Inverters

What is an Inverter?

A solar inverter converts [DC to AC].

What is called a rectifier you might plug into your car to run an AC appliance off of your DC battery.

Inverters are used to convert direct current (DC) into alternating current (AC) as needed – 120 volt AC powered homes. They also convert DC power from a battery banks to AC power.

Many Inverters now have an automatic shut off switch when there is no AC signal, so in a power outage your solar panels maybe able to work but your inverter wont put out. This is so when grid workers come and fix the outage they are not shocked by solar panels pumping electricity into the system. Certain override features can help you divert your solar panel power into your house, but be weary of this when purchasing an inverter and designing your system.

 

Sizing an inverter:

Inverters are classified as either battery-based or utility-interactive types.   You need to take note of power source, power ratings, input and output voltages, waveform, power quality, and power conversion efficiency. Many Inverters have a max input voltage of 600Volts.

Most inverters have high efficiency ratings of 95%, which can cause some voltage loss and derating.

 

Inverter Sizing

◦ Example– Suppose that you have available an inverter:

▪ Brand: X
▪ Model: ABC
▪ DC (STC) Continuous Power Rating = 2500 W
▪ DC Input voltage range = 150-450 VDC
▪ CEC Efficiency = 93.5 %

◦ (38 PV modules) x (200W STC) = 7,600 Maximum Watts Inverter(s) must pass
◦ 7600W ÷ 2500 watt rating = 3.04  3 inverters
◦ 38 PV modules ÷ 3 Inverters = 12.67 PV modules per inverter  12-13 modules per
inverter*

◦ *most inverters have a string sizing program on their website to calculate how many
modules in series are needed (This might require knowing your record high and low
temperatures for the installation site).

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