The UST MiniEVR™ is an industrial-grade automatic voltage regulator featuring a non-full-power semiconductor design.

The MiniEVR continuously monitors output voltage and quickly switches transformer taps when voltage falls outside regulation range. The MiniEVR™ automatic voltage regulator continuously conditions power with no operator or programming required. In the event of a malfunction, the automatic bypass actuates to isolate power electronics and controls while maintaining power to the load.

Industrial-grade means our MiniEVR is compatible with all load types and load-power factors and provides a minimum 1,000% fault-clearing capability. Unlike computer-grade products, the MiniEVR is designed for frequent high-inrush current and low-power factor loads without the need to oversize the product or sacrifice reliability.

MiniEVR Features

  • Highest overload capacity available for compatibility with all load types
  • Highest fault-clearing capacity available for reliable operation of protective devices
  • 99% efficiency for all but the lowest end of the load range
  • Continuous load current – no load current interruption on tap switching
  • Quickly corrects under/over voltage, sags, and swells
  • Automatic failsafe electronic bypass eliminates load current interruption in the event of a malfunction
  • Zero moving parts and fan-free design for increased reliability and no scheduled maintenance
  • Surge suppression and input circuit breaker are standard
  • Natural convection cooling

MiniEVR installation is simple. The unit arrives completely assembled and requires no programming, testing, measuring, setting of switches, or internal wiring. It installs much like a dry-type transformer: simply place the unit and make the input and output wiring connections.


Power Rating/Size (kVA) [1Ø only)

5, 7.5, 10 (for larger single-phase units, see UST SureVolt™ power conditioner)


60Hz: 120, 208, 240, 480

50Hz: 110, 120, 220, 380, 400

Non-standard voltages available

Regulation/Operating Characteristics


Nominal input voltage +10%/-22%; Nominal output voltage ±3 (other options available)

Regulation Variation

None – regulation constant for 0 to 100% load and any load power factor

Overload/Inrush Capability

6000% -1 cycle, 1000% - 1 second, 500% - 5 seconds, 200% - 1 min.; 1000% fault clearing

Load Power Factor

No limitations, compatible with all load types

Tap Switching

No load current interruption or waveform distortion on switching at any load or power factor

Zero Crossing Sensitivity

None: tap switching not dependent upon determining load current zero crossing

Harmonic Distortion

No distortion added at any load or power factor

Response Time

1 cycle typical regardless of load or load power factor


99% typical

Operating Frequency

±3% of nominal frequency

Protection / Bypass

Surge Suppression

Included, complies with ANSI/IEEE C62.41, UL 1449

Failsafe Electronic Bypass

Auto-actuation on high temperature, over-current, component failure with no loss of load



Microprocessor-controlled tap switching auto-transformer design

Switching Semiconductors

Non-full power semiconductors – individual SCRs are not required to carry full unit current


No controls or programming required; no user-adjustable controls


Natural convection; no cooling fans used


Dry-type auto-transformer, copper wound


Wall-mounted NEMA-1, ANSI 61 grey, other enclosure types and colors available


Contacts for remote indication of unit and surge suppression status are included

Audible sound level

Less than 65 dB @ 1 meter

Environmental Requirements

Temperature - Humidity

Ambient 32° to 104°F (0 to 40°C) – Relative humidity 0-95% non-condensing

Operating Altitude

0 to 3,300 ft (1000m)