Guardian Technologies 4758, 4456, 4390, 4389, 4760 Section, Operational Analysis, Part, Introduction

SECTION 4.2

OPERATIONAL ANALYSIS

PART 4

DC CONTROL

INTRODUCTION

This "Operational Analysis" is intended to familiarize the service technician with the operation of the DC control system on prepackaged units with air-cooled engine. A thorough understanding of how the system works is essential to sound and logical troubleshooting. The DC control system illustrations on the following pages include a "V- Type" prepackaged transfer switch.

UTILITY SOURCE VOLTAGE AVAILABLE

See Figure 1, above. The circuit condition with the AUTO-OFF-MANUAL switch set to AUTO and with "Utility" source power available can be briefly described as follows:

"Utility" source voltage is available to transfer switch terminal lugs N1/N2. With the transfer switch main contacts at their "Utility" side, this source voltage is available to terminal lugs T1/T2 and to the "Load" circuits.

"Utility" voltage is delivered to the primary winding of a sensing transformer (TX), via transfer switch wires N1/N2, fuses F1/F2, connected wiring, and Control Panel "Utility 1/Utility 2" terminals. A resultant voltage (about 16 volts AC) is induced into the transformer secondary windings and then delivered to the circuit board via Wires 224/225. The circuit board uses this reduced "Utility" voltage as sensing voltage. Wires 224A/225A supply 16 VAC to the battery charger.

Figure 1. Circuit Condition - Utility Source Voltage Available

Battery output is delivered to the circuit board with the AUTO-OFF-MANUAL switch (SW1) set to AUTO, as shown.

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