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In direct current (DC) circuits, this product is equal to the real power, measured in watts. [3] The volt-ampere is dimensionally equivalent to the watt: in SI units, 1 V⋅A = 1 W. VA rating is most used for generators and transformers, and other power handling equipment, where loads may be reactive (inductive or capacitive).
A current transformer (CT) is a type of transformer that is used to reduce or multiply an alternating current (AC). It produces a current in its secondary which is proportional to the current in its primary. Current transformers, along with voltage or potential transformers, are instrument transformers. Instrument transformers scale the large ...
The equivalent power rating of the autotransformer is lower than the actual load power rating. It is calculated by: load VA × (|Vin – Vout|)/Vin. [2] For example, an auto transformer that adapts a 1000 VA load rated at 120 volts to a 240 volt supply has an equivalent rating of at least: 1,000 VA (240 V – 120 V) / 240 V = 500 VA.
A distribution transformer or service transformer provides a final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. [ 1 ] The invention of a practical, efficient transformer made AC power distribution feasible; a system using ...
Inrush current. Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform.
IEC 60227 Polyvinyl chloride insulated cables of rated voltages up to and including 450/750 V. IEC 60228 Conductors of insulated cables. IEC 60229 Electric cables – Tests on extruded over-sheaths with a special protective function. IEC 60230 Impulse tests on cables and their accessories.
All four plots use the passive sign convention. A current–voltage characteristic or I–V curve (current–voltage curve) is a relationship, typically represented as a chart or graph, between the electric current through a circuit, device, or material, and the corresponding voltage, or potential difference, across it.
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.