‘Smart’ Circuit Breakers
The remotely operated switches in a distributed power system use electronic circuit breakers (ECBs). Current practice is to cluster several electronic circuit breakers in what I will call a Power Distribution Module, or PDM. The PDM is connected to the boat’s main two-wire bus, and then the individual circuits in one area of the boat (such as the lighting circuits in a cabin) are fed from the electronic circuit breakers in the PDM. A data cable connects the PDM to the boat’s control panels, and is used to trigger the electronic circuit breakers.
Whereas a traditional switch or circuit breaker has a given current (amperage) rating, an electronic circuit breaker is programmable. A boat builder can install a series of identical PDM units throughout the boat (so only one model has to be stocked by the boat builder, and kept as a spare by the boat owner), wire all the circuits, and then hook up a laptop when the job is finished and program the individual electronic circuit breakers to whatever trip characteristics are desired. This greatly simplifies the installation. If the equipment at the end of any circuit is subsequently modified, the electronic circuit breaker can be re-programmed. Electronic circuit breakers used on lighting circuits can also function as dimmers.
How a power distribution module works
Electrical circuit breakers control individual appliances, such as light or instruments, and are clustered together in a Power Distribution Module (PDM). Microprocessors in the PDM allow a great deal of control over each appliance.
1. The blue and brown terminals are the positive and negative feeds to six individual circuits; check the thumb for a size reference
2. The heavy black and red cables (see the image below) are the positive and negative connections to the boat’s main power junctions
3. The white buttons are the manual override controls for the electronic circuit breakers
4. The black squares in the middle are the electronic circuit breakers
5. This microprocessor runs the PDM and relays data
6. The entire unit is “potted” in resin to keep moisture out. With the cover removed, here's how the unit looks —