Table of contents: Power ↓ Generator Maintenance and Safety ↓
Power
Depending on the year of production, engine and equipment, the Audi-100 was equipped with generators with a capacity of 70, 90, 100 and 120 A.
To calculate the generator power, you need to multiply the specified maximum current by the nominal voltage of 14 V. The result is, for example, 90 A x 14 V = 1260 W.
You have already noticed: the generator in a 12-volt on-board network actually produces 14 V. Because the battery can only receive charging current thanks to this small difference in voltage.
The transmission from the crankshaft pulley to the generator pulley is selected, by the way, in such a way that already at idle speed approximately ⅔ of the generator power is produced.
Generator Maintenance and Safety
The three-phase alternator, in addition to its relatively high power, has a major advantage: it produces current even at idle speed. In addition, its sliding graphite contacts (brushes) last more than 80,000 km. As its name suggests, it produces alternating current, which is not used in a car, since the battery can only be charged with direct current. Therefore, the alternator has 3 rectifier diodes built into it, converting alternating current into pulsating direct current. Since these diodes are sensitive to high voltage, you should remember the following:
When the generator is running, do not loosen or connect the wires between the battery and the generator. This may cause a voltage surge (voltage peaks), which will result in damage to the diode.
A three-phase alternator should not operate without a properly connected, working battery because the battery serves as a kind of buffer against overvoltage.
All cable connections between the three-phase alternator, battery and body metal or power unit (ground, body) must be tight. Even loose contact can lead to dangerous voltage spikes.
When charging the battery quickly (do not use when charging with charging devices with automatic shut-off) and when performing electrical welding work on the body, both wires must be disconnected from the battery so that the generator diodes are not damaged.
[The article is a reprint of material from AudiManual]