1.1 Summary

The function of the Automatic Voltage Regulator (AVR) is to maintain constant voltage and power line conditioning to the equipment load under a wide variety of conditions, even when the utility input voltage, frequency or system load vary widely. The AVR shall consist of an all copper, multiple tapped, triple shielded isolation transformer and contain independently controlled inverse parallel electronic switches for each of the 7 taps per phase to provide tight voltage regulation. The phase current shall be monitored for zero current recognition to initiate any required tap change. Linear devices shall be used for line synchronization to prevent phase shift errors normally associated with simple CT zero current crossing acquisition. The system shall be microprocessor controlled.

1.2 Quality Assurance

1.2.1 The manufacturer of the AVR shall be ISO9001 Certified for a period of no less than 3 years.

1.2.2 Qualification Data: For firms and persons specified in “Quality Assurance” Article.

Field Test Reports: The manufacturer’s technician shall submit a field test report within fourteen (14) calendar days following the completion of the site visit.

Product Test Reports: Certified copies of the manufacturer’s design and routine factory tests required by referenced standards.

Maintenance Data: As recommended by the manufacturer. Copy of maintenance manuals shall be provided. See Submittal Section.

1.2.3 Quality Assurance:

Provide Voltage Regulator as specified in this Section that is designed and built to comply with the following standards.

Standards & Agency Qualifications:

NFPA-70: Comply with NFPA 70; NEC article 250-5d (specifying a separately derived power source).

IEEE C2: Comply with IEEE C2.

IEEE C57.12.91: Comply with IEEE C57.12.91 Test Code for Dry Type Distribution and Power Transformers (ANSI).

IEEE C62.41: Recommended Practice on Surge Voltages in Low Voltage AC Power Circuits (ANSI).

NEMA 250-91: Enclosure of Electrical Equipment.

Underwriters Laboratory: UL 1012; Comply with 1449-85.


2.1 The AVR shall be of a solid state electronic tap switching design that shall comply with UL1012 for the intended application. Output impedance shall be 3.0 to 5.0 percent, depending on KVA rating. The AVR shall be manufactured such that it will maintain electrical properties, even under severe overload, under/over voltage and under/over frequency conditions. Input correction range shall be -30% to +20% of nominal input voltage. The system design shall be capable of operating at an input frequency range of -15% to +10% of nominal, without clearing protective devices or causing component failure within the AVR. When generator or utility power is restored, the AVR shall automatically restart. Upon turn on or restart, the output of the AVR shall not exceed the specified output regulation limits.

If the input voltage or frequency exceeds programmable minimum or maximum set points for a programmable time period (factory set for 10 seconds), the AVR shall electronically shut off. When electrical parameters are back within acceptable limits for a programmable time period (factory set for 60 seconds), the AVR shall automatically restart to provide conditioned power to the load. If the input parameters are within acceptable limits, but the output voltage is outside of acceptable programmed limits, the AVR shall electronically shut off and require a manual restart.

The AVR shall be capable of operating at 100% rated load capacity continuously, 200% rated load for 10 seconds, 500% rated load for 1 second and 1000% rated load for 1 cycle. Operating efficiency shall be a minimum of 96%, typical at full load. Transverse-mode noise attenuation shall be 3dB down at 1000Hz and 40dB down per decade to below 50dB with a resistive load. Common-mode noise attenuation shall be 140dB or greater.

Transformer winding shall be continuous copper with electrostatic tripled shielding and K-13 rated for the purpose of handling harmonic currents.

2.2 Response Time: The AVR shall respond to any line voltage variation in 1/2 cycle while operating linear or non-linear loads, with a load power factor of 0.60 of unity. Peak detection of the voltage sine wave shall not be permitted to avoid inaccurate tap switching due to input voltage distortion.

2.3 Line Voltage Regulation and Correction Time: Output regulation shall be +5%, -6%, given an input voltage variation of -30% to +30% for nominal, when within +/-5% of the nominal frequency. The AVR output voltage shall be corrected to within +5%, -6% or less within 1 cycle per tap for an under voltage condition. For an over voltage condition, the output shall correct within 1 cycle directly to the appropriate tap without stair-casing intermediate taps. Typical correction time shall be 1 to 2 cycles.

Load Regulation: No load to full load regulation shall be 3% typical under linear loading.

Note: The AVR shall be adjusted so that the combination of line voltage regulation and linear load regulation results in a maximum output voltage variation of +7% to -8% from nominal, when within +/-5% of the nominal frequency.

2.4 Operating Frequency: The AVR shall be capable of operating at +10% to -15% of the nominal frequency, 50Hz or 60Hz, with programmable high and low limits to alarm and electronically shut down the AVR. Limits shall be set to +/-2Hz from nominal and electronic shutdown shall occur if limits are exceeded for 10 seconds. Once back within limits for a programmable time period of 60 seconds, the AVR shall automatically restart.

