MARRE DES PANNES d'alternateurs! j'ai besoin de ces alternateurs automobile comme back-ups afin d'avoir une source permanente de 12v quoiqu'il arrive. Les problèmes d'alternateurs proviennent neuf fois sur dix des régulateurs (pour les alternateurs à régulateurs incorporés) et des diodes de rectification. Pour moi, un alternateur est bon tant que ses bobinages cuivres ne sont pas toastés! J'ai donc viré les regu et les diodes et  conservé seulement les bobines stator et rotor. Les contacteurs graphite continuent de fournir le courant d'excitation aux bagues-pistes qui alimentent le bobinage du rotor et les bobinages stator produisent par induction le courant alternatif triphasé puisqu'il y a 3 enroulements dans le stator. simple comme bonjour!
Comme le triphase alternatif n'est pas untilisable et afin de remplacer les diodes originelles j'ai construit un rectifier universel à 6 diodes pour 75 ampères. Il est utilisable pour les alternateurs et pour le transformateur AC 230v - AC 17v.

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English

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FED UP WITH ALTERNATOR BREAKDOWNS! I need these automotive alternators as backups to have a permanent source of 12v no matter what. Nine times out of ten, alternator problems come from the regulators (for alternators with built-in regulators) and the rectifier diodes. For me, an alternator is good as long as its copper windings are not toasted! So I removed the regulators and the diodes and kept only the stator and rotor coils. The graphite contactors continue to supply the excitation current to the race rings that energize the rotor winding and the stator windings produce the three-phase alternating current by induction since there are 3 windings in the stator. Easy as pie!
Since three-phase AC is not usable and in order to replace the original diodes I built a universal rectifier with 6 diodes for 75 amps. It can be used for alternators and for the AC 230v - AC 17v transformer.

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 Alternator: Automotive alternator stripped of all organs
except the  copper windings. Rotor unchanged. 
Brushes directly connected to 12v circuit to feed
field current. Field consumption is 2.5 Amps in 12v.
Output is 47 Amps in 14.4v. Voltage loss is 0.7 v 
along the AC cables (1m) to the remote rectifier. 
Temperature after half hour run is 110°C and stable 
around the case near the coils. 4000 RPM at the pulley
insures good cooling. Remote 6 diodes rectifier is 
servicing alternators in 3 phase or transformer in single 
phase (2 AC conductors) one 10 000 ùF capacitor to 
smoothen DC ouput. Batteries 600 Amp/hour LiFePO4. 
Transformer: Modified stick welder 50 Hz 120 Amp. 
17 turns of 0.3 x 40 mm aluminium foil on secondary, 
17.5 v in open circuit. 240 v input from generator, 
40 Amps AC output in 14.5 v. 
Advantages: Simplified alternators unlikely to give 
troubles. Alternators and transformer are scavenged
items dirt cheap and easy to obtain. Backup for solar
installation only. Project suitable for alternative lifestyle,
independant from grid and servitudes and power bills.
 
A rheostat may be installed on the field feed line to adjust 
field current and output of the alternator. Higher voltage
suitable for Lithium batteries.