The AC Automatic Voltage Regulator

The automatic voltage regulator (AVR) is a device designed to regulate voltage automatically – that is, to take a fluctuating voltage level and turn it into a constant voltage level. There are many types of automatic voltage regulators.

SureVolt Face On 400 v2


The UST Sure-Volt™ voltage regulator/power conditioner provides the broadest range of protection available to guard valuable equipment and maximize your bottom line with industry-leading overload capacity for compatibility with all loads types. Other features include built-in surge suppression for surges and spikes, line isolation to minimize transient events and noise, transformer shielding to reduce line noise and deliver clean power, and much more.


MiniEVR_siloThe UST Mini-EVR™ voltage regulator/power conditioner is UST’s answer to the ferro. Based on the same technology found in UST’s Sure-Volt™ power conditioner, the Mini-EVR™ provides the same fast response time, high overload capacity, industrial-grade durability and easy application as its big brother. The Mini-EVR™ is designed for small, single-phase loads and is packaged in a smaller, less expensive configuration. Most importantly, the Mini-EVR™ offers superior protection from power quality problems without busting your bottom line with high energy costs associated with traditional power conditioners. To calculate your savings, use our online calculator.

Automatic voltage regulators not only vary in size and design, but also in name and description. Common names for AVRs include:
  • 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, common names for each type will be identified and used interchangeably along with generic names, such as AVR and automatic voltage regulator. Please 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.”