Samlex America PST-200S-24E - Manual (Page 8)

8 | SAMLEX AMERICA INC.
the inverter. The inverter can be sized based on the Active Power rating (Watts) without
creating overload.
Reactive Load: A device or appliance that consists of a combination of resistive, induc-
tive and capacitive elements (like motor driven tools, refrigeration compressors, micro-
waves, computers, audio/ video etc.). These devices require Apparent Power (VA) from
the inverter to operate. The Apparent Power is a vectorial sum of Active Power (Watts)
and Reactive Power (VAR). The inverter has to be sized based on the higher Apparent
Power (VA).
output Voltage Waveforms
Fig. 2.1: Pure and Modified Sine Waveforms
The output waveform of the Samlex PST Series inverters is a pure sine wave like the
waveform of the grid power. Please see sine wave represented in the fig. 2.1 that also
shows modified waveform for comparison.
In a sine wave, the voltage rises and falls smoothly with a smoothly changing phase
angle and also changes its polarity instantly when it crosses 0 Volts. In a modified sine
wave, the voltage rises and falls abruptly, the phase angle also changes abruptly and
it sits at 0Vs for some time before changing its polarity. Thus, any device that uses a
control circuitry that senses the phase (for voltage / speed control) or instantaneous zero
voltage crossing (for timing control) will not work properly from a voltage that has a
modified sine waveform.
Also, as the modified sine wave is a form of square wave, it is comprised of multiple
sine waves of odd harmonics (multiples) of the fundamental frequency of the modified
sine wave. for example, a 50 Hz modified sine wave will consist of sine waves with odd
harmonic frequencies of 3rd (150 Hz), 5th (250 Hz), 7th (350 Hz) and so on. The high
seCtIOn 2 | General Information
TIME
360
320
280
240
200
160
120
80
40
0
40
80
120
160
200
240
280
320
360
Modified Sine
Wave sits at
ZERO for some
time and then
rises or falls
Modified Sine Wave
Sine Wave
Pure Sine Wave
crosses 0.0V
instantaneously