The duty cycle of a power source: a major aspect

The definition of a duty cycle: Defined as a percentage calculated when the power source supplies electrical current in measured 10 minute intervals, and does not exceed an environmental temperature of 104°F (40°C).

What is the role of the duty cycle for orbital TIG power sources? When it comes to an orbital power source, the duty cycle defines the capacity of the equipment to provide power without overheating.

All power sources are equipped with temperature sensors, which activate, as soon as soon, as the machine is not cooling sufficiently.


Cooling of the power source: a key element of the duty cycle


Small power sources, even equipped with cooling devices, have a smaller cooling capacity when compared to bigger power sources.

Bigger power sources work under extreme demands, with higher duty cycles, they are equipped with water cooling systems which utilize bigger tanks. This is also true for the cooling fans, as their size is adapted for this kind of machine.


The duty cycle: considerations according to your application


As indicated previously, the duty cycle is a standard that indicates a certain percentage with an external environment of 104°F (40°C).

You will have to take into account the environment when you chose your power source, especially if you work outside, where the air cannot be easily cooled or heated, like in a workshop.

In addition, the volume of usage should be taken into account in order to insure the proper sizing of the power source.


Orbital power sources: welding thin tubes


Take the example of butt welding stainless steel tubes, with a wall thickness of 3 mm. Widely used in

  • the food and pharmaceutical industry,
  • in chemistry and biochemistry,
  • as well as for nuclear applications
  • and the fabrication of semiconductors, all of which belong to the “high purity” markets.

For this kind of application, a power source of 140 to 200 ampere will be often sufficient, especially if you use pulsed current.


Why use pulsed current for this type of application?


Pulsed current alternates the electric power from a high to a low level. Using pulsed current will keep your welding pool smaller and easier to control.

Here is simple example: If your high electric level is of 120 amperes, the low level will represent one third of the high level, at 40 amperes (As per our example). If the current is pulsed in a symmetrical way you will have an average value of 80 amperes on a tube with a wall thickness of 3 mm, which represents the limit for a simple fusion weld.

In this case, we recommend the choice of an orbital power source with a maximum capacity of 160 amperes, which will give you a wider margin.


It will be the power bridge that will define at which speed you pass from high to low current and vice-versa. This is not feasible in an instant way so small deviations might occur over time.

The duty factor is one of the important aspects to be considered when you choose a power source.

Are you looking for an orbital TIG power source? Our experts help you choose the right equipment!




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Écrit par
Frédéric Legrand

CEO and founder of AXXAIR