How Your Inverter Works; Principle Of Operation; The Output Waveform - SamplexPower SAM-250-12 Owner's Manual

HOW YOUR INVERTER WORKS

The inverter converts low voltage DC (Direct Current) from a battery or other power source to
standard 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 150 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 SAM 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 1).
The modified sine wave produced by the 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 1 : Modified Sine Wave and Sine Wave Comparison
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