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Zener diode

Zener diode

  • The operation of a Zener diode is similar to a common diode in that the Zener only permits current flow in one direction. This is true until the voltage applied to the Zener reaches a certain level.
  •  At that predetermined voltage level, the Zener then permits current flow with either polarity. This is known as the breakdown or Zener voltage.
  • As an ACU monitors alternator output, the Zener diode is connected to system voltage. When the alternator output reaches the specific Zener voltage, the diode controls a transistor in the circuit, which in turn controls the alternator field current.
  •  This is a simplified explanation of the complete circuitry of an ACU. it is easy to see how the Zener diode and transistor circuit are used in place of an electromechanical relay in a vibrating-type regulator.
  •  The use of solid-state components creates a more accurate regulator that requires very little maintenance. The solid-state ACU is, therefore, the control unit of choice for modern aircraft with DC alternators.

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