Power 101: Power Supply Considerations for Harsh Environments

Power supplies for harsh industrial environments must stand up to electrical, environmental, and mechanical challenges. For example, to withstand potential voltage fluctuations and transients due to brownouts and power surges, rugged power supplies must have a wide input voltage range and excellent immunity to dips and over-voltage surges. Most power supplies operate off one of the standard voltages from 100 to 240 volts AC. However, in order to operate off the industrial 480 volt three-phase power, industrial power supplies should have a wide input voltage range and be rated for a nominal 277 volts AC.

Electromagnetic compatibility is also a serious concern for power supplies in order to mitigate electromagnetic interference, which may affect other equipment. Likewise, EMC immunity against power surges, dips, ESD, and electrically fast transients is vital to protect the power supply and meet industry safety requirements. Over-voltage categories range from the lowest Category 1 rating to the highest Category 4 rating, based on the location and expected transient voltages. For both reliability and safety, engineers should be familiar with these over-voltage categories, in order to choose the correct power supply for their application.

Ruggedized power supplies must start up efficiently at low temperatures, remain cool at hot temperatures, and deal with humid environments. In hot environments, effective thermal management, including convective or liquid cooling, are major considerations. To support high temperatures, rugged steel enclosures include ventilation holes to enhance convective cooling. Therefore, the internal components must be protected against moisture and dust by a conformal coating.