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Open Circuit Voltage
The voltage between the two cable connections when the power source
is idling is called the open circuit or open arc voltage.
The voltage measured during the start of the ignition of the arc
is called the ignition voltage or arc starting voltage, this value
being the same as that of the open arc voltage. Arc starting is
easier with higher open arc voltages, but for safety reasons the
max. allowed open arc voltage figure is 120V. If the open arc
voltage is too low arc starting becomes difficult.
Working Voltage
The voltage between the cable clamps, during the welding operation
is called the working voltage. Standard working voltages are shown
below.
When welding, the voltage between the work piece and the tip of
the electrode end is called the arc voltage.
Welding Current
The current that corresponds to the working voltage is called
the welding current.
Nominal Operation
The nominal operation in standard manual arc welding is defined
by the actual welding time plus the idling time. The Swiss Standards
give the following example for the nominal operation;
If the period of a whole welding cycle is 2 minutes, 60% of this
is the total working time (72 seconds) and the remaining 40% (48
seconds) is the idling time. One cycle composed of the working
time plus the idling time is called the nominal operation.
Continuous Welding Current
The continuous welding current is the current that may continuously
be drawn from a welding power current.
Nominal Welding Current
The highest current supplied by the welding machine at a 60 loading
ratio is called the nominal welding current.
Adjustment Range
The adjustment range of a welding power source is the range limited
by its lowest and highest current it can produce.
Duty Cycle
The ratio of the actual welding time to that of the working plus
idling time multiplied by 100 gives the duty cycle. For example,
if a welding process lasts 3 minutes and the welder spends 2 minutes
to remove the slag and to place a new electrode in the electrode
holder before starting a new cycle, the duly cycle is:
% Duty cycle = (3 x 60 x 100) / {(3+2) x 60) = 60
The current indicated on the label of a welding power source is
the highest current to be supplied by this machine al a 60% duty
cycle. If a power source which can supply 300A at a 60% duty cycle
welds with 350 Ampere, what is the duty cycle? %
Duty cycle = (300x60)/350=44
The duly cycle of a welding power source can be calculated as
above and also according to the following chart. This chart is
very useful especially for comparing various power source.
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