Quote:
Originally Posted by PAR_WIG1350
I understand why one doesn't want wires to burn up, but why aren't breakers used to protect components as well?
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Because they aren't designed to do that job.
Circuit breakers, like the ones in your home or on our FRC robots, are designed for wiring. They react somewhat slowly and actually allow over-current, that could fry electronic components, for a given period of time corresponding to how long your wiring will take to dangerously heat up. They react faster as the current surges higher, but still are only trying to avoid wire meltdown.
Home circuit breakers are designed to prevent fires inside your walls, not to protect your refrigerator. Breakers are designed knowing that multiple devices of unknown characteristics will use the wiring they protect over a period of many years. Many of the devices that they will eventually provide power to haven't even been thought of yet. Your home appliances all have their own individualized protection designed in. They all have to watch out for themselves, because they know what their design limitations are.
Electronics require custom protection with much faster response to protect delicate circuitry, and they don't like over-current at all. Window motors, on the other hand, only worry about heat buildup, so different devices require different protection solutions to be designed in.
The internal PTCs and special fuses in our electronics react very fast, at speeds required to save that particular circuit design and the more delicate electronic components.
Our window motors have thermal protection built-in to avoid meltdown in the motor, because it's a buildup of heat instead of high current that's the problem being solved, while a CIM solves the problem with more mass that absorbs much more heat and heavier gauge motor windings.
It all comes down to what each breaker, wire, electronic component is designed and rated to handle.
In this case, circuit breakers have amp ratings that are matched to wire gauges. Those amp ratings can be used to determine how many home appliances or robot devices can be supported on a single circuit, but they are not matched to protect each individual electrical component on that circuit.
With enough variety in fuse/breaker values to choose from we can approximate custom circuit protection. A good example this season was the Tetrix motor and the battery with it's 20a fuse. The 20a fuse protected the wiring from over-current drawn from the battery, not the smoking motors. We could compensate by substituting a much lower rated fuse, however, we'd have to change the fuse rating based on how many motors we had, essentially custom designing a fuse circuit to match our application, and it was a suboptimal solution because it would burn out over time anyway.