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
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
Pure Sine Wave
crosses zero V
instantaneously
Modified Sine Wave
Sine Wave
16.66 ms
240 V
RMS
120 V
RMS
VOL
TS
−
VOL
TS +
V
peak
= 169.68V (for 120 V
RMS
) or, 339.36V (for 240 V
RMS
)
V
peak
= 140 to 160V (for 120 V
RMS
) or, 280-320V (for 240 V
RMS
)
V
RMS
= 120 VAC or, 240 VAC
Fig 1.3.1 Pure and Modified Sine Waveforms for 120VAC, 60 Hz / 240V, 60 Hz
The 120 / 240 VAC 60 Hz output waveform of the EVO-4248SP is a Pure Sine Wave like the waveform from Utility / Grid
power. Fig. 1.3.1 shows a Modified Waveform and Pure Sine Wave 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 0V for some time before changing its polarity. Thus, devices that use control circuitry to sense the
phase (
for voltage / speed control
) or instantaneous zero voltage crossing (
for timing control
) will not work properly when
powered with 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 of the
fundamental frequency of the Modified Sine Wave. For example, a 60 Hz Modified 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 Modified 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 fluorescent lighting for Power Factor
improvement and in single-phase induction motors as start and run capacitors. Thus, Modified and Square Wave Inverters
may shut down due to overload when powering these devices.
SECTION 1.3 |
General Information
–
Inverter Related
Summary of Contents for Evolution EVO-4248SP
Page 115: ...SAMLEX AMERICA INC 115 NOTES...
