A motor–generator is a device for converting electrical power to another form. Motor–generator sets are used to convert frequency, voltage, or phase of power. They may also be used to isolate electrical loads from the electrical power supply line. Large motor–generators were widely used to convert industrial amounts of power while smaller motor–generators were used to convert battery power to higher DC voltages.
Aircraft radio modulator unit from the Second World War, showing a dynamotor (the black cylinder) which converts the aircraft's 24–28 V DC to 500 V DC for the transmitter. Dübendorf Museum of Military Aviation
An MG set used to provide a variable three phase AC voltage for an Electron Beam Welding Machine high voltage power supply.
A power inverter, inverter, or invertor is a power electronic device or circuitry that changes direct current (DC) to alternating current (AC). The resulting AC frequency obtained depends on the particular device employed. Inverters do the opposite of rectifiers which were originally large electromechanical devices converting AC to DC.
An inverter on a free-standing solar plant
Overview of solar-plant inverters
Inverter designed to provide 115 V AC from the 12 V DC source provided in an automobile. The unit shown provides up to 1.2 amperes of alternating current, or enough to power two 60 W light bulbs.
Internal view of a solar inverter. Note the many large capacitors (blue cylinders), used to store energy briefly and improve the output waveform.