AC motors and generators. Exercise 1.

 Переведите на русский язык следующие предложения:

  1.    A simple generator without a commutator produces AC current.
  2.   The current alternates as the armature rotates through the magnetic      field.
  3.    AC generation is best for power distribution.
  4.    There are 2 differences between AC and DC generators.
  5.    AC generators have 2 slip rings instead of a commutator.
  6.    AC field coils are energized by an external DC source.
  7.    Low-speed AC generators are built with as many as 100 poles.
  8.    The AC frequency depends on the number of poles and the speed of rotation.
  9.    100poles rotated at 1 revolution per second = 50 cycles.
  10.    2 poles rotated at 50 revolutions per second = 50 cycles.
  11.    Revolutions is normally quoted per minute so 1 per second =50 RPM
  12.    50 per second = 2500 RPM.
  13.    To reduce transforming higher voltages are generated which require    special generators.
  14.    The armature is not rotated to reduce sparks. The magnetic field is rotated.
  15.  Alternators therefore have a rotating magnet inside coils of conductor.
  16.   AC current alternates as follows:

   - Conductor at 90 degrees to pole = no current;

   - Conductor at 0 degrees to pole =maximum current;

   - Conductor at –90 degrees to pole = 0 current;

   - Conductor at 180 degrees to pole =Maximum negative current;

  1.    This is known as single-phase current.

18.   An armature with 2 coils at 90 degrees produces 2 phase current.

19.   An Armature with 3 coils at 120 degrees produces 3 phase current.

20.    3 Phase generation is the most common form of generation.

  1. Voltages as high as 13,200 are common in alternators.