What is a square wave inverter?

Answer 1

Inverters don't really put out nice, beautiful sine waves like you get out of an AC wall socket. Instead they chop DC current to APPROXIMATE the total current flow that a sine wave would carry at any instant in time.

A "regular" inverter is like one you plug into a car's cigar lighter plug to run a small TV, or even the inverter in the Prius.

The Prius inverter "chops" 500V DC to run the motors, providing "fake" AC.

The chopper is either on or off. 500V or zero V.

What a multi-level inverter does is have several voltage levels, 0, 250, or 500. So it can better approximate a sine wave than strictly an on/off, single level inverter.

The more levels an inverter has, the more efficient it can be, less EMI/RFI generation, and so on. But it's also a LOT harder to build, more expensive, harder to control in software.

Look for multi-level inverters to appear in electric vehicles in the next 5 years.

Answer 2

Square wave inverters are just switching not analog power converters. Sine wave ones would have better conversion values. The switchers square wave would be absorbed by your pole transformer. They can cause problems with household Electronics.

Answer 3

A power inverter with square wave output is easier to make and more efficient than a power inverter with sine wave output, but many loads must have sine wave output to function properly (e.g. motors).

Answer 4

An inverter consists of circuits which will take a DC supply ( like from a battery ) and convert it into an AC supply ( as in home power outlet ) .

It is to be noted that DC supply Voltage can be reduced ( may be inefficiently ) using simple devices , but cannot be increased easily as with an AC supply, where it is possible to obtain any required ( increased or decreased ) voltage using an appropriate transformer.

The basic reason being a transformer requires a constantly varying voltage to operate ( ideally a sinusoidal waveform ), whereas the DC supply provides a only a constant voltage level.

The simplest way to overcome this problem with DC is to have some means of continously interrupting the DC supply to a transformer in an appropriate manner such that the transformer will operate at a roughly varying supply voltage.

The easiest method being to switch the DC supply to the transformer, On & Off at carefully timed intervals. The interruptions in such cases will cause the transformer to be connected at either full DC voltage or zero voltage, but serving the purpose of transformer to operate. If a graph is plotted for the voltage against time, the supply output using such method looks like a train of squares or rectangular voltages. Hence the name Square wave inverter.

In the pre solid state electronics era, electromagnetic coils as in an electric bell , fitted with vibrating electrical contacts were used as the switching device and increase the voltage from batteries to power the then popular Thermionic Valves / Tubes which required high voltages to operate.

Now solid state devices like transistors , Mosfets , Thyristors , etc do the same switching function without any moving parts.

Since the ideal waveform for a transformer to work is not a Square wave , circuit jugglery is used to get a more realistic approximation of sine wave , in which case the inverter then is termed quasi sine wave. Such inverters are suitable for lighting & computer UPS systems where the supply waveform is not critical.

More sohisticated circuits can give good sine wave outputs, but being more expensive and required mainly for electrical motor type loads , where the changes in waveform can create unacceptable heating losses.