Transcript Inverters
Inverters Alex Stanton Henry Schober III Benjamin Garber Rance What is an Inverter? An inverter is an electrical circuit capable of turning DC power into AC power, while at the same time regulating the voltage, current, and frequency of the signal Why do I need an inverter? Most solar panels provide 12V DC power Household devices use 120V AC power Necessary for a grid tie in system What kind of inverter do I want? Inverters come in all different shapes and sizes, for all different purposes Inverters vary in output from 50 – 5,000 W Several different methods of changing DC power to AC power Some inverters put out electricity of higher ‘quality’ than others. What does that mean? Electrical wave forms Graphs of voltage as a function of time Power that comes from a PV panel or battery is generally 12V DC Power Different types of inverters give outputs with different wave forms 12V DC Power Square Wave Modified Sine Wave True Sine Wave Different types of inverter output Square wave inverters are basically obsolete Modified sine wave output will power almost everything in your house. However, things like power drills, or battery chargers may not work True sine wave output is exactly the same as the power provided by a utility company, and is necessary for a grid intertie system Methods of inversion Rotary inverters use a DC motor to turn an AC Power generator, the provide a true sine wave output, but are inefficient, and have a low surge capacity rating Electrical inverters use a combination of ‘chopping’ circuits and transformers to change DC power into AC. They are much more widely used and are far more efficient and practical. Less expensive electrical inverters produce a modified sine wave, while more expensive models give a true sine wave. How do they work? There are 2 types of electrical inverters, the first takes low voltage high current power from a PV panel or battery and sends it through a ‘chopping’ circuit which changes it to low voltage high current AC power at 60Hz. The power then goes through a series of large transformers which output 120V AC power at 60Hz How do they work? The second type of electrical inverter is more complex. Two chopping circuits are employed to make it possible for a much smaller and lighter transformer to be used. The DC power is converted to very high frequency AC power which is easier to transform into high voltage low current power. The power is then rectified back into DC power and sent through a second chopping circuit to turn it into 60Hz 120V AC. How are Inverters rated? Continuous output rating: The maximum wattage that the inverter can support long term, includes all everyday appliances, lights and anything else that consumes power. Surge capacity rating: The maximum wattage that cam be supported at any given time. Important when starting devices like refrigerators or water pumps which require more wattage to start then to run. Applications of Inverters Inverters are used for many practical purposes Small inverters can plug into your car cigarette lighter Large inverters can be used in a solar or wind powered home