An electricity inverter converts direct current, or DC power, from batteries into alternating current, or AC. This is essential for operating appliances that require constant, steady voltage, such as household appliances, pumps and electric grinding wheels. Inverters may also be used to power generators, fans, massagers, computers, air conditioners and video recorders.
Battery-based inverters are often used in RVs, campers and boats to power appliances and tools when the grid is unavailable. They are also commonly found in solar power systems, where they connect to photovoltaic panels to provide power when the sun is shining. Smart inverters can help stabilize the electric power grid by detecting deviations in voltage and frequency and changing their power output to match, or “ride with,” small disturbances in the grid. If the disruptions last longer than expected or are too large, the inverters can disconnect from the grid and shut down.
The type of inverter you choose will depend on your power needs. For example, if you plan on running heavy-duty equipment, like air conditioners or motors, select an inverter with a peak surge rating greater than 1440 watts. Alternatively, if you are using the inverter as part of a grid-tied solar system, select an inverter with a UL listed grid-tied mode. This is a safety feature that ensures that the inverter can safely feed back into the utility power grid when connected.
There are several types of inverter circuit topologies that produce different power quality levels. A square wave, modified square wave and pure sine wave are common choices. The square wave has low power quality, while the pure sine wave provides a clean power signal similar to that of utility-supplied electricity.
The basic inverter topology uses semiconductor devices called power MOSFETs to switch on and off at high frequencies like 50 kHz to transform the DC voltage from the batteries into the higher frequency AC signal required by most appliances. The signal goes through step-up transformers to increase the voltage and then is filtered by capacitors to remove high-frequency components, leaving a modified sine wave.
To prevent the inverter from being overloaded by too much current, a fuse or circuit breaker must be installed inline with the positive cable from the inverter to the battery. If the inverter experiences a short circuit, the fast acting fuse or breaker will blow within milliseconds to protect the system from damage and fire hazards. The recommended fuse or circuit breaker size can be found in the owner’s manual of your inverter. It is important to use a properly sized fuse or circuit breaker in order to avoid overloading your batteries and cables. Too large a fuse could cause the cables to overheat, which is dangerous and can cause the inverter to shut down. The proper cable gauge is also critical to ensure a safe installation. Check the recommended wire gauge in your inverter’s owners manual to find the right one for your system.