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Some Definitions for Welding Power Sources

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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