Samlex Power PST-600-12 Manuel Du Propriétaire page 9

Section 2 | General information
Power Factor, (PF): It is denoted by "Pf" and is equal to the ratio of the Active Power
(P) in Watts to the Apparent Power (S) in VA. The maximum value is 1 for resistive types
of loads where the Active Power (P) in Watts = the Apparent Power (S) in VA. It is 0 for
purely inductive or purely capacitive loads. Practically, the loads will be a combination of
resistive, inductive and capacitive elements and hence, its value will be > 0 <1. Normally
it ranges from 0.5 to 0.8 e.g. (i) AC motors (0.4 to 0.8), (ii) Transformers (0.8) (iii) AC to
DC Switch Mode Power Supplies (0.5 to 0.6) etc.
Load: Electrical appliance or device to which an electrical voltage is fed.
Linear Load: A load that draws sinusoidal current when a sinusoidal voltage is fed to it.
Examples are, incandescent lamp, heater, electric motor, etc.
Non-Linear Load: A load that does not draw a sinusoidal current when a sinusoidal volt-
age is fed to it. For example, non-power factor corrected Switched Mode Power Supplies
(SMPS) used in computers, audio video equipment, battery chargers, etc.
Resistive Load: A device or appliance that consists of pure resistance (like filament
lamps, cook tops, toaster, coffee maker etc.) and draws only Active Power (Watts) from
the inverter. The inverter can be sized based on the Active Power rating (Watts) of
resistive type of loads without creating overload (except for resistive type of loads with
Tungsten based heating element like in Incandescent Light Bulbs, Quartz Halogen Lights
and Quartz Halogen Infrared Heaters. These require higher starting surge power due to
lower resistance value when the heating element is cold).
Reactive Load: A device or appliance that consists of a combination of resistive, inductive
and capacitive elements (like motor driven tools, refrigeration compressors, microwaves,
computers, audio/ video etc.). The Power Factor of this type of load is <1 e.g. AC motors
(PF=0.4 to 0.8), Transformers (PF=0.8), AC to DC Switch Mode Power Supplies (PF=0.5
to 0.6) etc. These devices require Apparent Power (VA) from the AC power source. The
Apparent Power is a vectorial sum of Active Power (Watts) and Reactive Power (VAR).
The AC power source has to be sized based on the higher Apparent Power (VA) and also
based on the Starting Surge Power.
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