Samlexpower PST-1500-12 Owner's Manual - Section 5 |
16 | SAMLEX AMERICA INC.
5.1 GENERAL
TheseinvertersconvertDCbatteryvoltagetoACvoltagewithanRMS(RootMean
Square)valueof120VAC,60HzRMS.
5.2 PURE SINE WAVE OUTPUT WAVEFORM
The waveform of the AC voltage is a pure Sine Waveform that is same as the waveform
ofGrid/Utilitypower (Supplementary information on pure Sine Waveform and its
advantages are discussed in Sections 2.2 to 2.4).
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”=+169.68V,slowlydropsto0V,changesthe
polaritytoNegativedirectionandslowlyincreasesintheNegativedirectiontoapeak
Negativevalue“Vpeak”=-169.68Vandthenslowlydropsbackto0V.Thereare60such
cycles in 1 sec. Cycles per second is called the “frequency” and is also termed “Hertz (Hz)”.
TheTimePeriodof1Cycleis16.66ms.
TIME
0V
Peak Negative Voltage
- V
PEAK
= - 169.68V
V
RMS
= 120 VAC
Peak Positive Voltage
+ V
PEAK
= + 169.68V
Voltage (+)
Voltage (
–)
16.66 ms
Fig. 5.1: 120 VAC, 60 Hz Pure Sine Waveform
5.3 PRINCIPLE OF OPERATION
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.