PSE-12275A Manual
30 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 31
SECTION 8 | Principal of Operation
DEVICES THAT MAY NOT OPERATE ON MODIFIED SINE WAVE
The output wave form of these inverters is a modied sine wave (see Fig. 8.1, page 30).
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 modied sine
wave, the voltage rises and falls abruptly, the phase angle also changes abruptly and
it sits at 0 Volts 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) does not work properly.
Also, as the modied 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 modied
sine wave. For example, a 60Hz modied sine wave will consist of sine waves with odd
harmonic frequencies of 3rd (180Hz), 5th (300Hz), 7th (420Hz) and so on. The high fre-
quency harmonic content produces enhanced radio interference, higher heating effect
in motors / microwaves and produces overloading due to lowering of the impedance of
low frequency lter capacitors / Power Factor improvement capacitors.
NOTE: Electric motors and microwaves will run Hotter when operated with modied
sine wave. Please ensure proper ventilation for adequate cooling.
Some examples of devices that may not work properly with modied sine wave and may
also get damaged are given below:
- The built-in clocks in devices such as clock radios, alarm clocks, coffeemakers, bread-
makers, VCR, microwave ovens etc may not keep time correctly.
- Output voltage control devices like dimmers, ceiling fan / motor speed control may
not work properly (dimming / speed control may not function).
- Transformer-less capacitive input powered devices like (i) Razors, ashlights, night-
lights, smoke detectors etc (ii) Re-chargers for battery packs used in hand power
tools. These may get damaged. Please check with the manufacturer of these types of
devices for suitability.
- Devices that use radio frequency signals carried by the AC distribution wiring.
- Oil burner primary controls / some new furnaces with microprocessor controls
- High intensity discharge (HID) lamps like Metal Halide lamps. These may get dam-
aged. Please check with the manufacturer of these types of devices for suitability.
- Some ourescent lamps that have Power Factor correction capacitors. The inverter
may shut down indicating overload.
- Sewing machines with speed / microprocessor control.