The rectifier sections are used in all types of industrial
applications. Virtually every piece of industrial equipment that has electronic
circuitry must have a means of converting ac voltage to dc voltage. These
systems use the rectifier circuits discussed earlier to provide the dc
power. The rectifier circuits will include capacitors and inductors for
filtering, and the combined circuit will be called a power supply. Industrial
power supplies will be slightly different from the ones used in consumer
products such as radios, televisions, and other electronic components
in that their supply will be single-phase and three-phase high voltage.
This means that the voltage level will normally be 208 or 480 volts.
It will be easier to understand the operation of these types of power
supplies if one examines several specific applications. The next sections
will explain the operation of the power supply circuit in two common industrial
applications: the ac variable-frequency motor drive and a welding system.
This section will also explain the operation of an uninterruptible power
supply (UPS) that provides backup voltage to computers and PLCs in case
of a power outage.