TUBE 1W6643 - Caterpillar

FIG. 1 4N5110 REGULATORThe alternator output voltage varies in proportion to the rotating speed and the magnetic field intensity of the rotor.The voltage, always varying with the engine speed, can be prevented from increasing over a rated valve by the intermittent control of the field current (by charging the intensity of rotor magnetic field). The regulator does this operation.Features
The regulator is a mold type semi-conductor regulator, which has the following features as compared with the conventional contact point type regulator.1. Better voltage regulator accuracy. (No adjustment is required.)2. Longer service life.3. Excellent water-, chemical- and vibration-proof interior due to the adoption of plastic molding.4. Compact and easy to install. Handling Precautions
1. Be careful not to connect the battery cables reversely. If the battery polarity is reversed, the battery is shorted through the rectifier and a tremendous current flows causing damage of the alternator and regulator and burnout of the wiring harness.2. Do not confuse terminal connections. If the terminals of the alternator regulator are confused with some other terminals, the regulator will be damaged.3. Do not disconnect the battery terminals during operation.4. The regulator is a mold type and therefore can not be re-adjusted.Principle Of Voltage Regulation
The voltage produced by the alternator can be regulated by changing the field current.The regulator operates to cut off the field current when the alternator current has increased too much. Reversely, it permits the flow of the field current when the voltage has decreased, thus adjusting the intensity of the alternator rotor magnetic field to regulate the alternator output voltage.This operation is done by means of diodes, Zener diodes and transistors, which are described below.Diodes
The semiconductor comes in two types: N- and P-types. When these two types are joined together, the current flows only in the direction P N. This is called "rectification." FIG. 2 is a graph showing diode characteristics.
FIG. 2 DIODE CHARACTERISTICSZener diodes
This diode also has the rectification characteristics as the common diodes. But it has such a special characteristic that current suddenly starts to flow when the voltage impressed in the reverse direction has increased over a rated voltage (Zener voltage); the voltage across the Zener diode does not increase even if a greater voltage is applied.When the voltage applied decreases below the Zener voltage, the diode becomes non-conductive, cutting off the flow of current.
FIG. 3 ZENER DIODE CHARACTERISTICSTransistors
There are two types of transistors: N-P-N and P-N-P. This regulator uses the N-P-N junction type.In the N-P-N type, if small current (called base current IB) flows from the base to the emitter, large current (called collector current Ic: several ten times the IB) flows (ON) from the collector to the emitter as shown in FIG. 4.When no base current flows (i.e., when S.W in FIG. 4 is opened or when the base voltage is lower than the emitter voltage), the collector current IC does not flow (OFF).
FIG. 4 PRINCIPLE OF TRANSISTOR OPERATIONSubsequently described is the principle of voltage regulation by the regulator. The following basic circuit shows the operation