The AC Automatic Voltage Regulator

The automatic voltage regulator or AVR, as the name implies, is a device intended to regulate voltage automatically: that is to take a varying voltage level and turn it into a constant voltage level.

There is tremendous diversity in the size and type of devices that could qualify to be called an automatic voltage regulator. To get a sense of the degree of diversity among AVRs, consider an analogy about the term “spotlight” which can mean pixel-sized all solid state elements found in display devices to truck-mounted, power guzzlers to illuminate the night sky.

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The diversity of automatic voltage regulators in size and design is reflected in the tremendous variety of names for AVRs:
  • Auto-boost regulator
  • Constant voltage regulator
  • Constant voltage transformer
  • CVT
  • Double conversion electronic voltage regulator
  • Electromechanical voltage regulator
  • Electromechanical voltage stabilizer
  • Electronic tap switching voltage regulator
  • Electronic voltage regulator
  • EVR
  • Ferro
  • Ferroresonant transformer
  • Ferroresonant voltage regulator
  • LDC
  • Line voltage regulator
  • Line drop compensator
  • Magnetic induction voltage regulator
  • Magnetic induction voltage stabilizer
  • Mechanical tap changing regulator
  • Motor-driven variable autotransformer
  • Motorized variac
  • Motorized variable transformer
  • OLTC
  • On load tap changer
  • Servo voltage regulator
  • Servo voltage stabilizer
  • Step voltage regulator
  • Tap changer
  • Tap-switching voltage regulator
  • Variable autotransformer
In the sections describing the different types of voltage regulators, the common names for each type will be identified and used interchangeably along with generic names such as AVR and automatic voltage regulator. Also note that the descriptions, operational explanations and other commentary provided about the different types of AVRs is for informational purposes only and is intended to provide an overview of variations among a class of products generically called “automatic voltage regulators.”