Reducing electrical noise

My neighbor’s CNC machine induces a lot of electrical noise into my appliances whenever the machine does a brake maneuver (this is when a 3 phase motor is wired in such a way that it becomes a generator, hence it slows down quicker than letting it coast to a stop). I just hear loud buzz through my computer speaker, any induction cooker that are plugged in, etc.

How do I isolate my appliances from that? I think those CNC machine is leaking noise back into the grid and I imagine it’s also doing the same to the upstairs neighbor too.

There are two coupling mechanisms: conducted, and radiated. You’re probably getting a bit of both. Radiated noise usually couples in via the cables connected to your PC. If they don’t already have ferrites on them, buy some of the clip-on types and see if it makes any difference. You can use the same trick to cut down on conducted noise: buy a big toroidal core and wrap the mains lead through it two or three times. However these things only work for noise in the MHz range.

If you’re hearing an induction cooker making a noise, it’s more likely that the machine next door is imposing large, low-frequency disruption onto the mains power; in that case you could try an AVR, but that’s not a cheap solution.

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