Decisions, decisions. You’re reading this because you’ve done some extensive research into solar power, but there are a few more answers you need before proceeding with your venture. Before we can answer the question about 3-phase solar inverters, it makes sense to review the two main power delivery types upon which your power supply is based.
If you want to learn more, please visit our website 3 phase solar inverters.
From there, we can consider the type of solar power inverter to employ and whether you need a battery inverter charger. It all depends on your use case.
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Before You Get a
3-Phase Solar Inverter
: Check if You Have a Single-Phase vs. Three-Phase Power Supply
Deciding between a single-phase or three-phase power supply is one of the easiest and most basic determinations to make when installing a building’s electrical system. The main factor is the total electrical load the system is expected to draw.
Average residential homes and small businesses (think stores, three or four-room offices) need only a two-wire (one conducting, one neutral), single-phase power supply for running heating and air conditioners, plus various appliances and lights.
Many mid-sized businesses, large housing developments, and industrial units are better served with a four-wire (three conducting, one neutral), three-phase power supply. It can better accommodate higher loads, such as driving powerful electric motors and pumps.
Advantage of Three-Phase Power Over Single-Phase
Since a three-phase power supply can extract three times as much current from the electrical grid, it can transmit three times more power to the structure than a single-phase power supply. Another reason three-phase is better for industrial use is the consistency of power delivery. Single-phase is more susceptible to voltage rise and dips, whereas three-phase delivers power at a steady, constant rate.
Accordingly, most industrial buildings are three-phase, whereas small commercial units can make do with a less expensive and simpler single-phase system.
Want to See if Your Building Has Single or Three-Phase Power Supply?
Have a look at your switchboard, being careful not to touch anything. Count the poles on the levers labeled Main Switch. If there is one lever, you have a single phase. If there are three levers (usually labeled 1, 2, 3), you have a three-phase power supply.
Deciding Between a Single and
3-Phase Solar Inverter
Logically, you might assume that if you have a three-phase power supply, you would need a three-phase solar inverter for your solar panel system. However, even if you have 3-phase solar power, a single-phase inverter may be enough.
Single-phase solar inverters are simpler and cheaper than three-phase solar inverters. This simplicity makes them ideal for connection to a single-phase power supply, but you can also connect them to one phase of a three-phase system.
So, if the solar system installed in your building is three-phase, the inverter will only work on one-third of the system. The solar energy power from the other two phases could be sold back to the grid.
An issue with single-phase inverters when feeding power back into the grid is voltage rise. On a day with good solar power generation and low demand in your building, it’s possible that your solar panel system might send too much voltage into the grid.
If that’s the case, the inverter will likely trip to protect itself, shutting off entirely. A three-phase inverter will help alleviate that problem by spreading the load more evenly.
A single-phase solar inverter would not be appropriate for an off-grid 3-phase solar power system with a battery bank because the power from the other two phases would be wasted.
3-Phase Solar Inverter
A 3-phase solar system is designed to meet greater electrical demand; thus, using a 3-phase solar inverter makes sense when attached to a 3-phase electrical system.
In the case of an on-grid solar system, a 3-phase solar system design can send more power back into the grid. 3-phase inverters also reduce the risk of voltage rise by sending solar power to the grid via three cables instead of just one, thus spreading the load.
In addition to the increased power delivery potential, three-phase solar inverters are better at delivering power evenly to different areas of the structure. More power on tap generally equals more stable energy. Acting as inverter chargers, they can also deliver more consistent power to charge the solar battery bank.
Finally, 3-phase inverters are the most appropriate choice for off-grid 3-phase solar power systems. They allow the full potential of the solar system to be harnessed.
Making the Right Choice in Solar Inverters
As we’ve seen, there are many factors to consider when deciding between inverter types, brands, and capacities. Some examples of popular inverters are the Fronius Symo 3.0 and SMA Sunny Tripower. They are both good representatives of a three-phase battery inverter charger.
Smaller home solar systems are usually well served by a single-phase inverter. Still, larger 5KW solar systems and up are better served by a 3-phase solar inverter to take advantage of all the benefits discussed above.
Single or
3-Phase Solar Inverter
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for Your Property? We’ll Find the Right One
At Airis, we make installing a solar power system completely seamless. If you want to take a hands-off approach, our team can size the system appropriately for your needs. Alternatively, if you want to be fully involved in the decision-making process, we’ll be happy to educate you on the different aspects of your solar power system.
Book your free on-site consultation today to find out how large your solar power system can be, what type of inverter is best for your needs, and more.
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I love three-phase solar inverters.
