====== The Regulation Fuse ======

Your kart **must** have the appropriate regulation fuse installed in the correct place in your circuit in order to compete at any event. **The Technical Inspector will not permit you to race if you kart does not have the regulation fuse installed properly in your kart.**

The complete Operational-voltage to correct fuse chart is shown in the official rules (1.13.3) but since most karts on the field these days (and all recommended new builds) operate on the "48v" nominal platform, the correct regulation fuse is the [[https://www.digikey.com/en/products/detail/littelfuse-inc/142-5631-5302/2515908?|30A BF1 fuse available from Digikey]].

A fair bit of engineering sleuthing has gone into the behavior of these fuses so that races can optimize the performance of their Karts while minimizing the risk of blowing their fuse. A blown fuse costs precious racing time to change.

===== Changing the Fuse During a Race =====

The operator of the kart is not allowed to have a spare fuse on their person or in their kart. If you blow a fuse during the race, collect a replacement fuse from a race official (Timing and Scoring, The Grim, a Marshall) and install that fuse in your kart.

===== Time Curve Characteristics =====

The regulation fuse is a Slow-Blow type of fuse. This means, generally, that you can regularly exceed the printed current rating of the fuse, as long as the current you're instantaneously drawing through the fuse never crosses the line on the Time-Curve characteristic chart in the [[https://www.littelfuse.com/assetdocs/littelfuse-datasheet-142-bf1-58v|datasheet]]. The curve is also approximated in an accompanying table, so you can have a gut-sense of what kinds of over-current events the fuse may tolerate: 

  * at 100% of the rating (true) the fuse is designed to blow after 100 hours.
  * at 150% of the rating (45A on the 30A fuse) it will not blow before 90 seconds.
  * it is even guaranteed to accommodate 200% (double) the rating for 3 seconds before blowing. 

Calculus that is reasonably simple for a cheap microcontroller (like arduino or similar) to parse can be used to continually figure out the "area under the curve" against blowing the fuse, such that a dedicated engineer may even design a kart to monitor the current draw across the fuse and automatically 'throttle' the flow so as to prevent the operator from accidentally blowing their fuse. (Ask somebody whose made one of these monitoring chips at a race or on the discord to explain how it works to you -- it's above my pay grade)