variable-voltage, dc generator welding unit, and (2)
same time, the electrode tip is also melted, and
the rectifier-type welding machine.
metal from the tip is carried across the arc into the
molten pool. The decomposition of the electrode
covering shields the molten metal from oxidation.
Variable-Voltage, DC Generator
The temperature of the arc between the electrode
and the base metal is approximately 6500F.
This unit consists of a dc generator driven by an
ac electric motor or by a gasoline or diesel engine.
The voltage produced by the generator usually
ranges from 15 to 45 volts across the arc, and the
The Navy has a wide variety of shielded
current output varies from 40 to 400 amperes,
metal-arc welding equipment. In general, this
depending on the type of unit. In most units, the
equipment is classified as either ac or dc; either
voltage and ampere output of the generator is
stationary or portable; and either single-operator or
controlled automatically by the self-regulating or
multiple-operator equipment. In addition, it may be
drooping voltage characteristics in the generator.
classified according to the source of power and the
(An increase in current through the generator
number of amperes delivered at certain arcvoltages.
results in a decrease in voltage.) In addition, the
generator output is manually controlled by one or
The types of equipment available on any
two manual adjustments.
particular ship or IMA will depend upon the kind of
electrical power available and the size and mission
Welding machines of this type may have single
of the ship. Since most ships are equipped with ac
or dual controls.
In the usual single-control
power, we will discuss only the welding machines
generator, output is adjusted by shifting the position
that use an ac power supply or are diesel-driven.
of generator brushes or by moving a portion of the
Small combatant-type ships, such as destroyers, may
magnetic field structure of the generator. In the
be equipped with two motor-driven, single-operator,
usual dual-control generator, output is adjusted by
dc generator sets; whereas, cruisers and aircraft
varying the generator shunt field strength and
carriers will have a larger number of these types of
welders. The motor-driven dc generator set uses an
varying the strength and direction of the series field.
The machine shown in figure 10-l is a dual-control
ac power supply to run the motor, and the generator
type fastened on an ordnance handling truck. A
provides dc welding current. Repair ships and
ground plate is attached to the work to be welded,
tenders may also be equipped with diesel-driven,
and the electrode is clamped in the electrode
motor-generator sets as well as the electric
When an electric power supply is available,
All types of arc-welding machines require a
source of power that will allow you to strike and
welding generators are usually driven by an electric
maintain a stable arc suitable for welding. The
motor connected to the generator by a flexible
coupling. Others are set up with the generator and
principal sources of power for shipboard welding are
the motor on the same shaft. When an electric
power supply is not available, you must have a
A dc generator with variable voltage
characteristics may be used in a single-operator
welding system. The generator is so designed that
it delivers a voltage high enough to start the arc and
reduce the voltage as required to maintain the arc
during the welding.
A rectifier may be used to convert ac to dc
The power from these sources is used in various
types of welding equipment to provide the necessary
Figure 10-1.--Variable-voltage dc generator welding unit
current. The basic types of welding equipment used
f o r shielded metal-arc welding are (1) the