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The objectives of this section are to:
Solid-state electronics have become integrated into all aspects of industrial power supplies, converters, inverters, and choppers. Industrial power supplies are used in applications where a variety of voltages is required, such as power for PLC processors and their analog modules and other specialty modules. Power supplies are also used in all types of digital displays and cathode ray tube (CRT) color displays. One will find a power supply in virtually every electrical device on the factory floor. Any equipment that has electronic circuits in it must have a dc supply voltage available. Since all power in the factory originates as ac voltage, converters must be used in the power supplies to convert ac power to dc power. These circuits called converters will be similar to the diode rectifier circuits you may have encountered in basic electronic courses. Larger industrial systems such as motor drives, welding equipment, and battery chargers will require larger three-phase rectifier circuits.
Some industrial applications such as ac variable-frequency motor drives and welders will have a section where ac voltage is converted to dc and another section where the dc voltage must be converted back to ac voltage. The circuit that changes dc voltage to ac voltage is called an inverter. The inverter circuit is needed to change the dc voltage back to ac voltage because the frequency of the incoming ac voltage is fixed at 60 Hz and the output section of the drive needs to be able to provide the frequency of the output voltage between 0-120 Hz.
Choppers are special inverter circuits that take the dc voltage and convert it to a variety of other dc voltages. This is a useful circuit in dc motor drives where the dc voltage must be manipulated to provide changes in current and voltage for changing motor speed and torque characteristics. Chopper circuits are also used in welding power supplies and dc power supplies for a variety of other solid-state devices. This section will help one understand how solid-state devices are used in industrial power supplies to provide the correct voltages and frequencies through converters, inverters, and choppers.