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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
179, Fluke 79 III series, Beckman 4410, or Triplett 4200.
Modified Sine Wave and Sine Wave Comparison
PROTECTIVE FEATURES OF THE INVERTER
The Power Inverter monitors the following potentially hazardous conditions:
Low Battery Voltage —
This condition is not harmful to the inverter, but could damage
the power source. An alarm will sound when input voltage drops below 11 volts. The
Power Inverter automatically shuts down when input voltage drops below 10 volts.
When the condition is corrected, the inverter can be reset by turning OFF, then back
ON.
Over Voltage Protection —
The Power Inverter will automatically shutdown when the
input voltage exceeds 15.5 volts DC.
Overload Protection —
The unit will automatically shut down when the continuous
draw exceeds 750 watts. Reduce the load and manually reset using the inverter’s
ON/OFF Pushbutton.
Over Temperature Protection —
If the temperature inside the Power Inverter reaches
150°F, the unit will automatically shut down. Allow the unit to cool for at least 15
minutes before restarting after a heat-related shutdown. Unplug the unit while cooling.
If the low voltage alarm sounds when the battery is fully charged, follow the steps
outlined in the “Troubleshooting” section of this User’s Manual. The alarm will sound
if there is an excessive voltage drop between the battery and the inverter.
Notes:
It is normal for the alarm to sound while the unit is being connected to, or
disconnected from, the power source. This is not indicative of a problem.
Reverse polarity or short circuit condition may cause external or internal fuses
to open and may cause irreversible damage to the Power Inverter. Take extra
care to ensure a proper polarity hook-up.
INSTALLATION AND OPERATING INSTRUCTIONS
Power Source Requirements
The power source must provide a nominal voltage of 12.5 volts DC and must be able
to supply the necessary current to operate the load. The power source may be a
battery or a well-regulated DC power supply. To obtain a rough estimate of the current
(in amperes) the power source must deliver, simply divide the power consumption of
the load (in watts AC) by 10.
Example: If a load is rated at 750 watts AC, the power source must be able to deliver:
750 divided by 10 = 75 amperes.
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inverter, the red LED indicates inverter shutdown from an over-load or over-
temperature fault and the yellow LED indicates an input fault. In addition to turning
the unit ON and OFF, the ON/OFF Pushbutton can be used to force reset of the
inverter circuits.
Figure 3 Top Panel
HOW THIS INVERTER WORKS
The power 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 145 volts DC. The
second stage is the actual inverter stage that converts the high voltage DC current into
115 volts, 60 Hz AC current.
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. This ensures excellent overload capacity.
The Power Inverter Output Waveform
The AC output waveform of the Power 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.
The modified sine wave produced by the Power 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
12VDC to
145VDC
CONVERSION
145VDC to
115VAC
CONVERSION
Internal
Fuses
AC
Outlet
12VDC
Input
115VAC, 60Hz
to AC appliances
ON/OFF
PUSHBUTTON
OUTPUT FAULT
INPUT FAULT
POWER
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