enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. Volt-ampere - Wikipedia

    en.wikipedia.org/wiki/Volt-ampere

    Some devices, including uninterruptible power supplies (UPSs), have ratings both for maximum volt-amperes and maximum watts. 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.

  3. Mathematics of three-phase electric power - Wikipedia

    en.wikipedia.org/wiki/Mathematics_of_three-phase...

    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. In electrical engineering, three-phase electric power systems have at least three conductors carrying alternating voltages that are offset in time by one-third of the period ...

  4. Power density - Wikipedia

    en.wikipedia.org/wiki/Power_density

    Power density, defined as the amount of power (the time rate of energy transfer) per unit volume, is a critical parameter used across a spectrum of scientific and engineering disciplines. This metric, typically denoted in watts per cubic meter (W/m 3 ), serves as a fundamental measure for evaluating the efficacy and capability of various ...

  5. Kilowatt-hour - Wikipedia

    en.wikipedia.org/wiki/Kilowatt-hour

    In the case of devices that output a different voltage than the battery, it is the battery voltage (typically 3.7 V for Li-ion) that must be used to calculate rather than the device output (for example, usually 5.0 V for USB portable chargers). This results in a 500 mA USB device running for about 3.7 hours on a 2,500 mAh battery, not five hours.

  6. Uninterruptible power supply - Wikipedia

    en.wikipedia.org/wiki/Uninterruptible_power_supply

    Most UPS below one kilovolt-ampere (1 kVA) are of the line-interactive or standby variety which are usually less expensive. For large power units, dynamic uninterruptible power supplies (DUPS) are sometimes used. A synchronous motor/alternator is connected on the mains via a choke. Energy is stored in a flywheel. When the mains power fails, an ...

  7. Power factor - Wikipedia

    en.wikipedia.org/wiki/Power_factor

    At low values of power factor, more apparent power needs to be transferred to get the same real power. To get 1 kW of real power at 0.2 power factor, 5 kVA of apparent power needs to be transferred (1 kW ÷ 0.2 = 5 kVA). This apparent power must be produced and transmitted to the load and is subject to losses in the production and transmission ...

  8. Per-unit system - Wikipedia

    en.wikipedia.org/wiki/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 t

  9. Three-phase electric power - Wikipedia

    en.wikipedia.org/wiki/Three-phase_electric_power

    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 four including an optional neutral return wire) and is the most common method used by electrical grids worldwide to transfer ...