Uninterruptible Power Supplies and Standby Power Systems
Written by two experienced engineers, this book covers rotary UPS systems and battery selection, and offers complete, up-to-date guidance on design, installation, operation, and maintenance.
TABLE OF CONTENTS Uninterruptible Power Supplies and Standby Power Systems
Chapter 3: Additional Information Relating to the Standby Supply Installation
Introduction
This chapter is concerned with various matters which do not fit comfortably into either of the two previous chapters. The calculation of engine and generating ratings is a somewhat tortuous exercise and has been left until this late stage in the book so that the reader has the benefit of text appearing in earlier parts of the book. The components of the load current, characteristics of particular loads, vibration, and noise are discussed.
In this chapter the expressions kWm and kWe are used to denote mechanical and electrical power respectively.
Sizing the Engine and Generator
The Power Rating of the Engine
The factors to be considered in sizing the engine are:
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The class of power rating specified for the generating set (continuous power, prime power, or limited time running power)
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The frequency performance class G1, G2, G3, G4, or as otherwise specified (see Table 1.1)
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The maximum load (kWm) to be supplied
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The maximum step of load (kWm) to be applied
The engine must be capable of supplying the total required mechanical load to the generator. This will be higher than the electrical load which the set is intended to supply, the additional loads to be considered being:
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The losses within the generator, which may be 5 or 6 percent
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The radiator fan if it is not engine driven
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Any electrically driven ventilation fans, engine room lighting, etc., that are not included in the load to be supplied
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Any engine...
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