If your home has a three-phase supply and you do not want or need micro-inverters then my recommendation is to use a three-phase solar inverter over a single-phase model.
A three-phase solar inverter takes DC electricity from solar panels, chops it up and sends it out as AC electricity shared across a three-phase supply.
They cost about $300 more than the equivalent single-phase solar inverter, but look the same:
Most homes in Australia have a single-phase electricity supply. This means that they have one live wire coming in from the grid.
A three-phase home has 3 live wires coming in from the grid.
This means three-phase homes can pull more power from the grid. Handy for particularly big loads such as a:
And of course a three-phase supply means you can send much more solar energy back into the grid compared to single-phase (three to six times as much depending on your local DNSP rules).
Carefully (don’t touch anything!) look in your switchboard. Count the ‘poles’ on your main switch or meter isolator. If you have single-phase you’ll only have one. Three-phase homes will have 3 like this:
If you have three-phase supply you can have either:
Any of these choices are valid. It will not affect how you are billed for exports or how much solar energy is self consumed.
But, I still recommend a three-phase solar inverter.
Spreading the inverter capacity across the three wires coming into your home means that you don’t have to push the solar energy as hard to get it out to the grid. You’ll be increasing the local grid voltage less than a single-phase install and you’ll have less throttling or tripping off due to over-voltage issues. That means more solar power production with our high-voltage plagued Australian grid.
Voltage rise related solar issues are one of the biggest problems we see with installed solar power systems. I go in to detail on the causes and solutions for voltage rise issues here.
So to reiterate for the blog post skimmers:
If you have a three-phase supply I recommend getting a three-phase solar inverter. Why? Because it drastically reduces the chance of having voltage rise issues.
But not everyone agrees with me on this.
There is one downside to using a three-phase inverter other than the extra cost (expect to pay $300 to $500 more compared to a single-phase inverter). Three-phase solar inverters do make it much more expensive to have ‘Apocalypse Proof Battery Backup™’.
My definition of regular battery backup is this: when the grid goes down your battery system powers some specially selected ‘essential circuits’. If the battery gets drained during the blackout, your home will black out too. In this configuration, the solar panels cannot charge your battery without the grid.
My definition of Apocalypse Proof Battery Backup : when the grid goes down your battery system powers some specially selected ‘essential circuits’. But if the sun is shining the solar panels help power your home and recharge the battery too. If you are careful with your consumption, you can carry on indefinitely charging the batteries with the sun by day and using the battery at night.
If you have a three-phase home with a single-phase solar inverter (or microinverters) then, with the right battery – such as a Powerwall 2 – Apocalypse Proof Backup is easy and can be done out of the box:
When the grid goes down in this configuration the battery system isolates the house from the grid (islands) and keeps 230V on the ‘black’ phase so the solar inverter does not shut down. The solar panels continue to send power to the house and battery. The solar inverter is throttled using frequency shifting if there is ever more solar power than the house and battery can handle.
But if you add a battery to a system with a three-phase solar inverter it is more complicated. If the grid goes down you need to keep 230V on all three-phases to stop the solar inverter shutting down. A battery with a single-phase battery inverter (such as a Powerwall 2) cannot do this. You will be able to have ‘regular’ backup – but once the batteries are drained you’ll have no power until the grid comes back.
The solution to this is expensive. You either need a three-phase battery inverter – and if you know of one please let me know in the comments – I’ve never seen one for sale. It would look like this:
Or you have 3 batteries and battery inverters – one on each phase. But again – I don’t know of any battery systems that can play nice with a separate three-phase solar inverter. The Powerwall 2 cannot work in this configuration. Yet.
Or of course you could swap your three-phase solar inverter out for a three-phase hybrid inverter and DC Couple your battery:
But all these options are very expensive. So if you are choosing between a three-phase solar inverter and a single-phase solar inverter/microinverters the question you have to ask your self is:
In my humble opinion it is better to have a system that operates well 99.9% of the time (when the grid is available) over one that operates really well 0.1% of the time (when the grid is down).
But perhaps your grid electricity goes down much more than that and getting through long outages is your priority. In that case you may want to install a single-phase solar inverter on your 3-phase supply. Just make sure that your installer checks your local grid voltage and voltage rise before you get solar installed. And hope that your local grid voltage stays low in the future.
You could also install a three-phase hybrid inverter instead of a three-phase solar inverter. But bear in mind that any future battery must be compatible with that inverter – often that is only 2 or 3 battery models and they may be obsolete by the time you decide to buy them.
So choose wisely three-phase dweller. And do the right thing based on your local grid voltage, your local grid reliability and above-all your zombie tolerance.
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