Samlexpower PST-1500-12 Owner's Manual - Section 2 |
8 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 9
Power Factor, (PF): It is denoted by “Pf” and is equal to the ratio of the Active Power
(P)inWattstotheApparentPower(S)inVA.Themaximumvalueis1forresistivetypes
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,inductiveandcapacitiveelementsandhence,itsvaluewillbe>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
DCSwitchModePowerSupplies(0.5to0.6)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.
Examplesare,incandescentlamp,heater,electricmotor,etc.
Non-Linear Load: A load that does not draw a sinusoidal current when a sinusoidal volt-
ageisfedtoit.Forexample,non-powerfactorcorrectedSwitchedModePowerSupplies
(SMPS) used in computers, audio video equipment, battery chargers, etc.
Resistive Load:Adeviceorappliancethatconsistsofpureresistance(likefilament
lamps,cooktops,toaster,coffeemakeretc.)anddrawsonlyActivePower(Watts)from
the inverter. The inverter can be sized based on the Active Power rating (Watts) of
resistivetypeofloadswithoutcreatingoverload(exceptforresistivetypeofloadswith
TungstenbasedheatingelementlikeinIncandescentLightBulbs,QuartzHalogenLights
andQuartzHalogenInfraredHeaters.Theserequirehigherstartingsurgepowerdueto
lower resistance value when the heating element is cold).
Reactive Load: A device or appliance that consists of a combination of resistive, inductive
andcapacitiveelements(likemotordriventools,refrigerationcompressors,microwaves,
computers,audio/videoetc.).ThePowerFactorofthistypeofloadis<1e.g.ACmotors
(PF=0.4to0.8),Transformers(PF=0.8),ACtoDCSwitchModePowerSupplies(PF=0.5
to0.6)etc.ThesedevicesrequireApparentPower(VA)fromtheACpowersource.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.