Samlexpower PST-100S-12A Owner's Manual - Modified Sine-Wave Inverter
Page 8
ADVANTAGES OF A PURE SINE-WAVE INVERTER OVER A
MODIFIED SINE-WAVE INVERTER
The output voltage of a sine-wave inverter has a sine wave-form like the sine wave-
form of the mains / utility voltage. 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 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) will
not work properly from a voltage that has a modified sine wave-form.
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 60 Hz modified sine wave will consist of sine waves
with odd harmonic frequencies of 3rd
(180 Hz), 5
th
(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 motors / microwaves and produces
overloading due to lowering of the impedance of low frequency filter capacitors /
power factor improvement capacitors.
Advantages of sine-wave inverters:
•
Theoutputwave-formisasine-wavewithverylowharmonicdistortionand
clean power like utility supplied electricity.
•
Inductiveloadslikemicrowavesandmotorsrunfaster,quieterandcooler
•
Reducesaudibleandelectricalnoiseinfans,fluorescentlights,audio
amplifiers, TV, fax and answering machines
•
Preventscrashesincomputers,weirdprintoutsandglitchesinmonitors
Some examples of devices that may not work properly with modified sine wave and
may also get damaged are given below:
•
Laserprinters,photocopiers,magneto-opticalharddrives
•
Thebuilt-inclocksindevicessuchasclockradios,alarmclocks,coffeemakers,
bread-makers, VCR, microwave ovens etc may not keep time correctly.
•
Outputvoltagecontroldeviceslikedimmers,ceilingfan/motorspeed
control may not work properly (dimming / speed control may not function)
•
Sewingmachineswithspeed/microprocessorcontrol
•
Transformer-lesscapacitiveinputpowereddeviceslike(i)Razors,flashlights,
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
•
DevicesthatuseradiofrequencysignalscarriedbytheACdistribution
wiring.
•
Somenewfurnaceswithmicroprocessorcontrol/Oilburnerprimarycontrols
•
Highintensitydischarge(HID)lampslikeMetalHalidelamps.These may get
damaged. Please check with the manufacturer of these types of devices for
suitability
•
Somefluorescentlamps/lightfixturesthathavepowerfactorcorrection
capacitors. The inverter may shut down indicating overload