Samlexpower PST-1000-12 Owner's manual - Section 5 |
14 | SAMLEX AMERICA INC.
seCtIOn 5 |
Principle of Operation
TheseinvertersconvertDCbatteryvoltagetoACvoltagewithanRMS(RootMean
Square)valueof120VAC,60HzRMS.
ThewaveformoftheACvoltageisapuresinewaveformthatissameasthewaveform
of grid power (Supplementary information on pure sine waveform and its advantages
are discussed on pages 8 & 9).
fig.5.1belowspecifiesthecharacteristicsof120VAC,60Hzpuresinewaveform.The
instantaneous value and polarity of the voltage varies cyclically with respect to time. for
example,inonecycleina120VAC,60Hzsystem,itslowlyrisesinthepositivedirection
from0Vtoapeakpositivevalue“Vpeak”=+168.69V,slowlydropsto0V,changesthe
polaritytonegativedirectionandslowlyincreasesinthenegativedirectiontoapeak
negativevalue“Vpeak”=-168.69Vandthenslowlydropsbackto0V.Thereare60such
cyclesin1sec.Cyclespersecondiscalledthe“frequency”andisalsotermed“Hertz
(Hz)”.
Fig. 5.1: 120 VAC, 60 Hz Pure Sine Waveform
Thevoltageconversiontakesplaceintwostages.Inthefirststage,theDCvoltage
ofthebatteryisconvertedtoahighvoltageDCusinghighfrequencyswitchingand
PulseWidthModulation(PWM)technique.Inthesecondstage,thehighvoltageDCis
convertedto120VAC,60HzsinewaveACagainusingPWMtechnique.Thisisdoneby
usingaspecialwaveshapingtechniquewherethehighvoltageDCisswitchedatahigh
frequency and the pulse width of this switching is modulated with respect to a refer-
ence sine wave.
TIME
OV
+
-
-V
PEAK
= - 168.69V
+V
PEAK
= + 168.69V
V
RMS
= 120 VAC