At Gold Coast Solar Power Solutions we have been receiving a few enquiries lately from customers who have 3 phase power at their property and they’ve been told that they require a 3 phase solar inverter to suit this.

Do You Need A 3 Phase Solar Inverter?

The answer to this question really comes down to your unique situation. 3 Phase solar inverters do have some benefits but they also come at a higher cost compared to single phase solar inverters. Due to the higher cost you really want to make sure that your going to benefit from the greater expense.

What Are The Benefits Of 3 Phase Inverters?

The main benefits of 3 phase solar inverters is the fact that they convert the solar power to AC power which is fed evenly into the property over all 3 phases. For example, a 5 kW single phase solar inverter working at maximum capacity would be feeding 5kW of solar power into one phase but a three phase 5kW solar inverter in the same situation would feed the power evenly into the 3 phases. 5 kW divided by 3 phases = 1.7 kW; that’s 1.7 kW of power feeding into each phase.

This is very important with larger (6 kW and greater) solar inverter systems as if all the power was feeding down one phase it may well be too much load on the single phase and create an unbalance between the loading of the phases. For solar power systems with inverters of 5kW in size or smaller this isn’t generally an issue because 5 kW of power feeding down 1 phase is not usually a problem. I say not usually a problem as sometimes smaller solar power systems between 3 to 5 kW do require a 3 phase solar inverter.

When Would I Need a 3 – 5 kW 3 Phase Solar Inverter?

As mentioned above the main benefit of a 3 phase solar inverter is that it feeds power into your property over all 3 phases. There are situations where a single phase 3 – 5kW inverter will just not work; or more likely it will work fine in low light conditions but will come up with a fault in perfect conditions! There is nothing more annoying than having a solar power system producing nothing at all at a time when it should be producing lots of power! When this happens it is due to resistance in the main power cables on the property. Lets look at why this resistance causes a problem.

How A Grid Connect Inverter Feeds Power

A grid connect solar power inverter takes the DC solar power from your roof, converts it into AC power as efficiently as possible and then feeds it into your property’s switchboard. In simple terms the inverter “pushes” its power into the power cables on your property and the more power it has to push the more force required.

Consider a water pipe. If you only need a small amount of water to flow through the pipe then you don’t need to apply much pressure at all, but if you want to get a lot of water through that same pipe it needs to be forced in under pressure. It is the same with a solar inverter. If it needs to feed a lot of power into small cables or if the cables span a long distance it applies more pressure to feed the power in by raising the AC voltage. All grid connect inverters are constantly monitoring the AC voltage and if it goes too high they will automatically shut down, and this will be happening when the system should be working at it’s best if the cables are too small for the length the power needs to be pushed.

In this situation a 3 phase solar inverter will cut the amount of power being pushed into each phase by a third; this effectively means the 3 phase inverter doesn’t have to push anywhere near as hard as a single phase inverter of the same capacity; and if the inverter isn’t pushing as hard the voltage will not be raised to the point it causes the inverter to cut out. This really is only an issue for 3 – 5 kW systems when the solar power system is installed a long way from the street power lines and / or the AC power cables from the inverter back to the street power lines are too small.

If your solar power system is on a rural property at a distance from the street power lines we recommend a site inspection to ascertain whether your property will suit a single phase or 3 phase solar inverter as we can calculate the expected voltage rise and efficiency of a system at your property by inspecting your site.

In Conclusion..

A 3-5 kW 3 phase solar inverter is normally only required on rural properties where the solar power system is installed a long way from the street power lines. This is because the inverter could possibly have to raise the voltage above its preset limits to “push” the power it is generating back to the street. Whether this is required can be quickly ascertained through a site inspection by the solar power experts at Gold Coast Solar Power Solutions. Another question we are often asked is about how single phase solar works with maximising self consumption when you have 3 phase. For the answer please click on the following link: 3 phase power and solar – Do I need a 3 phase solar inverter?

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