An (inverter) is an electronic device that converts the DC voltage of a battery into AC voltage 220 volt 50 Hz.

An inverter is characterized by the following sizes:

• Input voltage: 12v , 24v, 48v
• Output voltage: For Greece it is 220V 50Hz
• Output power: in watt
• Output peak: it is the maximum power that it can instantly give for starting motors and other inductive loads.
• Output waveform: There are two forms of the pure sine and the modified sine. Pure sine is best that there is but it is much more expensive in relation to the modified.

In addition to the above, the following characteristics are very important :

Protecting the inverter to extreme changes: When starting inductive loads (eg motors, solenoids, etc.) a very large current is needed instantly for their startup. The momentary power can reach 10 times the nominal power of the device. If the power required is greater than the peak of the inverter there is a risk of immediate destruction. Some expensive inverterσ are able to be protected in such situations without being destroyed.

Saving energy: All inverters even if there is no load have significant subsistence. Therefore expensive inverters have consumption reduction system to almost zero when no there are no connected loads.

Charging capacity: Some inverter have built-in charger and automatic changeover switch.

In general you could classify the inverters in 2 categories.

1. Simple. They are low cost inverters of simple construction. They are very cheap and usually produce modified sine. They are not protected for instant changes and thus require attention during use. Also they do not carry energy saving system. These inverters are broad popular because of their low cost and can be used with excellent results if strict compliance with the instructions.
2. Expensive. These include higher power inverters, of pure sine which are protected in extreme changes (not destroyed by large inductive loads), saving energy and with very large peak output (up to three times and five times).They also bear some built-in charger and automatic changeover switch. It is the best choice for every application, but the disadvantage is the very high price.

HOW TO CALCULATE WHICH INVERTER FITS MY NEEDS?

The most simple but expensive solution is to buy an expensive inverter. These inverters have 3- to 5-fold capacity Peak and thus can easily start motors and inductive loads, but most importantly, even if you accidentally exceed the peak capacity of the inverter it is not damaged. Also they produce pure sine and thereby guaranteed service of the devices without problems.

If you do not have the money for an expensive inverter then you should buy a simple inverter calculating exactly your needs without making tests with other devices which can destroy it. Divide your loads into resistive (lamps, tv, radio, laptop, etc.) and inductive (refrigerators, pumps, office fluorescent lamps, motors, etc.) Combine all resistive loads you want to operate simultaneously. Combine all inductive loads and multiply by 10. Add up both totals. The result should not exceed the peak of the inverter otherwise there is imminent danger of destruction WARRANTY IS NOT APPLICABLE.

Example 1. I have a simple inverter of 300 watt (with a 600 watt peak), can i use it for a 100watt fridge?

Answer: A 100 watt fridge at startup may require power up to 10 times the nominal. Thus it will require 100×10=1000 watt. The inverter’s peak is only 600 watt so not only will it not start the fridge but it will be totally destroyed. In this case NO WARRANTY IS APPLICABLE.

Example 2. I have an expensive 1500 watt inverter with 5 times larger Peak (7500 watt). Can i use a 500 watt pump.

Yes, the pump will require 500×10=5000watt for its startup which is way less than 7500 watt. Even if u use a much larger pump, though, eg 1800 watt there is no reason to worry since the inverter is protected in such cases.

WARRANTY IS NOT APPLICABLE WHEN:

• Connect the inverter to the battery upside down
• You are trying to operate a device with a higher peak than what the inverter can give (only valid for simple inverters).
• Confuse the output of the inverter (220v) with another source such as electricity network or a generator.

The instantaneous power needed to start inductive loads depends on the type of cargo, construction, power factor (cosφ), loading at startup etc. In general we can take (for safety) 10 times the nominal power, but this does not mean that it cannot be smaller or even larger.