# Common Electrical Terminology

Jessica Ciesla
August 20, 2019

Data center managers are on a constant road of innovation. As they implement new solutions, and respond to increasing demands for power, they must consistently consider a wide range of electrical factors. Whether you are exploring the benefits of high-power rack PDUs with sensors, or just beginning to delve into best practice approaches to reduce the carbon footprint of data centers, the following electrical term definitions can help you to better understand the intricacies of rack PDUs.

Common Electrical Terminology Involved With Rack PDUs

Active power (Watt): The active power refers to the watts that are being drawn by an IT device. Understanding the heat load of IT equipment is vital to proper load balancing.

Apparent power (VA): The product of the voltage applied to the IT device times the current drawn by the equipment. The VA is always equal to or larger than the active power. It is calculated by combining the reactive power and true power. The assigned VA rating is used for sizing wiring and circuit breakers.

Current (Amp): The rate of flow of electrons, ions, or holes in a conductor or medium between two points. The difference in potential is measured in amperes (amps), which are the ratio of the voltage to the resistance.

Ground: The ground is a conducting body that is attached from the object and connected (i.e. grounded) to the earth. It is used to safely direct stray currents into the ground.

Line: The line is an electrical conductor. For example, a single-phase system will typically have one line, while a three-phase system has three lines.

Neutral: The neutral is the electrical conductor that creates a return path for the voltage supplied by a line. However, it is important to note that the neutral itself is not a source of voltage.

Voltage (Volt): A volt is an electromotive force. It refers to the difference in electrical potential, by measuring the current times X the resistance.

4-wire and 5-wire systems: A 4-wire rack PDU consists of one ground wire and three lines. A 5-wire system is the same as the 4-wire system but with the addition of a neutral wire.

Three-phase Delta “∆“: This configuration gets the name Delta because a schematic drawing of it has three transformers forming a triangle or the Greek letter Delta. The three lines connect to the three “corners” of the triangle.

Three-phase Wye “Y“: This configuration gets the name Wye because a schematic drawing of it has three transformers meeting in the center forming the letter “Y”. The three lines connect to the three “branches” of the “Y” and the neutral connects to the center.

Discover The True Power Of The Right Electrical Configurations

In conclusion, one thing is certain, the right electrical configurations are vital to the success of your data center.  Discover the best in class solutions to power management, load distribution, security, and data center management with the help of the Raritan team. Contact Raritan to learn more.