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Table 3-1. - Types of Portable Generators

Alternating current | |||||||

Frequency | 60-hertz | ||||||

Voltage | 120 | 120/208 | 120/208 240/416 | ||||

Phase | 1 | 1 & 3 | 3 | ||||

Wires | 2 | 4* | 4 | ||||

Fuel | G | D | G | D | G | D | |

kW Rating | |||||||

5 | X | X | X | X | |||

10 | X | X | |||||

15 | X | X | |||||

30 | X | X | |||||

60 | X | X | |||||

100 | X | X | |||||

200 | X |

G - Gasoline driven.

D - Diesel driven.

* - Panel connections permit, at rated kW output: 120/208V

3-phase 4-wire, 120V 3-phase 3-wire, 120V single-phase

2-wire, 120/240V single-phase 3 wire.

Before any part of the system can be designed, the amount of power to be transmitted, or the electrical load, must be determined. Electrical loads are generally measured in terms of amperes. kilowatts, or kilovoltamperes. In general, electrical loads are seldom constant for any appreciable time, but fluctuate constantly. In calculating the electrical load, you must determine the connected load first. The connected load is the sum of the rated capacities of all electrical appliances, lamps, motors, and so on, connected to the wiring of the system. The maximum demand load is the greatest value of all connected loads that are in operation over a specified period of time. Knowledge of the maximum demand of groups of loads is of great importance: because it is the group maximum demand that determines the size of generators, conductors, and apparatus throughout the electrical system.

The ratio between the actual maximum demand and the connected load is called the DEMAND FACTOR. If a group of loads were all connected to the supply source and drew their rated loads at the same time, the demand factor would be 1.00. There are two main reasons why the demand factor is usually less than 1.00. First, all load devices are seldom in use at the same time and, even if they are, they will seldom reach maximum demand at the same time. Second, some load devices are usually slightly larger than the minimum size needed and normally draw less than their rated load. Since the maximum demand is one of the factors determining the size of conductors, it is important that the demand factor be established as closely as possible.

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