Inverters or Solar Inverters are used in PV systems for converting DC electricity in AC.
Now often in solar PV systems, low voltage DC is converted (that could be 12 V, 24, 48 V or 96 Volts) to much higher voltage AC current (around 220 Volts) that we can use in our electrical appliances. For stepping up the voltage, a transformer is present inside the inverter.
In a Low frequency inverter, a large transformer is present. The low frequency inverters are good at handling high impedance loads such as running a pump or compressor.
High frequency inverters on the other hand have a smaller inverter installed in them. Since 2010, a newer type of Inverter has penetrated the market and it is called a transformerless inverter.
In the chart shown below we can see that transformer-less inverters outperform both high and low frequency inverters.
In a transformer less inverter, the process of stepping up voltage is achieved by means of a computerised multi-step process. The electronic components to convert DC to high frequency AC, back to DC, and ultimately to standard-frequency AC.
A transformerless Inverter is lightweight, because of the absence of transformer. This allows installers the flexibility of rooftop installations without the need of reinforcement. The shipping costs are also low.
Their superior efficiency, allows them not only to give greater yield, but the internal architecture is such that it can cater for not one Dual MPPT inputs.
Transformerless are very common in Europe and have only lately made inroads in the US market. The reason is that all electrical systems in the US practically grounded electrical systems. In a traditional inverter, the galvanic isolation is provided by the internal transformer. Installers are just cautious because in a tranformerless inverter there is no electrical isolation between the AC and DC circuit. But transformerless inverters can be grounded by means of additional circuitry. It’s more a case of unfamiliarity than safety that installers in the US are apprehensive about this product.
Most modern inverter produced are transformerless simply because of superior efficiency.
They are also low cost. In the industry the “TL” abbreviation is normally used in the product name to identify an inverter being transformerless.
The are many “opensource” circuit diagrams available on the internet that can guide you how to make an inverter at home if you feel like making one.
So just to recap, Transformerless are more efficient, less costly, less heavy and can allow for dual MPPT option
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