When a new motor is installed in a new building, it is specified by an engineer who wants to protect (or create) a good reputation, so it's going to be a really good motor. When that motor fails, years later, the replacement is selected at the discretion of good old Joe The Maintenance Man. JTMM's selection criteria are very different from the engineer's. First, Production wants that machine back up TODAY, so the replacement must be available locally, and from a vendor with whom JTMM already has an account. Second, the cost of the replacement motor will come out of JTMM's budget which is never enough to cover real costs, so it must be cheap. This means that if we are lucky, the replacement motor will be of the correct horsepower, rated for the correct voltage, and fit in the hole where the original motor sat. Thus, we design motor circuits for the worst possible motor JTMM might drag home in his little red wagon.
