Model SureVolt - Automatic Voltage Regulator

The UST SureVolt™ is an automatic voltage regulator that uses solid-state devices (SCRs) to select transformer taps to regulate output within the desired range. UST units use a patented design, resulting in reliability far superior to our competitors’.

UST’s SureVolt™ is more reliable because:

1. UST’s configuration does not require the SCRs to handle the full load current (as other voltage regulators do), but merely a fraction of the load current.
2. UST sizes SCRs to operate between 1⁄4 and 1/3 of their rated current capacity.
3. UST’s patented technology does not require the unit to wait for a zero crossing of the current to initiate a tap change. When competitive units miscalculate the zero crossing, damage to SCRs or the transformer can occur. UST eliminates this potential problem by incorporating the ability to initiate tap changes at any time in the cycle. This also makes the UST SureVolt correct voltage faster than units that wait for a zero crossing.
4. UST incorporates an additional level of protection—a circuit breaker in the SCR path to protect the SCRs in case of over-current conditions (e.g., short circuit load) or other malfunctions.

Overload Capacity

The SureVolt uses a non-full-power semiconductor design to provide an overload capacity of 1000% for 1 second rather than 1000% or 1 cycle like other electronic power conditioners. This makes the SureVolt compatible with all load types and load power factors. The SureVolt delivers a minimum 1000% fault-clearing capability to permit circuit protective devices to operate properly. High overload capacity also means that the SureVolt does not need to be sized for the peak load current.

Current Interruption Eliminated

The SureVolt’s unique design eliminates the load current interruption seen in some power conditioners during switching. These interruptions to the current flow can create voltage spikes when switching, affecting sensitive loads and causing premature component failure.

Natural Convection Cooling

Cooling fans are a maintenance problem, and dirty fans can result in power conditioner failure. With 100% natural convection cooling, the SureVolt requires no fans or other moving parts. Other enclosure designs are available and can be quoted specific to customer requirements.

Fast Correction

The SureVolt provides fast voltage correction to keep sensitive equipment up and running. Programmable logic controllers (PLCs), variable frequency drives (VFDs) and instrumentation all benefit from the SureVolt’s short correction time (typically 1 cycle).

Electronic Failsafe Bypass

UST provides auxiliary circuit breakers in the SCR paths of the automatic voltage regulator design. When the current limit is exceeded or manually tripped, the SCRs are reset to the nominal path (no boost, no buck), and the unit is placed into non-regulation mode, where output voltage is similar to input voltage. When this circuit breaker is opened either manually or automatically, there is NO interruption to the load. The unit can be operated in this mode until it is appropriate to shut down the loads and take the unit off-line for maintenance. Most customers do not require a separate mechanical bypass. When in automatic internal bypass mode, some internal electrical components (e.g. the transformer and some SCRs) remain energized. In these cases, it is necessary to wait until the load can be removed and the unit can be completely de-energized before attempting maintenance.

The standard location of the auxiliary circuit breakers is inside the enclosure. UST users are in favor of this arrangement so access is limited to the appropriate personnel. UST can arrange to have the auxiliary breaker accessible from the outside if it is necessary to manually force the unit into internal bypass from an external switch.

If the EVR is functioning properly, however, a user should have no reason to initiate bypass mode, since the unit has no scheduled maintenance other than an annual cleaning.

All Digital Controls

All digital controls and operation permit the SureVolt to provide the highest levels of performance and accuracy in operation as well as a broad degree of customization for applications.

Simple Operation

The SureVolt uses microprocessor-controlled tap-switching technology with an isolated, shielded transformer and a unique control design that makes the SureVolt the industry’s leading automatic voltage regulator. The SureVolt conditions power with no operator or programming required. The standard LCD display provides information on the status and then-current operation of the unit while alarm contacts permit remote monitoring.

Easy Installation and Maintenance

SureVolt installation is as simple as setting it in place and installing the wiring in and out. The unit arrives completely assembled and requires no programming, testing, measuring, setting of switches or internal wiring. Maintenance is just as easy. With no moving parts, wear parts or fans, the SureVolt requires no regularly scheduled maintenance.