Alternator

Revmaster 2300 Engine Alternator

DISCLAIMER: This is not an official Revmaster site. It is just our (Dan & Tim’s) opinion. We do not work for the company, we are working independently. We are communicating our findings with them and hope to help find a solution for this great engine.

---

UPDATES

(update on 9/20/21) – There are several shortcomings of the alternator design but after 9 months of continual evaluation and study, no single failure cause appears to worthy of being labeled as the “primary cause.” The single change suggested for any improvement in the existing alternator OR for the alternator without any modifications would be “improved ventilation of the stator.”

(update on 9/20/2021) – Revmaster is designing and assembling an initial response to the failures of the alternators as a first step for overall PMA upgrade. I expect (but do not know for sure) that the bulk of the upgrade will begin with an alternator ventilation improvement. This, in my opinion, is the correct move as any improvement in the basic alternator will ALSO require improved cooling. I say this based on my own evaluation and for collaborations I’ve had with Revmaster on this topic.

---

Issue: Several alternators have degraded in flying airplanes. Some stator coils become blackened and the corresponding areas of the core material beneath them are charred.

The Revmaster alternator is a Permanent Magnet Alternator ( PMA ) design. If you would like to read about how they work please click on the button below.

The Revmaster PMA is a “series” regulator, in that when the battery reaches its voltage charge set point, the charge circuit is opened up and no current is allowed to flow to the battery OR through the alternator. The series regulator that Revmaster uses is sometimes confused with the alternative, a “shunt regulator.” This is important to understand because a shunt regulator would contribute to alternator coil heating with or without a charged battery. To repeat, “the Revmaster regulator circuit is NOT a shunt regulator.” The OEM R2300 regulator is a series PMA regulator.

R2300 alternator design: The R2300 permanent magnet alternator is built into the rear of the engine. The rotor is attached to the back end of the crankshaft. The stator is mounted in the center. The stator has 12 poles around the circumference. The ones at 12:00 and 6:00 are coils for the ignition system. The are five coils remaining the on the right side and five coils on the left side. The right and left sides each function as independent alternators. The five coils on each half of the (dual) alternator design are each “single phase” alternators. The 5 coils are spaced at the same angle spacing as the magnets. The coils are wound alternatively in CW and CCW directions and the rotating magnets are alternating North and South facing toward the coils. Said another way, the number of coils on the stator total 12, the same as the number of magnets, even though the coils are separated as 5 for one battery charge alternator, 1 ignition power, 5 for the second alternator charging, a the final single ignition power coil.

Some observations:

• Usually charring only on one side (right five or left five alternator coils)
• Can be just one coil, two, three, four, or all five coils
• Some alternators may have been still working while degrading
• While less common an ignition coil has charred (while a separate alternator coil also charred)

Possible Causes That Have Been Suggested and listed below with links:

• Charge Circuit
• Battery Type
• Regulator / Rectifier
• Alternator Short
  • Coil Inter-Winding Short
  • Coil to Plate Short
• Alternator Stator – Eddy Currents In Plates
• Alternator Stator Overheating (Coil Windings & Plates)

Click on a link above for a discussion of that theory and possible solutions. A summary table is below

Theory	Supporting	Cons	Solution
Battery Type
Rectifier
Alternator Short
Eddy Current
Overheating