You can calculate the actual duty cycle.
Example:
Given: Rated amperage = 200 amps
Rated duty cycle = 100%
Find new duty cycle if the machine is to be operated at 300 amps.
Ta = (200/300)^2 X 100% = (4/9)x100% = 44%
The value 200 is the rated amperage taken from the nameplate. Likewise the rated duty cycle is taken from the nameplate.
The value 300 is the actual welding current required. As one would expect, using the machine at a higher amperage rating is going to cause the machine to heat up quicker, so a longer cooling period is needed to prevent toasting the machine.
On the other hand, if the required amperage is less than the rated amperage, the machine can be used for a longer interval without overheating the machine.
Al