With regard to how my alternators acheive 100 amps at a dead idle, that is a trade
secret I´m afraid, but suffice it to say they have more windings and more diodes (rectifiers).
Without question to best way to increase alternator life and survivablility is to reduce the heat generated within the unit. Many designs such as those based on the Delco 10DN do not have adequate heat radiation area for rectifier heat sinks. Failed rectifiers (either shorted or open) are a prime cause of stator overheating
(along with a bad voltage regulator
that overcharges - stator heat limit is dependent on wattage as well as amperage.
Even the large frame Ford alternators (many aftermarket manufacturers base their "premium" large frame alternators on this design) do not offer enough rectifier radiation area to maintain rectifiers within a safe level of heat. Very hot rectifiers are extremely prone to voltage transients (like when charging batteries
and having a 12VDC R/O unit cycle on and off).
Never EVER operate a large DC motor
while an alternator is charging especially if charging heavily. If a different engine
(like a generator) needs to be started - it needs its own battery
. Do not operate a 12VDC anchor windlass
when an alternator is charging. There are ways to get around this like attaching a large capacitor directly to the battery terminal on the motor
and correctly attaching an avalance diode such as a Motorola MR2535 (The pricey ZAP STOP) is such a rectifier, but by itself is not enough protection for onboard electronics
and the alternator/regulator. Capacitors of 10,000 uf and larger are useful.
Getting back to the alternator overheating
(insufficient heat sink area) problem; the use of an EXTERNAL rectifier (the term diode refers to devices rated 3 amps or less) chops a full fifty percent of the heat off the total developed inside the alternator. In reality the stator develops more BTU but when an external rectifier package is fitted the need for the positive heat sink inside the alternator is eliminated and it should be removed and that will vastly increase airflow within the alternator thus cooling
it better. The only downsides to an external rectifier package is that it requires a mounting space of around nine inches by ten inches by five inches high. The altenator must be modified to tap into its three stator phase terminals and wires run to thepackage. The positive battery wire is removed from the alternator and moved to the rectifier package and a large ground wire installed to the negative terminal on the rectifier package. The three stator wires running from the alternator to the rectifier package should be twisted so as to negate radiated 12VAC noise
Greeting from beautiful La Mira Michoacan (near where I live) I checked out the anchorage in Zihuatanejo on Sunday and saw one cruiser at anchor
and then went to the marina in Ixtapa and saw perhaps four masts, all of them belonging to craft of 40' and longer. Weather
85 degrees, humidity at the waterfront 65%, skies partly cloudy, wind
5 - 7 kts out of the east, and swells to five feet outside the harbor on the open ocean.
I'm glad I brought all my tools, test equipment
wires, heat shrink and terminals because such stuff is almost impossible to find down here. I remember walking onto the dock
at the marina in Barra de Navidad four years ago and it was a full month before cruisers set me free :-) When they learned that I had the 4-phase alternator I had to come up with six of them.
BTW one of the unsung discomforts of anchoring
off the grid and charging with an alternator is that the engine
develops a lot of heat and even more so if engine speed above the just-above-idle "sweet spot" is needed to produce enough charging amperage to make engine operate (fuel consumption) worthwhile. Misery = enduring a salon
with a temperature of a hundred and ten after charging batteries and trying to sleep in a broiling stateroom. Slower engine speed for charging therefore is crucial.
Hope This Helps!