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Discussion Starter #1 (Edited)
Inverters convert 12 VDC to 240 VAC using solid state electronics, the quality and price variations are considerable.

Inverter Output waveforms

Square Wave
The majority of waveforms have a trapezioal waveform this is sutibable for most types of equipment but microwaves and some inductive loads might not opperate at full optput (about 20% loss) this can be improved by the use of an auto-transformer. Lighting starts can be improved by the the instllation of a 3 microfarad capacitor across the inverter input.

Sine Wave
These units are ideal, but can be very expensive! Some units have a modified sine wave (Quasi-sine) which has more than 2 harmonics and seem to me to be the best cost/quality balance.

DC Loads
A typical inverter is capable of drawing large a large current from the battery, it is essential for the battery capacity to be able to support these loads without affecting the exiasting electrical system. A fast charge regulator should be considered when instllaling an inverter.

AC Load DC Current draw Peak Overload

200W (0.8A) 18A 42A
400W (1.6A) 37A 100A
600W (2.4A) 56A 145A
900W (3.6A) 84A 180A
1200W (4.8A) 120A 290A
2400W (9.6A) 240A 580A
3000W (12A) 300A 750A

Transfer Systems
If another AC power source is connected across the inverter output the inverter will be seriously damaged, campsite power and inverter outputs must never be paralled at any time. To remove this possibality there are two options:

Rotary Switch
I consider the rotary switch the best way to go, use a center off type with the inverter to one side and campsite power to the other.

Automatic Changeover Systems
With a bit of thought and some mechanicaly interlocking contactors an automatic changover system can be built, so when campsite power is plugged in the inverter output is disconnected and campsite connected automaticaly (Another thing to go wrong)

Auto start inverters
Lots of units now have an auto start facility, remember to include the 10-50mA draw in dc load calculations. Activation load, the load required to start most inverters is approx 6VA or greater, if your van is to be left for an extended perioid if time remember to switch off your inverter. In some cases lights are not enough to switch on inverters alone, if this is the case momentarily switch on another load.

Good ventellation is required in a clean dry instllation area allowing sufficent vertical clearance for convection of heat from the unit.

Temperature derating factors
40 to 50’C 80% rated o/p
-10 to 40’C 100% rated o/p
-10 to -20’c 130% rated o/p

Output Raiting -The rating based on a purely resistave load for a nominal perioid
Continious Raiting -The nominal countiunal raiting
Maximum Rating -The maximum short duration load

Useful Equations
Time (hours) allowed =
battery capacity (Ah) divided by load current (A)

Battery (Ah) capacity =
time (hours) required multiplied by load (A) current

Load (A) current =
power rating of appliance (W) divided by
((10 for 12 volt) or (20 for 24 volt))

Hope this helps,
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