WINDOW GP-CAB 1298842 - Caterpillar

potential difference necessary to gate (CR1). See Fig. 5. (R5) gives the potential difference necessary to gate (CR2). See Fig. 6.Normal Operation
Regulator Assembly
Regulator assembly (A1) contains resistors, rectifiers, capacitors and transistors in circuits connected to terminals 1 through 12 on the side of the regulator assembly. The regulator assembly is sealed in a non-conductive synthetic resin. This gives protection to the many components and complex circuits. The regulator assembly is serviced as a unit.The circuit illustrated on Fig. 7 is the AC voltage reference for regulator assembly (A1).Here the AC voltage is divided in direct proportion to the reactance of the sensing reactor and the combined resistance in the regulator assembly and the potentiometer. Because frequency varies the reactance of the sensing reactor, the voltage applied to the arm of the potentiometer is independent of engine speed of frequency change. This AC voltage reference also connects to isolation transformer (T1) priamry winding. The transformer isolates the regulating circuit and also prevents the voltage divider sensing circuit and the regulator circuit from becoming parallel circuits.The AC voltage from the secondary winding of the isolation transformer enters the regulator assembly through terminals (1 and 2). Terminals (1 and 2) lead to four diodes that make up a full wave rectifier which changes AC voltage to DC. This DC voltage is filtered by filter choke (L1) connected to terminals (3 and 5). The filtered DC voltage supplies a network of transistors, resistors, capacitors and diodes. The transistors in this network amplify and voltage variations in the input from the isolation transformer. This amplified voltage controls a timing circuit in the regulator assembly. Signals from the timing circuit, through terminals (7 and 8), supply the "gates" of control rectifiers (CR1 and CR2) with electric impulses which cause the control rectifiers to "turn on" the excitation circuit to revolving field (L3) [as required] to maintain constant generator output voltage.Blocking diode (CR11) prevents the gate signal from wire 7 from being shunted to the cathode of (CR1). Blocking diode (CR9) prevents the gate signal from wire 8 from being shunted to the cathode of (CR2).Control Rectifiers
CONTROL RECTIFIER SYMBOL
1. Anode. 2. Cathode. 3. Third terminal (gate).Control rectifiers (CR1 and CR2) are in effect, "on-off" valves that can either allow current to flow or can stop the flow of current through the excitation circuit. A control rectifier has the usual rectifier terminals, anode (1) and cathode (2), and a third terminal (3) that, for explanation purposes, will be referred to as the "gate". When gate (3) receives an electric impulse, it takes approximately three micro-seconds (.000003 second) for a control rectifier to "turn on" and allow current to flow. The control rectifier stays "on" until no current is flowing; then it turns "off". Because of no circuit from phase 3, current does not flow once during each complete cycle. Therefore, control rectifiers (CR1 and CR2) are "off" once each cycle and each gate must receive a signal to "turn on" the controlled rectifiers some time during