I have a possibly dumb question about currents in general and common mode chokes in particular.
Whenever I ask the advice of people who work with industrial servos, they always seem taken aback at how much current the little hobbyist BLDC motors are rated for. Their world seems to involve heavier motors with chunkier cables with lots more insulation, shielding, etc all round.
This seems completely at odds with what people who are building electric skateboards, e-bikes, drones, etc. seem to be playing with. Yet they don’t seem to suffer from problems related to heat, EMI, etc etc as much as the industrial servo guys would predict they do.
For example, I’m using a motor which states 80A as its max current. The wires coming out of it are 3.5mm dia, and that’s including the insulation.
The motor manufacturer chose to use the 3.5mm dia cables and I’m sure they know what they’re doing. I am just confused by the apparent contradiction.
This has come to a head recently when I started looking for a three phase common mode choke.
An 80A motor implies 80A through the coils, which means I need a choke rated for at least 80A. Unfortunately, they don’t seem to come that high, at least through the obvious channels. The highest I could find was only 46A and it cost £40.
Meanwhile, I made a homemade one with a <£5 ferrite core and a few twists of 3.5mm dia wire, and it seems to work fine.
I would like to source a proper component, rather than keep making homemade things if I can. But more generally - why don’t these two pictures match? If my homemade thing works, why aren’t they out there on the market? If it doesn’t work, then why does it seem to work?
What’s going on here?