Inverter Operation
How Inverters Work:
Simply put, an inverter is an electronic device that converts low voltage DC (direct current) battery power to 115 volt (or 230 volt internationally) AC (alternating current) household electrical power. Hand-held inverters can be plugged into any vehicle cigarette lighter outlet, producing output power levels ranging from 50 to 250* watts. Larger, high output inverters can be hard wired directly to a DC battery source and deliver power from 800 to 2500 watts.
* Intermittent operation only. Over 150 watts continuous requires direct connection to the 12 (or 24) volt power source.
Principle of Operation:
Most inverters convert DC power in two stages. The first stage is a DC-to-DC converter that raises the low voltage DC at the inverter input to 145 volts DC. The second stage is the actual inverter stage. It converts the high voltage DC into 115 volts, 60 Hz AC (230 volt, 50 Hz internationally).
The DC-to-DC converter stage uses modern high frequency power conversion techniques that eliminate the bulky transformers found in inverters based on older technology. The inverter stage uses advanced power MOSFET transistors in a full bridge configuration. This gives you excellent overload capability and the ability to operate tough reactive loads like lamp ballast's and small induction motors.
How to Calculate Wattage to Determine Inverter Size.
Most inverters currently on the market range in size from 50 watts up to 2500 watts. In determining the correct size, the actual wattage draw of the products being operated from the inverter must be determined. Many appliances and power tools will have the wattage draw stamped right on their back panel.
For those appliances that do not, the wattage amount will have to be calculated.
This is done using a very simple formula:
Volts x Amps = Watts
For example if a microwave is rated at 7 amps @ 115 volts, then the wattage draw of this unit will be 805 watts. An inverter rated on a continuous wattage output level of at least 800 watts will be necessary for operating such an item. If there is a possibility that the microwave and another item will be operating at the same time, then the wattage of each item can be added together to determine the inverter size.
Inverter Installation
Power Source
The power source you wish to connect your inverter to must provide between 10 and 15 volts DC for 115 volt models or between 20 and 30 volts DC for 230 volt models, and must be able to supply sufficient current to operate the load. The power source may be a battery or a well regulated DC power supply. As a rough guideline, divide the power consumption of the load (in watts) by 10 to obtain the current (in amperes) the power source must deliver.
Example: Load is rated at 100 watts. Power source must be able to deliver 100 10 = 10 amperes.
The unit must be connected only to batteries with a nominal output voltage of 12 (or 24) volts. The unit will not operate from a 6 volt battery. Any Statpower brand inverter model built for 12 volt input will suffer internal circuitry damage if it is connected to a 24 volt battery.
Hand-Held Inverters:
Most hand-held inverter products are equipped with a cigarette lighter plug for connection to the power source. The tip of the plug is the positive, the side contact is the negative. Insert the plug into the cigarette lighter socket in a vehicle or into the cigarette lighter socket on a battery pack to connect to the DC power source. Some higher power hand-held applications will require direct connection to the DC power source. This is required for continuous loads >150 watts.
Reverse polarity connection will damage the inverter
If the inverter is connected to the incorrect polarity, an internal fuse will open. If the unit does not function after replacement of the fuse, the unit must be returned to the manufacturer for repair.
Do not use with positive ground electrical systems
Most hand-held inverter products are designed for use with negative ground vehicle electrical systems only.
High Output Inverters:
High output inverters should be installed in a location that meets the following requirements:
1) Dry - the unit must not be allowed to come in contact with any liquids or condensing humidity.
2) Cool - ambient air temperature should be between 0 degrees C and 40 degrees C (30 degrees F and 105 degrees F) - the cooler the better.
3) Well Ventilated - allow at least 1 inch of clearance around the unit for air flow. Ensure that ventilation openings on the bottom and rear of the unit are not obstructed.
4) Safe - do not install the unit in the same compartment as batteries or in any compartment capable of storing flammable gases or fumes such as gasoline. Do not install the unit in a zero-clearance compartment
5) Close to Battery - install as close to the battery as possible (keeping item #4 in mind) in order to minimize the length of cable required to connect the inverter to the battery. It is better and cheaper to run longer AC wires than longer DC cables.
Mount the inverter unit on a flat surface using the mounting brackets on the bottom. Mounting hardware should be corrosion resistant and size #10 or larger. The unit may also be mounted horizontally or vertically if so desired.
Questions and Answers
Q: "Can I mount my inverter in a cabinet?"
A: Your inverter can be mounted in any location as long as it is clean, dry and has adequate ventilation. In general, it is best to keep your inverter as cool as possible.
Q:"Can the inverter be hooked up under the engine hood?"
A: No, the inverter is an electronic device and should not be placed in the engine compartment. Criteria for an installation location is: dry, cool, ventilated, and safe.
Q:"Can I mount my inverter under my car seat?"
A: Yes, as long as adequate ventilation is maintained. If mounting a high output inverter in this location, you must ensure that the bottom of the inverter remains unobstructed, as this is where the air intake is. If the intended mounting surface is not smooth (such as on carpeting), then you should raise that inverter with mounting blocks of some kind to increase the air flow area.
Hand-Held Inverter Trouble-Shooting
Problem: Lack of Power Output
Possible Cause:
Suggested Remedy:
Poor contact with lighter outlet
Clean out thoroughly. Replace if necessary. Spread contacts on lighter plug.
Automotive electrical system requires ignition to be on
Turn ignition key to accessory position
Cigarette lighter circuit fuse open (blown)
Check vehicle fuses, replace damaged fuse
Poor connection or inadequate wiring between battery and cigarette lighter
Repair connections and use heavier gauge wire (14 AWG min. is suggested)
Battery voltage below 10 volts
Recharge or replace battery
Load draws too much power
Reduce load to highest recommended in owner's manual
Inverter in thermal shutdown
Allow inverter to cool. Ensure there is adequate ventilation. Ensure that load is no more than maximum continuous rated for that model of inverter.
Using average reading voltmeter
Use true RMS reading meter.
Inverter is overloaded
Reduce load to maximum continuous rated to maintain regulation.
Power source voltage below 11.5 volts
Keep power source voltage above 11.5 volts to maintain regulation.
See Liability Disclosure
High Output Inverter Trouble-Shooting
Trouble-Shooting Guide:
Problem & Symptoms:
Possible Cause:
Suggested Remedy:
 Low output voltage (96 VAC to 107 VAC)
Using average reading voltmeter
 Use true RMS reading meter.
 Low output voltage and current indicator in red zone
 Reduce load
 No output voltage and voltage indicator in red zone
Low input voltage
 Recharge battery, check connections and cable
 No output voltage, no voltage indication
Inverter switched off
 No power to inverter
Internal fuse open
Reverse DC polarity
 Turn inverter on.

