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In the power systems analysis field of electrical engineering, a per-unit system is the expression of system quantities as fractions of a defined base unit quantity. . Calculations are simplified because quantities expressed as per-unit do not change when they are referred from one side of a transformer to t
A common prefixed derived unit is "kilovolt-ampere" (symbol kVA). The VA rating is limited by the maximum permissible current, and the watt rating by the power-handling capacity of the device. When a UPS powers equipment which presents a reactive load with a low power factor, neither limit may safely be exceeded. [5]
In electrical engineering, power conversion is the process of converting electric energy from one form to another. A power converter is an electrical device for converting electrical energy between alternating current (AC) and direct current (DC). It can also change the voltage or frequency of the current.
This is a list of the power supply systems that are, or have been, used for railway electrification. Note that the voltages are nominal and vary depending on load and distance from the substation. As of 2023 [update] many trams and trains use on-board solid-state electronics to convert these supplies to run three-phase AC traction motors.
In a so-called balanced power system, sometimes called "technical power", an isolation transformer with a center tap is used to create a separate supply with conductors at balanced voltages with respect to ground. The purpose of a balanced power system is to minimize the noise coupled into sensitive equipment from the power supply.
Stand-alone switched-mode power supply An adjustable switched-mode power supply for laboratory use. A switched-mode power supply (SMPS), also called switching-mode power supply, switch-mode power supply, switched power supply, or simply switcher, is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently.
Grid-tie inverters convert DC electrical power into AC power suitable for injecting into the electric utility company grid. The grid tie inverter (GTI) must match the phase of the grid and maintain the output voltage slightly higher than the grid voltage at any instant.
Buck–boost transformers can be used to power low voltage circuits including control, lighting circuits, or applications that require 12, 16, 24, 32 or 48 volts, consistent with the design's secondaries. The transformer is connected as an isolating transformer and the nameplate kVA rating is the transformer’s capacity. [2]