Alternator: Description and Operation

The Boxster has a new compact alternating-current alternator.

Features:
- Power Output: 65 A at 1,800 rpm alternator speed
105 A at 6,000 rpm alternator speed
at ambient temperature 80 °C
- Weight: 6.5 kg
- Optimum ventilation to reduce component temperatures
- Zener diodes in rectifier: protect regulator and on-board electric system against overvoltage and voltage surges over approx. 33 Volts in negative and positive direction.
- Multifunction regulator BR1
- Closed-circuit current approx. 0.5 mA





Block diagram





Multifunction regulator BR1
Charge indicator
The connection for the charge indicator lamp on the regulator is indicated by "KI. L" (previously D +).

Pre-energization of the alternator
The pre-energization current no longer flows via the charge indicator lamp and parallel resistor. Instead, it is controlled by the regulator using a constant pulse duty factor. Therefore, the pre-energization current is not dependent on the output of the charge indicator lamp (1.2 W). When the ignition is switched on, pre energization begins if the charge indicator lamp is OK and the alternator is stationary.





Voltage regulation
Voltage metering and voltage regulation is performed at B + of the alternator. In low temperatures, the voltage is limited to 15 V.





Delayed increase in alternator current
(Load-response function)
To prevent the alternator from exerting a braking torque on the engine, the power output of the alternator is suppressed for a short period of time during the starting procedure and then gradually increased.

When the engine is at idle speed, a rapid change in load at the alternator is not corrected spontaneously as was previously the case. Instead, it is corrected slowly (ramp function). This prevents drops in engine speed.
A - without delayed increase in current
B - with delayed increase in current