range required for all welding to be accomplished.
Amperes lower than 30 are available for special application and up to
300 amperes for general welding. Each welding ampere range shown
on the switch shows a minimum and a maximum for the range selected,
that should be further adjusted with the DC ampere adjusting rheo-
stat.
DC Ampere Adjusting Rheostat. This rheostat (fig. 2-4 ) regulates
al.
the DC welding amperage within the ampere range selected at the DC
ampere selector switch. This rheostat may be removed from the con-
trol panel ant? moved to the welding site for remote fine adjustment
of DC amperage by using a suitable electrical cable to connect be
tween. the rheostat and the receptacle that the rheostat was original-
ly plugged into. Turn the adjusting rheostat' clockwise to increase
welding amperage and counterclockwise to decrease amperage.
DC Voltmeter. The DC voltmeter indicates the DC voltage output of
aj.
the welder and will show a maximum of 32 volts.
ak.
(Overspeed Safety Switch. The overspeed safety switch (fig. 2-5)
will shut the engine down at approximately 2,000 rpm or 66 hertz.
General. The function of the shop set enginie is to provide power
a.
for the dynamotorwelder.
Starting the Engine. Refer to figure 2-6, and start the shop set
b.
engine.
