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Per-unit system. 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 the other.
Mathematics of three-phase electric power. One voltage cycle of a three-phase system, labeled 0 to 360° (2π radians) along the time axis. The plotted line represents the variation of instantaneous voltage (or current) with respect to time. This cycle repeats with a frequency that depends on the power system.
1 kg⋅m 2 ⋅s −3. The volt-ampere ( SI symbol: VA, [ 1] sometimes V⋅A or V A) is the unit of measurement for apparent power in an electrical circuit. It is the product of the root mean square voltage (in volts) and the root mean square current (in amperes ). [ 2] Volt-amperes are usually used for analyzing alternating current (AC) circuits.
Three-phase transformer with four-wire output for 208Y/120 volt service: one wire for neutral, others for A, B and C phases. Three-phase electric power (abbreviated 3ϕ[ 1]) is a common type of alternating current (AC) used in electricity generation, transmission, and distribution. [ 2] It is a type of polyphase system employing three wires (or ...
A tower type UPS with one IEC 60320 C14 input and three C13 outlets. A large data-center-scale UPS being installed by electricians. An uninterruptible power supply ( UPS) or uninterruptible power source is a type of continual power system that provides automated backup electric power to a load when the input power source or mains power fails.
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]
Motor velocity constant, back EMF constant. is the motor velocity, or motor speed, [2] constant (not to be confused with kV, the symbol for kilovolt ), measured in revolutions per minute (RPM) per volt or radians per volt second, rad/V·s: [3] The rating of a brushless motor is the ratio of the motor's unloaded rotational speed (measured in RPM ...
A split-phase or single-phase three-wire system is a type of single-phase electric power distribution. It is the alternating current (AC) equivalent of the original Edison Machine Works three-wire direct-current system. Its primary advantage is that, for a given capacity of a distribution system, it saves conductor material over a single-ended ...