Ernest , Todd and Group,
Self contained and redundant electrical power system that will keep the engine running
without the battery after start-up...........I presume our planned PM alternators will keep our
engines running in the event our battery dies or is switched out of the electrical system ??
What say the more knowledgeable EE types of the group ??..........
http://www.eaa.org/experimenter/articles/2010-11_revmaster.asp
Accessory Case
This accessory housing package accommodates four items critical to engine and aircraft operations. It contains three major operating systems: the dual alternators, the self-energized ignition source, and the electric starter. And it also provides the physical mount to the airframe. The R-2300 model is nearly identical to the proven unit currently used on the R-2100 (more than 60 of those units are now in use) and is yet another product made exclusively by Revmaster. The three electrical subsystems are independent but function as an integrated unit within one compact aluminum case. Let’s look at each component separately for the sake of clarity.
The precision-machined alloy casting fully encloses the dual 18 ampere alternator package. Mounted to the interior face is a stationary 12-pole stator ring. An aluminum flywheel incorporates 12 neodymium iron-boron magnets that are attached to the interior of the flywheel. These magnets, the strongest magnets commercially available, rotate around the 8½-inch-diameter stator. Any movement of the flywheel sends its magnets orbiting in close proximity to the stators, with 12 feet each of copper wire windings exciting the electrons and creating electrical energy. There are two groups of five alternator coils, each set functioning as an independent 18 amp alternator. The current generated from these coils is sent to solid state regulators and then to the aircraft’s battery and operational power bus. In the unlikely case of a failure in one system, the other would remain unaffected.
Ignition
The two coils which make up the ignition power source are located 180 degrees apart at the 12 and 6 o’clock positions (see photo above), separating the previously mentioned five-left and five-right alternator stator coil groups. The ignition coils are also creating power whenever there’s rotation of the flywheel, but their energy is dedicated exclusively to the CDI (capacitor discharge ignition) package.
The back side of the accessory case, showing the ignition trigger sensors
A triggering sensor mounted to the center area of the housing’s interior receives a signal from a device attached to the end of the crankshaft, acting as the “distributor” and telling the CDI when to transmit the power to the eight mini coils which are positioned near the upper and lower sparkplugs at each combustion chamber. Once the engine has been started, the battery isn’t necessary to operate the ignition.
With the accessory case installed, timing the ignition is next on the list.
The ignition advance is set at a maximum of 25 degrees before top center. This would normally be identified as a fixed timing position, but in reality the “effective advance” behaves as if the low rpm timing is at 15 degrees BTC (before top dead center- sometimes BTDC). This desirable situation is created by magnetic precession in the self-energized design. Lower voltage exists in the system when the engine is turning slowly, reducing the current flow at the timing triggers.
The “brains” behind the brawn. Once the timing is set, the electronics are wired up and bolted in place.
The engine likes 15 degrees BTC for easy starting and comfortable idle. But as rpm rises so does the voltage and the ability to “snap” the timing, and the advance moves quickly to its maximum setting. Experience has proven that 25 degrees BTC, while possibly leaving a few horsepower untapped, is a smart place to limit the spark advance because it greatly reduces the possibility of destructive detonation.