Chapter 2 – AC Power Distribution

This chapter provides recommendations for powering control systems from AC sources, including information on single-phase power, three-phase power, transformer isolation, distribution, power supply connections, and AC connections to workstations. Commercial AC power utilities normally provide power that meets the voltage and frequency requirements of the control system. To maintain good AC power quality, items such as power loss, intermittent noise, low voltage, transients, and surges on power lines must be designed around or otherwise controlled. Process application and process availability are critical factors for determining the amount of noise protection desired. Loads, such as AC drives and solid-state switching electronics, on AC power systems other than the control system cannot be ignored. These loads can induce electrical noise on nearby power systems. Most control systems use single-phase power in a voltage range of 85 to 264 Volts and a frequency range of 47 to 63 Hz. These ranges allow for AC input power from normal 120 VAC and 240 VAC sources.