 Check wiring to inverter.

 Have qualified service technician check and replace fuse.
 Observe correct polarity.
 No output voltage, voltage indicator in upper red zone
 High input voltage
 Make sure that the inverter is connected to 12V battery (24V where applicable), check regulation of charging system. Should be <15V (or 30V where applicable)
 Low battery alarm on all the time, voltage indicator below 11V (22V for 24V versions)
 Poor DC wiring, poor battery condition, large load
 Use proper gauge cable and make solid connections. Use new battery. Reduce load.
 No output voltage, OVERTEMP indicator on, load in excess of maximum continuous rated input current
 Thermal shutdown
 Allow the inverter to cool off. Reduce load if continuous operation required.
 No output voltage, OVERTEMP indicator on, load less than maximum continuous rated input current
 Thermal shutdown
 Improve ventilation, make sure ventilation openings in inverter chassis are not obstructed, reduce ambient temperature.
 No output voltage, OVERLOAD indicator is on.
 Short circuit or wiring error
Very high power load
 Check AC wiring for short circuit or improper polarity (hot and neutral reversed)
 Remove load
"I have my inverter mounted in a storage box, and on hot days the overtemp warning comes on. What can I do?"
Keeping the inverter as cool as possible is very important to ensuring proper operation. If it consistently keeps going into thermal overload, you should change the mounting location to increase airflow and ventilation.
See Liability Disclosure
Common Problems
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Buzzing in some inexpensive audio systems

Interference with TV signals on some channels
The following steps may help alleviate the problem:

) Position the inverter as far as possible from the television, the antenna and the antenna cables. Use an extension cord to move the inverter away from the TV.

2) Adjust the orientation of the inverter, the antenna cables, and the TV power cord to minimize interference.

3) Make sure that the antenna feeding the TV provides an adequate ("snow free") signal and that high quality, shielded antenna cable is used.
POWER INVERTERS CAN BE VERY DANGEROUS IF NOT SELECTED, USED, INSTALLED OR MAINTAINED PROPERLY. A QUALIFIED ELECTRICAL PROFESSIONAL SHOULD BE CONTACTED FOR ADVICE. CONTACT WITH HIGH VOLTAGE COULD RESULT IN INJURY, DEATH AND RISK OF FIRE. This information is for your informational purposes only and is NOT given here as advice by RadioProShop, DCS Industries nor it's owners. We are not responsible or liable for any damage, injury, property loss or factory warranty issues in any way.
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