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Generally, the power rating of an electrical appliance indicates the amount of work that can be done by it.
The electric power required for operating an electrical appliance is not always equal to the output wattage
of the appliance. The electrical appliances generally have a label showing their rated voltage, frequency,
and power consumption (input wattage). The power consumption of an electrical appliance is the power
necessary for using it. When using a generator for operating an electrical appliance, the power factor and
starting wattage must be taken into consideration.
In order to determine the right size generator, it is necessary to add the total wattage of all appliances to
be connected to the unit.
Refer to the followings to calculate the power consumption of each appliance or equipment by its type.
(1) Incandescent lamp, heater, etc. with a power factor of 1.0
Total power consumption must be equal to or less than the rated output of the generator.
Example : A rated 3000W generator can turn thirty 100W incandescent lamps on.
(2)
Fluorescent lamps, motor driven tools, light electrical appliances, etc. with a smaller power factor
Select a generator with a rated output equivalent to 1.2 to 2 times of the power consumption of the
load. Generally the starting wattage of motor driven tools and light electrical appliances are 1.2 to 3
times lager than their running wattage.
Example : A rated 250 W electric drill requires a 400 W generator to start it.
NOTE 1: If a power factor correction capacitor is not applied to the fluorescent lamp, the more power
shall be required to drive the lamps.
NOTE 2: Nominal wattage of the fluorscent lamp generally indicates the output wattage of the lamp.
Therefore, if the fluorescent lamp has no special indication as to the power consumption,
efficiency should be taken into account as explained in ltem (5) on the following page.
(3) Mercury lamps with a smaller power factor
Loads for mercury lamps require 2 to 3 times the indicated wattage during start-up.
Example : A 400 W mercury lamp requires 800 W to 1200 W power source to be turned on. A rated
3000 W generator can power two or three 400 W mercury lamps.
(4) Initially loaded motor driven appliances such as water pumps, compressors, etc.
These appliances require large starting wattage which is 3 to 5 times of running wattage.
Example : A rated 900 W compressor requires a 4500 W generator to drive it.
NOTE 1: Motor-driven appliances require the aforementioned generator output only at the starting.
Once their motors are started, the appliances consume about 1.2 to 2 times their rated power
consumption so that the excess power generated by the generator can be used for other
electrical appliances.
NOTE 2: Motor-driven appliances mentioned in items (3) and (4) vary in their required motor starting
power depending on the kind of motor and start-up load. If it is difficult to determine the
optimum generator capacity, select a generator with a larger capacity.
3. RANGE OF APPLICATIONS