I'm looking for a component that essentially limits the current passing through it, but unlike a resistor, its resistance is not constant.
When the current passing through this component is below the "amperage threshold", its resistance is zero ohms. When the current is greater than the "amperage threshold", the component's resistance will increase enough to prevent the current from exceeding the "amperage threshold".
Unlike a polyfuse, this component needs to be able to switch on and off several hundred times per second.
Does such a component exist, and if not, how could a circuit be set up to do it?
Edit: my "amperage threshold" is around 30 amps.