Samlexpower SI-A1-VR1500 Owner's Manual - 2．

2．

HOW YOUR INVERTER WORKS 

The inverter converts low voltage DC (Direct Current) from a battery or other 

power source to 115 volt AC (Alternating Current) household power. 

PRINCIPLE OF OPERATION 

The inverter converts power in two stages. The first stage is a DC to DC 

conversion process that raises the low voltage DC at the inverter input to 

higher volts DC. The second stage is the actual inverter stage that converts the 

high voltage DC into 115 volts, 60 Hz AC(rms). The DC-to-DC converter stage 

uses modern high frequency power conversion techniques that have replaced 

the bulky transformers found in less technologically-advanced models. The 

inverter stage uses advanced power MOSFET transistors in a full bridge 

configuration. 

THE OUTPUT WAVEFORM 

The AC output waveform of the VR-series inverter is known as “modified sine 

wave”. It is a waveform that has characteristics similar to the sine wave shape 

of utility power. This type of waveform is suitable for most AC loads, including 

linear and switching power supplies used in electronic equipment, 

transformers, and motors. (See Figure 4).   

The modified sine wave produced by the VR-series inverter has an RMS (root 

mean square) voltage of 115 volts, which is the same as standard household 

power. Most AC voltmeters (both digital and analog) are sensitive to the 

average value of the waveform rather than the RMS value. They are calibrated 

for RMS voltage under the assumption that the waveform measured will be a 

pure sine wave. These meters will not read the RMS voltage of a modified sine 

wave correctly. They will read about 20 to 30 volts low when measuring the 

output of the inverter. For accurate measurement of the output voltage of this 

unit, use a true RMS reading voltmeter such as a Fluke 87III, Fluke 8060A, 

Fluke 77/99 series or Beckman 4410. 

FIGURE 4 :    Modified Sine Wave and Sine Wave Comparison 

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