Samlexpower PST-15S-12E Owner's manual - Section 5 |
16 | SAMLEX AMERICA INC.
5.1 GeneRAL
These inverters convert DC battery voltage to AC voltage with an RMS (Root Mean
Square) value of 230 VAC, 60 Hz.
5.2 PURe Sine WAVe oUtPUt WAVeFoRM
The waveform of the AC voltage is a pure Sine Waveform that is same as the waveform
of Grid / Utility power (Supplementary information on pure Sine Waveform and its
advantages are discussed in Sections 2.2 to 2.4).
fig. 5.1 below specifies the characteristics of 230 VAC, 50 Hz/60 Hz pure Sine Waveform.
The instantaneous value and polarity of the voltage varies cyclically with respect to time.
for example, in one cycle in a 230 VAC, 50 Hz/60 Hz system, it slowly rises in the Positive di-
rection from 0V to a peak Positive value “Vpeak” = + 325.22V, slowly drops to 0V, changes
the polarity to Negative direction and slowly increases in the Negative direction to a peak
Negative value “Vpeak” = - 325.22V and then slowly drops back to 0V. There are 50 such
cycles in 1 sec in 50 Hz and 60 in 60 Hz. Cycles per second is called the “frequency” and is
also termed “Hertz (Hz)”. The Time Period of 1 Cycle is 20.00 ms for 50 Hz and 16.66 ms
for 60 Hz.
TIME
0V
Peak Negative Voltage
- V
PEAK
= - 325.22V
V
RMS
= 230 VAC
Peak Positive Voltage
+ V
PEAK
= + 325.22V
Voltage (+)
Voltage (
–)
20.00 ms for 50 Hz
16.66 ms for 60 Hz
Fig. 5.1: 230 VAC, 50/60 Hz Pure Sine Waveform
5.3 PRinciPLe oF oPeRAtion
The voltage conversion takes place in two stages. In the first stage, the DC voltage of
the battery is converted to a high voltage DC using high frequency switching and Pulse
Width Modulation (PWM) technique. In the second stage, the high voltage DC is con-
verted to 230 VAC, 50/60 Hz sine wave AC again using PWM technique. This is done by
using a special wave shaping technique where the high voltage DC is switched at a high
frequency and the pulse width of this switching is modulated with respect to a refer-
ence sine wave.