Active power

Performance is an important parameter in the world of resistance welding. In our case of resistance welding, we are dealing with electrical power:

P = U * I = I2 * R with U = R* I (Ohm’s law).

You can see that the power depends quadratically on the current. This is all the more important because a distinction must be made between active and reactive power in the case of alternating current. Active power is the power used in the welding point to heat and melt the material. The reactance of an AC circuit creates a phase shift between voltage and current. This phase shift is indicated with the power factor Phi. The active power is the product of voltage and active current. P = U * I * cos Phi.

From this it can be read directly that an AC resistance welding system must always provide enough power (current) to provide sufficient active power. Please take this into account when designing your machine. The active power is thus the electrical power that is ultimately effectively available for welding. It must be distinguished from reactive power, which cannot be used for this conversion.