Principle of Operation

When the ignition switch is turned to the Start position, the circuit is closed.

Current then flows from the ignition switch via the warning lamp to terminal D+ on. the generator. It continues through the armature excitation winding and is then grounded via the voltage regulator.

When current flows through the armature a magnetic field is generated round it. When the engine is started and the armature starts to rotate, the magnetic field will also rotate and generate an alternating current in the stator windings. This alternating current is rectified by the rectifier diodes and the resulting direct current is supplied to the battery via terminal B+. The current obtained from the stator windings also flows through the excitation rectifiers (diodes) to the voltage regulator where it is used to control the output voltage. When the voltage rises to about 14 V or more, the voltage regulator reduces the current flowing through the excitation winding. This weakens the magnetic field as well as the alternating current generated in the stator windings. The voltage regulator accordingly limits the voltage to prevent it from exceeding about 14 V.

The warning lamp is also affected by the voltage obtained from the stator windings via terminal D+ on the voltage regulator, so that the difference in voltage on each side of the lamp is equalized and the lamp goes out. The lamp also indicates whether the generator is charging.

No current-limiting relay is required since the generator limits the current itself. At high generator rpm, when the frequency of the induced alternating current is also high and when the output current reaches a certain level, the resulting resistance (impedance) will be of such a magnitude as to render any further increase in current impossible.

You must:
never ground the excitation terminals of the generator or voltage regulator or the interconnecting cable;

never disconnect the voltage regulator or battery while the generator is running;

never remove the generator while the battery is connected;

never run the generator unless the voltage regulator is connected;

never test the generator and voltage regulator assembly in the car or on a test bench unless the battery is connected;

never reverse the polarity of the battery, as this could cause serious damage to the generator. Generators (alternators) should be repaired by a specialist workshop only. It is extremely important that dismantling and testing are carried out correctly, as even minor errors can cause major damage.


WARNING: To avoid damage to the rectifier diodes, disconnect the negative battery cable and all generator connections before carrying out any electric welding on the car.