The type of dimmer you need to handle a inductive load is called a Magnetic Low Voltage Dimmer, they are made to adjust the input voltage 0-120vac to a step down transformer/low voltage for lighting. I leave the shunts in my rewound MOT's because the transformers already draw too much current for their physical size. Shunts keep the current to reasonable level, they are going to saturate and get hot anyway so just don't push them to much as in a rsu. Spot welding is a different story, they
can stand the overload for milliseconds, but for rsu at 3-5 seconds , well they just get to hot.