DrkAngel said:
Search the windings! Most all, have thermal fuses, look for the odd piece, or pieces, of small tape.
Or, look for the multiple ones in the controller, or, the one in the battery pack.
While it would be a good idea to have fuses in many pieces of electronics, lots of them don't actually use any, or at least not where you might expect them. Often this is because a failure that would blow it would happen so fast that the fuse could not blow before the failure was catastrophic anyway.
Another reason is it's cheaper not to put them in, by a little bit, and most of these things are made as cheaply as they can possibly get by with, safe or not.
Another really big problem with fuses is that if you use one rated for the max current you would want to preserve electronics at, it won't blow fast enough; if you use one rated to blow fast enough it will also probably blow just during surge currents of commutation, especially at motor startup under load.
None of the controllers that i've got, analog or digital, brushed or brushless, have fuses as such. They limit current by reducing the output pulse widths, or entirely cutting of output voltage when necessary, and if something so rapidly exceeds current capacity of the controller various components can blow up or vaporize, cutting off power, but they are not actually intended to be fuses, though the argument could be made that they might as well be.
In my NiMH battery packs, there are blade fuses, to prevent overcurrent draw on the pack. In the Vpower LiFePO4 pack, no; it has a BMS to limit current and for HVC and LVC, by turning off all the output MOSFETs, but it isn't really a fuse. Again, the semiconductors could blow or the shunts vaporize, but they aren't meant to be fuses, if everything is doing it's job.
None of the battery packs I have for tools, laptops, phones, or anything else have fuses, either. The charging inputs on quite a few devices I have do have fuses, but nothing on the path from battery to device usage point(s). Most of the laptops I've worked on over the years only have fuses on the exterior power input, but once it gets past that point, there are usually not any fuses; the BMS in the battery is usually expected to limit any output, and in a catastrophic situation, the FETs tend to blow, shorted, then often vaporize internally, usually cutting power at that point (and probably faster than a fuse would have anyway).
In desktop computers, the same tends to be true--very rarely have I seen even high-end PSUs or server systems with fuses of any kind (even resettable ones) on the internal power flow path--just on the external power inputs, and sometimes on input devices like USB ports or PS/2 keyboard and mouse ports (because if the wires inside a mouse cable become shorted after fraying from movement, you could have quite the interesting object d' art without any other limits on the resulting current flow :lol: ).
While most of the cieling fan, box fan and desk fan motors I've opened up have thermal fuses (or in some cases self-resetting thermal breakers), the small or large power tool motors haven't had them (in the windings; a few have had external current-activated breakers). Sometimes on big ones meant to run nearly continously under heavy loads there are thermal breakers, especially on stuff like condenser motors in refrigeration systems of various types.
I'd expected to find them in the induction motors in the washing machines and dryers I have used for parts, but only one had a thermal breaker in it, the rest don't have anything at all, other than (sometimes) a resettable current-type breaker on the power inputs to the control and user-interface section (but not to the motor power).
But none of the vehicle motors, brushed or brushless, have had them as part of the motors. Would've been nice if they did, since it might've preserved a couple of the ones I've got.
Even the larger of the two treadmill motors I've got doesn't, though the smaller one has a thermal breaker that could optionally be put in series with it's power connection (but isn't wired into it permanently, so it can be used without that; I don't know if it was used in it's original product).
So...there *can* be fuses or breakers in batteries, control systems, and motors, but there isn't always.
Most of the places I have seen them used tend to be where outside (wall-AC) high-voltage could, in a series of catastrophic failures, result in contact of that voltage with the user of the product, and where that isn't possible, they tend to be absent. I'm sure that's not a comprehensive rule of thumb, but so far is my experience.
