How do you size a resistance welding transformer?

Calculate the duty cycle at 50%.

KVA sizing slide step 1

With the duty cycle calculated, use step 2 to calculate the actual power required to operate at the 50% duty cycle. Then compare the values to determine if the 70KVA transformer is sufficient for the job.

 KVA Demand rev

To get KVA demand at 50% Duty cycle we go to step 2 and calculate below.

KVA sizing slide step 2

The calculation gives a requirement for a 60 KVA Demand at 50 % duty cycle which is smaller than the 70 KVA transformer available. The 70 KVA transformer is large enough for this application.

Reference:  RWMA Manual- Fourth Edition, 19-8

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