COMPRESSOR GP-CLUTCH & REFRIG 7T8600 - Caterpillar

Voltage Regulator Circuits
The voltage regulator senses the generator voltage, compares a rectified sample of that voltage with a reference voltage and supplies the field current required to maintain the predetermined ratio between the generator voltage and the reference voltage. The KCR-760 voltage regulator is designed for three phase sensing and includes two sensing transformers (T1 and T3). The sensing circuitry also includes a transformer (T2) and potentiometer (R4). Transformer T2, potentiometer R4, and an external current transformer provide means of attaining reactive kVA load sharing during parallel generator operation. The parallel operation components do not affect voltage regulator operation when the generator is operated singly.Underfrequency limit (UFL) or V/Hz option circuitry interacts with the regulator sensing and error detector in a manner that decreases voltage during underspeed operation. A solid state flashing circuit operates each time the generator is started. The flashing circuit de-energizes when generator voltage has built up to about 70 percent of rated voltage output. Most of the circuits are contained on a printed circuit board. Parts that are individually mounted on the regulator case are the sensing transformers, parallel operation transformer T2, parallel voltage droop potentiometer R4, the power stage, and a fuse. External voltage adjust rheostat VAR is provided for installation on a control panel.Sensing Circuit During Single Generator Operation
The voltage sensing transformers provide a voltage proportional to the generator voltage output. This voltage is fed through the secondary of T2 to a full wave rectifier comprised of silicon diodes D3, D4, D17, D18, D23, and D24. The rectified voltage is filtered by resistor R3, choke L1 and capacitor C1. The dc signal from the filter is applied to the error detector and the underfrequency limit.Shorting the secondary parallel operation transformer T2, either by using the jumper bar across CT1 and CT2, or turning R4 to its full counterclockwise position or setting the UNIT/PARALLEL switch to UNIT position, eliminates the effect of T2 during single generator operation.Sensing Circuit During Parallel Generator Operation In Reactive Voltage Droop Compensation Mode
Generators interconnected for reactive voltage droop compensation will proportionally share inductive reactive loads during parallel operation by a decrease in generator system voltage. This method of kVAR load sharing is described in the paragraphs that follow.The sensing transformer provides a voltage proportional to the sensing voltage. A current transformer (CT) installed in line 2 of generator develops a signal that is proportional in amplitude and phase to the line current. This signal develops a voltage across the slide-wire parallel voltage droop adjust potentiometer R4. The tap on R4 supplies part of this voltage to the primary of transformer T2.The voltage developed in the secondary of the sensing transformer and the voltage developed in the secondary of T2 add vectorially. This action provides a voltage to the sensing diodes that is the vector sum of the stepped down sensing voltage and the parallel current transformer signal through T2. The sensing rectifier dc output is filtered and applied to the error detector and underfrequency limit.When a resistive (unity