Medium frequency systems can vary from 600 – 4000 Hz frequency. Most resistance welding systems are manufactured in the 1000 Hz range. Mid frequency welding can offer many advantages including weight reduction, power reduction and cycle refinement. So one might ask would more than 1000 Hz be better. At this time there are a few applications resistance welding applications using frequencies approaching 2000 Hz. The use of these higher frequency appears designed to take advantage of additional equipment weight reductions realized on some sizes.
Units at all of these frequencies would offer weight reductions, power savings and the cycle refinement expected with mid frequency resistance welding.
At this time for economic reasons the preponderance of business remains at 1000 Hz.
Units at higher mid frequencies above 2000 Hz may be in the market but are not know to the author at this time.
Reference: RWMA - Resistance Welding Manual 4th Edition