In fact, I only need to have:
- A logic systems behaviour: electric systems won't work when there's not (enough) electricity;
- A working charging-discharging total load amps gauge (same kind of thing have me headache with my D.21);
- Generator 1 and 2 amps gauge
- Main bus voltage gauge
- Fiveway switch: Battery, Gen 2, Both Gen, Gen 1, Off.
That's it. Item 2 is the most difficult, I guess. And there's the fact that I don't fully understand electricity yet... (don't tell anybody)
All consumers (instruments, lights, suit heating, motors, etc...) place cumulative currents (measured in
amperes) on a generator. If the resulting current is too great, the generator overheats and will quit by popping a fuse or spontaneous ignition. It doesn't matter if we're talking about generators (generating direct currents) or inverters (generating alternating currents) here. A landing light may place a load of 10 amperes on the main circuit while the bomb computer may place 5 amperes on it and the suit heating another 5. That's a total of 20 amperes on the main circuit. If your generator is limited to, say 70 amperes load and you're placing a load of 80 amps on it, it will quit and the circuit will be interrupted. In more modern planes, there will be a "bus tie" switch for this occation, which tells the remaining generator(s) to supply the devices on the circuit normally supplied by the failed generator. If the required load is greater than what the remaining generator(s) can supply, you need to prioritize which consumers are required for a safe emergency landing. I'm not sure about older aircraft, but the 727's generators have a lot of safety margin so that you'll only need to shut down some systems when you have one (of three) left.
If the generators on the T.5 were notoriously unreliable, implementing failures and forcing subsequent circuit shuffling could add some fun to flying it.
Volts describe the electric potential of an electric current and are affected by wiring resistance. You will therefor see voltage drops over a long distance that need to be compensated for (hence tons of 40000 volt overland power lines to supply 230 volts at a few thousand homes), but it can be assumed that generators and inverters in the simulator are always in perfect condition (and thus always deliver a constant voltage). Voltage is, however, important when dealing with batteries as it is the only indication for its load state. Each load placed on the battery, through wiring and consuming device, decreases its energy potential (voltage) because of the added travel for the "flow" through wiring or coil(s). The battery will therefor drain faster the more consumers you have connected until the electric potential of the battery is too low for the connected consumers to function. On the other hand, charging the battery from the generators will be slower when a lot of consumers are connected to the circuits. And for yet more added fun, the resistance of copper used in the wiring increases with temperature, so the time to discharge is also determined by the temperature of the wiring (or ambient temperature, if you will).
So to get back to the T.5:
The five-way switch controls your power source and thus the device your electrical load is placed on. With the engines running, turning the switch from "Parallel" (load split evenly between both) to either "Left" or "Right" will double the load on the selected generator. Charging the battery will also be slower because of the added loads.
The "main bus voltage" indicator will decrease when the battery is selected as a power source and read 24V (or 28V?) when at least one generator is selected.
The "total load" gauge might only be relevant for the battery. Simply add up the amperes of all consuming devices when the battery is the selected power source and give it a negative readout when the generators are charging it.
If you want to get nitpicky, consider the temperature dependency of the wiring and the subsequent voltage drop due to ambient temperature and make the "Veld" selector operational to compensate for it. The standard setting for 15°C or so could be 5 with higher temperatures requiring a higher setting and lower temperatures requiring a lower one. You can make instruments with a high voltage requirement working when the main bus voltage is not properly set despite running engines. When there's an overvoltage on the main circuit, you can make the fuses for some systems pop, requiring manual intervention. The fuses can also be used to adjust electrical load on the remainin generator in an engine-out situation.
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