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Invertors - Diffrent types available


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In any solar installation, your Invertor might be the single most important part.


Invertor is the device that will convert your DC solar and/or battery power to 230V AC so you can use normal AC devices.


There is 3 types of invertor outputs:

Square wave, Modified wave and Sine wave.


Square wave is the cheapest to buy, but due to the output waveform, can cause loads of noise in your 230V AC devices and some of them can even overheat, like motors. Ideal for mobile solutions like in your car.


Modified wave is similar to square wave, but they might have more steps, normally 4 or so, to create an output wave more similar to sine wave. Ideal for lights and equipment that have build-in power supplies.

Could create noise on computer and TV equipment.


Sine wave is the best but also the most expensive.


Normal Invertor, Bi-Directional, Grid-Tied and Hybrid.

A normal invertor will take your DC and convert it to 230V AC.


Bi-Directional. This invertor will normally be connected to your home AC supply and to a DC supply.

Under normal operation it will use the DC supply to power the output load.

If the DC supply drops too low, like at night, it will use your home AC supply to charge the DC supply again.

Basically it functions like a UPS.

These invertors will normally have a built-in battery charger circuit, but not a Solar controller.

DC voltage is in the range of 12V DC to 48V DC.

The DC voltage have to be specified when the unit is ordered and can NOT be changed afterwards.


Grid-Tied. These are most common in Europe, as no batteries is required. They will use the Eskom grid is "batteries".

When there is an oversupply of DC power, it will put power back onto the Eskom grid, so your meter will run in reverse.

During the night when no solar is available, it will use power from the grid as per normal.

These invertors will normally have one or two solar regulators build-in.

Solar voltage is in the range of 100V DC to 500V DC.

Due to the fact that it is directly connected to the Eskom supply, there is loads of regulations concerning installing these.

Also, they will NOT switch on during a power failure.

This is to prevent killing Eskom workers servicing equipment.


Hybrid. I have just learned about this one a few days ago.

It is basically a combination of Bi-Directional and Grid-tied.

So it would be connected directly to the grid, have build-in solar regulator and battery charger.


Power rating.

Invertors will normally be rated in kVA.

This is normally the max power the device can deliver 24/7.

When working with motors, like pool pumps and such, please make sure that you have enough to start the pump.

When a motor is started, it can use as much as 6 times the rated power on the motor to start. So a 1kW pump might use 6kW in a couple of seconds to start.



Every invertor have an efficiency rating. This can be anything from 80% to 98%. In any solar system this can be extremely important.

Basically this rating will tell you how much of your input power is converted to output power, so the higher this rating, the more efficient the invertor is working.

Also note that efficiency can vary according to the output power.

So a 1kVA invertor could be 90% efficient at 50% output and 96% at 100% output.



Also take note of this one.

Normally this is a given ambient temperature the unit can operate in. For every degree higher than said temp, the unit must be derated by said %.

In winter I think this might not affect us so much, but definitely in summer, so be aware of where you will be mounting the invertor to keep it as cool as possible.


Hope this helps.



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