Explain your idea

Some times it would be great to have some way of either manually or automatically regulate the amount of Rf/t that a machine uses or that is allowed to pass through a wire, and this is something that could be helpfull with a lot of mods.

Since a lot of machines speed (both of Immersive engineering and other mods) is tied to the amount of energy they get, this could be used as a way of controling the speed of machine setups. Some machine setups use a lot of energy if operating at full speed and could easly overpower a power grid but don't have to run at 100% speed all the time, with a way to regulate the rf/t they get, one could control when to let machines run slow and steady and when to let them run at full speed.

This could also be usefull to limit the amount of energy a power line gets, for example to split a given amount of energy in different proportions between multiple lines or to stop unexpected events (like any sort of flying creatures from crashing into a HV line) from exeeding the maximum rf/t rate of a wire and burning the line.

In IE this could be implemented in the form of a variac or autotransformer, it could be a simple block with an input and an output for power and a dial on the top to swich between 15 states of what percentage of the input power it delivers to the output, it could also have a redstone port for controling the dial with an analog redstone signal.
idea of how could it be:

It could also come in the different variants of voltage, HV, MV and LV handling up to 2048, 8192 and 32768 rf/t respectively, the HV version could be some big 2x2x1 multiblock that can only be controled via redstone.

The only place where I've seen something similar is in Draconic Evolutions fluxgates, that allowed to control an amount of rf/t with redstone, and back in 1.12 I used them a lot.

Having such a thing not only fits in the style of the mod, but also could find countless little uses here and there, it's also a feature I have not found in any recent mod.

Some of the images I've found of variacs are crazy.

I got the idea when I saw this thing in one of styropyros vids.