Three phase surge suppressors protect electrical equipment from voltage transients on three phase alternating current (AC) power lines.

Understanding Three Phase Power

Three phase power systems are polyphase systems that use at least three "hot" conductors to deliver three different independent AC currents. Taking one current as a reference, the other two currents vary by one third and two thirds of a cycle, respectively; the currents may also be referred to as being separated by 120°. The diagram below shows a typical three phase AC signal.

Image credit: J JMesserly

Three phase power systems are advantageous in that they deliver a balanced load. The fluctuations of a single phase power system cause wide variations in voltage as well. Because of the offset nature of three phase power signals, these variations are minimized, increasing the system's efficiency. Other advantages of three phase power include:

• Reduced generator and motor vibrations due to a balanced load
• Minimizing or eliminated the neutral conductor due to a balanced load
• Ability to create and control a rotating magnetic field, simplifying electric motor design

Referring to the second of the above three points, three phase systems without a neutral conductor are known as "3-wire" systems, while those that include a neutral wire are known as "4-wire." The fourth neutral wire is often added when manufacturers believe that a risk of an unbalanced load exists.

The image below shows a typical three phase circuit with 120° separation.

Image credit: All About Circuits

In North America, three phase power is not typically used for residential applications except to power clothes dryers or electric ovens. Instead, it is typically used to power large motors and other heavy industrial equipment that requires large amounts of power.

Specifications

For more information about a three phase surge suppressor's technology, standards, and certification, please visit Engineering360's Surge Suppressors Selection Guide.

Form Factor

Surge suppressors may be manufactured as a number of different form factors or mounting types.

• Wall / backboard devices feature mounting holes and are bolted to a wall.
• Rack-mounted devices fit inside of a panel, which may be a standard 19" telecommunications rack.
• DIN rail products mount on a rail standardized by the Deutsches Institut für Normung, a German national standards body. Common rail widths include 15 mm, 35 mm, and 75 mm.
• Hard-wired suppressors mount directly on or within the device they protect.
• Plugin products plug into an existing system or power module.
• PCB surge suppressors are wired directly onto a printed circuit board (PCB).

Voltage

It is important to match a surge suppressor's intended voltage with the voltage of the applicable system. Common residential voltages include 120 V, 240 V, or 120/240 V. Commercial or light industrial systems may use higher voltages, such as 380 V, 480 V, 600 V, or 347/600 V.

Image credit:

ABB Electrification Products