[Jon Stratis]

The inclusion of fuses on electrical components is a rather interesting topic. For the most part, fuses are used for safety. When examining the failure mode of a particular circuit, you need to consider the safety implications of such a failure. A few examples:

- Outdoor Christmas lights. Many of these have integrated fuses in them, as a failure in the circuit could start a fire on your lawn. This is doubly reinforced with a GFCI breaker on your outdoor outlets.
- In cars. There are numerous fuses in cars. These all are designed to protect the cabin from a fire caused by a short.

So, what about Spikes and speed controllers?

Well, with Spikes the failure mode can be pretty severe - the contacts inside a Spike are pretty large, and the plastic holding the whole thing together can melt. As a result, a Spike can short circuit, causing your breaker on the PDB to trip, or it could short the outputs to the inputs, causing the motor hooked up to it to be permanently on - a potentially much more dangerous situation, depending on what the motor is doing.

What about a speed controller? Well, speed controllers are much more complex. Generally speaking, failures in these end up with an open circuit - the motor simply won't work. This is a much safer failure mode.

Fuses can also be used to protect expensive equipment. For example, many surge protectors have fuses in them - the fuse will blow before your computer or TV is destroyed.