Calculating Power Required to Run Equipment -

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Calculating Power Required to Run Equipment
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Calculating Power Required to Run Equipment

Load analysis and generator sizing are essential for satisfactory generator
and equipment operation. The available auxiliary power is limited by engine
horsepower and is a small, finite power system as compared to the large,
seemingly-infinite electric utility system. Any single load may represent usage
of a large portion of the total power available. It is necessary to carefully
determine the total load that will be applied by adding up all the individual
loads. Some tools are rated in watts, others in amperes. Lights and heaters
are rated in watts. Most equipment will specify on its nameplate what its
specific requirements will be.

For example, a drill requires 4.5 amperes at 115 volts. Watts equals volts
times amperes. Therefore, this drill requires approximately 520 watts. Add
three 200 watt flood lamps, and requirements increase by 600 watts for a
total of 1120 watts. Continue in this fashion until all loads have been added.
Be sure to add all motor running requirements to the total. Consider also that
a load is not always constant. To be sure, lights and resistance heaters are
constant, but portable power tools are not. One rarely grinds or drills with
a consistent, even pressure. Thus, the load requirement changes may be
greater than anticipated.

This equation provides an actual power requirement for resistive loads, or an approximate running requirement for non-restrictive loads

EXAMPLE 1: If a drill requires 4.5 amperes at 115 volts, calculate its running power requirements in watts.

115 V x 4.5 A = 520 W

Therefore, the individual load applied by the drill is 520 watts.

EXAMPLE 2: If a flood lamp is rated at 200 watts, the individual load applies by the lamp is 200 watts. If three 200 watt flood lamps are used with the drill in example 1, add the individual loads to calculate total load.

(200 W + 200 W + 200 W) + 520 W = 1120 W

Therefore, total load applied by the three flood lamps and drill is 120 watts.

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