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Foundations of electrical technology
Catellani&Smith:

Foundations of electrical technology

[6] / Foundations of electrical technology
  • Voltage or supply drop

    Difference in potential detected at the two ends of a wire, in lighting design the important value is that of the wire carrying electricity from the transformer to the lamp. It determines the maximum length of the wire which must remain within set maximum limits or the lamp will lose luminous efficiency.

  • Electrical current

    This indicates the quantity of current passing through a section of wire in a given unit of time. It is measured in amperes, a fundamental International System unit of measure.

  • Alternating current

    Indicated also as AC (for Alternating Current), it is a current whose direction and polarity periodically change. The frequency with which this occurs is measured in Hertz.

  • Direct current

    Also indicated as DC (for Direct Current), its intensity and direction remain constant in time. It is widely used in electronics, for example in powering LEDs. In electricity distribution, for practical purposes, it is preferred over alternating current.

  • Constant current

    This current is generated in such manner as to keep the intensity steady in time. In most cases, the LED modules are interconnected in series and powered by direct, constant current.

  • Constant voltage

    This current is generated in such a manner as to keep the intensity steady in time. The voltage of the household network is transformed into low voltage (usually a value of 12V) through the transformers that keep it constant to enable the operation of low voltage light sources. For instance, various versions of the Mini Giulietta are powered in constant voltage at 24V DC or at 5V DC (USB version).

  • Electrical voltage

    Difference in electrical potential detected at the ends of a wire. It is measured in volts.

  • Line voltage

    This term refers to the voltage at which the electrical current is distributed nationally. The voltage can vary from one country to the next; generally, in Europe, the line voltage is 220/230V while it is 110V in the United States.

  • In-series connection

    Circuit in which the components are connected to one another so that the current fiows over a single path. In the case of two-pole components, the end of one component is connected only to the end of the next component. LEDs are almost always connected in series, Catellani & Smith applies particular countermeasures to ensure that the failure of one LED will not compromise lamp function.

  • Parallel connection

    Circuit in which the components have the same poles connected to a different wire. All positive poles are thus connected together and likewise all negative poles are so connected. A typical example are ceiling lamps that continue to function even if one of its many bulbs should fail.