Does throat size affect AC welder performance?

Ohm’s Law defines current as:
                                                I= E/R
Where I is the current in Amperes, E is the potential in Volts and R is the resistance in Ohms.

In alternating current this formula becomes
                                                I= E/Z

Where Z is impedance measured in Ohms.

(Z) Impedance has two components. They are R (resistance) and X (reactance).

The reactance of the secondary AC circuit is subject to changes in throat welder size and proximity of any magnetic materials. Therefore welder throat size is a factor in welder performance.


Larger throat sizes (K or L) increases the reactance and therefore the impedance increases. By Ohm’ Law the current will decrease with larger throat sizes.


To optimize current flow minimize throat size and keep cables and conductors close together.

For additional information read article:

What is Impedance in Resistance Welding

What is Reactance in Resistance Welding


Reference: RWMA Resistance Welding Manual Revised 4th Ed Chapter 19

                   Roman Manufacturing Inc.


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