Application Guide - High Current DC Welding with MAXQ™ Solid State Contactors
MAXQ™ SSR, QSDM- models, can switch currents over 1000Adc at up to 150V, making it suitable for many DC welding applications.
For welding, the most crucial aspect is to ensure the peak current or short circuit current that occurs at the end of the weld cycle does not exceed SSR's rated current.
There are two ways to determine the peak current. The first method is to calculate this value based on the maximum battery voltage and the total inline resistance in your circuit. The second method is to directly measure the full charge short circuit current with a current sensor. Once you have this value, you should add another 20% margin for reliability.
During operations, your welding cables could coil up, adding to the inductance with parts already in your circuit. Under this circumstance, it may generate a back EMF high enough to cause concerns. As a result, we recommend you place a freewheeling diode in the circuit in addition to select rated voltage rating 2x higher than the operating voltage.