Three Phase Surge Suppressors Information

Three phase surge suppressors protect equipment from transient overvoltage’s present on AC three phase power lines. They carry specifications for maximum surge current, AC energy absorption, maximum AC power, and operating temperature. Maximum surge current is the maximum allowed current for a single impulse waveform with a continuous voltage applied. AC energy absorption measures a device’s ability to absorb heat energy created by transient surges. Three phase surge suppressors also differ in terms of technology, mounting style, wires and voltage, and standards and features. 

There are five basic technologies for three phase surge suppressors: metal oxide varistor (MOV), silicon avalanche diode, silicon thyristor diode, gas tube, and hybrid. MOVs have high-energy capabilities, good reliability, and consistent performance. Silicon avalanche diodes are used most often in data-line protectors and on circuit boards as static protectors. Silicon thyristor diodes are used mainly to protect telecom systems. Gas tubes have higher energy capabilities than either MOVs or diodes. Hybrid three phase surge suppressors incorporate features from other available technologies. 

Three phase surge suppressors differ in terms of mounting styles, number of wires, and voltages. Mounting styles include wall, panel or backboard mount; DIN rail; rack mount; hard-wired or device mounted; in-line or integrally attached; plug-in module; and printed circuit board (PCB) mounted. In addition to ground, three phase surge suppressors may have 2, 3 or 4 wires. The voltage specification for three phase surge suppressors lists the AC voltages for which devices are rates. Choices include 120, 208, 220, 240, 277, 346, 380, 480, 600, 120/240, 120/208, 220/380, 240/480, 277/480, and 347/600. 

There are numerous standards, approvals, and certifications for three phase surge suppressors. Ratings from Underwriters Laboratories (UL) include UL 1449, Second Edition; UL 497A, UL 1459, and UL 452. Products that bear the UL Mark, the CE Mark, or the CSA Mark are also available. CE marking indicates that a product complies with the essential requirements of relevant European Union (EU) directives that uphold national standards for health, safety, and environmental protection. Three phase surge suppressors that bear a CSA Mark have been tested by the Canadian Standards Association (CSA). 

Three phase surge suppressors may provide optional features. These include AC adapter spacing, audible alarms, complete pin protection, continuously live outputs, graphical displays, grounding wires, and integral disconnects. Hospital grade products must pass additional safety tests that measure leakage current. Some three phase surge suppressors are housed within NEMA enclosures. These enclosures are rated by the National Electrical Manufacturers Association (NEMA) and designed for hazardous or non-hazardous locations and indoor or outdoor use.

• Navigating the UL Safety Requirements for Surge Protection (,pdf)
  select a Mersen STT24803PYG. This is rated 277/480. volts supplied by a three-phase wye solidly grounded neutral source with not over. 200kA short-circuit current. This is UL listed for a fully compliant field installation. An OEM could select either the listed Mersen STT24803PYG as above, or the. Mersen...
• UL 1449 Rated Surge Protection
  suppression devices be marked with the surge let-through voltage for a specific UL test. By assigning a UL voltage rating for a particular mode (i.e. N-G), it can be inferred that this mode is protected against surges. For the three-wire, single-phase branch circuit commonly used in the U.S. and Canada...
• Surge Protection Excerpts from IEEE Standard 1100-2005. The Emerald Book: IEEE Recommended Practice for Powering and Grounding Electronic Equipment (.pdf)
  of EMI: "Depending on the severity of the surge and the susceptibility of the. equipment, three types of occurrences are possible... : data disruption, hardware stress, and. hardware destruction.". 4.4.5.1 Type I, signal-data disruption: "Signal-carrying circuits are susceptible to surge interference...