Skip To The Main Content

Variable AC Power Sources

Superior Electric designs, manufacturers, and markets variable AC power sources using our wide range of POWERSTAT® and Volt- Pac® Variable Auto-Transformers. Our experts design special units and "value-add" assemblies to meet specific customer requirements with ease.


Our variable AC power supplies make it easy to build a stable AC power test bed for testing product reactions to simulated harmonics conducted on the AC power line. Superior Electric provides all the options and expertise to customize a variable AC power solution for your unique applications, specifically simulation of AC anomalies such as circuit breaker test sytems, watt-hour meter test systems, lighting ballast test systems and appliance tests and burn-in.

Variable AC Power Source

Variable AC Power Source Features

Electrical Parameters

  • Standard 120, 208, 240, 277, 380, 480, 575 and 600 VAC types
  • Additional autotransformers, multi-tapped transformers, and isolation transformers
  • Custom output boosts of 20%, 25%, and 30%
  • DELTA- DELTA, WYW- WYE, and DELTA- WYE connection configurations
  • An input circuit breaker to serve as an undervoltage trip release or shunt trip
  • Output contactor to serve as a REPO switch
  • Line, boost, and step- up connection options
  • Overload capacity, temperature, regulation
  • 50, 60, 400 Hz types

Load Ranges

  • Capacities to 1000 amps
  • Custom low- voltage/ high current
  • Custom high voltage/ low current


  • NEMA 1 with multi- knockout panels for ease of wiring
  • Heavy Duty Caster Kit options with locking swivel and push/pull handles
  • Fan assemblies

Control Options

  • Manual Handwheel
  • Synchronous Motor
  • Digital Step Motor
  • Single or Individual Phase Control
  • Extra Limit Switches for high/low positions
  • Full-Range Controllers (0-10V, 4-20mA, microprocessor)
  • Control Panel types for auto/manual and raise-lower switches

Environmental Options

  • Fan assemblies
  • Tropicalization

Monitoring Options

  • Analog Voltmeter(s)/ Ammeter(s)
  • Digital Voltmeters(s)/ Ammeter(s)
  • Digital Power Meter (Volts, Amps, Hz, PF, and more)
  • LEDs, Alarm Contacts

Variable AC Power Source Features

We Make It Easy To Build Custom Variable AC Power Sources

Specifying a variable transformer and matching components to build your test set can be complicated. Contact our experts to learn how we can build a customized assembly for your unique voltage test requirements.


Contact Our Experts Today:

What is a variable AC power supply?

A variable AC power source is a controlled, yet variable, voltage solution. Variable AC power sources are commonly used in conjunction with test equipment to simulate extreme variations of voltage condition. Event conditions such as sags, sustained low voltages, surges, over-voltages, sustained over-voltage conditions, and high/ low nominals beyond commercially available power sources could cause a device to malfunction.

What are the types of variable AC power supplies?

A variable AC power source comes in three types, including simple manual, motorized, and sophisticated interface with automatic control schemes. The environmental and monitoring parameters along with the voltage and load amperage requirements of the application will help determine the best type of variable AC power source.

How do you make an adjustable voltage power supply?

Variable AC power sources are engineered assemblies made up of standard or special variable transformers, zig-zag neutral generating transformers, and multi-tapped buck-boost or special ratio auto-transformers. Additionally, electrical components such as SUPERCON® specialty connectors, circuit breakers, contactors, bypass switches, emergency power-off devices and meters are commonly included in variable AC power source assemblies. Experts position and wire each all required components together to make an effective and cohesive assembly.