Samlexpower Evolution Series - Section 1.3; General Information - Inverter Related

12 | SAMLEX AMERICA INC.
1.3 GENERAL INFORMATION - INVERTER RELATED
General information related to operation and sizing of inverters is given in succeeding sub-sections.
1.3.1 AC Voltage Waveforms
TIME
180
160
140
120
100
80
60
40
20
0
20
40
60
80
100
120
140
160
180
Modied Sine
Wave sits at
ZERO for some
time and then
rises or falls
Pure Sine Wave
crosses zero V
instantaneously
Modied Sine Wave
• V
RMS
= 120V
• V
peak
= 140 to 160V
Sine Wave
• V
RMS
= 120VAC
• V
peak
= 169.68V
16.66 ms
VOLTS − VOLTS +
V
peak
= 169.68V
V
peak
= 140 to 160V
V
RMS
= 120 VAC
Fig 1.3.1 Pure and Modied Sine Waveforms for 120V, 60 Hz
The 120V output waveform of the Evolution
™
series inverters is a Pure Sine Wave like the waveform of Utility / Grid
power. Please see Sine Waveform represented in the Fig. 1.3.1 that also shows equivalent Modied 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 Modied Sine Wave, the voltage rises and falls abruptly, the phase
angle also changes abruptly and it sits at 0V 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 Modied Sine Waveform.
Also, as the Modied 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 Modied Sine Wave. For example, a 60 Hz Modied
Sine Wave will consist of Sine Waves with odd harmonic frequencies of 3rd (180 Hz), 5th (300 Hz), 7th (420 Hz)
and so on. The high frequency harmonic content in a Modied Sine Wave produces enhanced radio interference,
higher heating effect in inductive loads like microwaves and motor driven devices like hand tools, refrigeration
/ air-conditioning compressors, pumps etc. The higher frequency harmonics also produce overloading effect in
low frequency capacitors due to lowering of their capacitive reactance by the higher harmonic frequencies. These
capacitors are used in ballasts for uorescent lighting for Power Factor improvement and in single-phase induction
motors as start and run capacitors. Thus, Modied and Square Wave Inverters may shut down due to overload
when powering these devices.
SECTION 1.3 | General Information – Inverter Related