2.5 Site Specific Data: The AVR shall be rated at ___kVA.

The input of the AVR shall be ___VAC, 3 phase, __ wire, Delta configured plus ground, __Hertz (nominal).

The output of the AVR shall be ___VAC, 3 phase, __ wire, WYE configured plus ground, __Hertz (nominal).

2.6 Access Requirements: The AVR shall have removable panels on the front, rear and sides as required for ease of maintenance and/or repair. Only one side of the unit shall require access for the replacement of control circuit boards and solid state switching devices. Electrical input and output termination shall be top, side or rear access, depending on the kVA rating, with the input termination made to the terminals provided, copper standoff bus or directly to the main input circuit breaker terminals and ground bus. The output termination shall be made to the terminals provided or copper standoff bus, depending on the kVA rating.

2.7 Input Over Current Protection: The AVR shall be provided with an integral, three pole, molded case, manually operated, thermal magnetic input circuit breaker rated at 125% of the full load input current. In addition, the system input current, Phase A, B and C, shall be monitored and digitally displayed. A programmable over current alarm shall be provided.

2.8 Bypass Switch: The AVR shall be provided with an integral break before make rotary bypass switch. The AVR shall be either on line or bypassed with one turn of the switch. On models where the input and output nominal voltages are different, a regulator bypass shall be provided in which the shielded isolation transformer will remain on line to provide voltage transformation and isolation. On models where the input and output nominal voltages are the same, an integral break before make rotary maintenance bypass switch shall be provided to wrap around and isolate the AVR. In this case, an input neutral conductor(s) shall be provided and the bypass switch shall bypass the output neutral, as well as, the phase conductors.

The bypass switch circuitry shall be wired such that it cannot switch the unregulated power directly to the active load. Bypass switch actuation shall trip the AVR input breaker, so that the facility load must then be reconnected using the input breaker.

2.9 Alarms: The AVR shall be provided with an input over/under voltage, input over current, over/under frequency, voltage phase reversal, voltage phase imbalance, output over/under voltage, and output over current alarms. The alarms shall automatically reset upon return to nominal operating conditions. Remote communication of alarms via a contact closure shall be provided. Optional digital communication via RS232 and RS485 shall be made available.

2.10 The AVR shall be provided with individual “Fuse Failure” indicator lights, phase A, B and C, on the front panel for diagnostic purpose. Failure of either fusible links or phase semiconductor fuses shall be indicated.

2.11 The AVR shall be equipped with both an “Output Failure” and “Over Temperature” indicator light on the front of the enclosure to indicate an over temperature condition or an output over/under voltage condition, not caused by the input voltage or frequency being out of range. An input “Input Out of Range” indicator light shall be provided on the meter face to indicate that the input voltage or frequency has exceeded acceptable limits.

2.12 Metering: A digital input meter shall be provided to display line voltages, line currents, frequency, kVA, kW, and power factor. A separate digital output meter shall be provided to display line to line voltages, line to neutral voltages, phase currents and neutral current. Both meters shall have programmable minimum and maximum value set points, recorded in EEPROM. Both meters shall be capable of optional remote communications via RS232 and RS485.

2.13 Input/Output Cable Connections: The AVR shall have provisions for the installation of cable lugs directly to the input/output bus bars or conductors to the input/output terminals provided. The manufacturer shall allow sufficient for up to _____ copper conductors per phase and for the neutral bus or terminal.

2.14 Grounding Cable Lugs: The AVR shall have provisions for the installation of cable lugs directly to the ground bus bar or conductor to the terminal provided. The manufacturer shall allow sufficient spacing for ____ copper grounding conductors.

2.15 Recommended Spare Parts & Tools: As an option, the vendor shall make available one set of manufacturer’s recommended spare parts and one set of any special tools required for routine maintenance and repair work at the site. Provide a complete list with part or serial numbers for future order or replacement if required.

2.16 Ventilation: The AVR isolation transformer shall be designed for convection cooling. If fan cooling is required for the solid state electronic switching devices, air filters shall be provided to mitigate dust infiltration.

2.17 Output Transient Suppression Network: Three phases, using high-energy solid state components with 5-nanosecond maximum response time and a coordinated RC filter network. Connections shall be made at AVR output terminals.

Note: The specified common mode noise attenuation shall be accomplished in front of the transient suppression network via the shielded isolation transformer.

The AVR shall provide Transient Voltage Suppression per IEEE std. 587, categories A and B, UL 1449.

Note: An Input Transient Voltage Surge Suppressor (TVSS) shall be provided external to the AVR to divert high-energy voltage spikes and increase system reliability and life. The input transient suppression (TVSS) shall remain in the circuit when the AVR is in maintenance bypass.

2.18 Cabinets & Enclosures: Welded steel (painted) or reinforced riveted galvanized frame construction in accordance with NEMA 1 class specifications.

2.19 Environmental Requirements: Comply with the following, unless otherwise indicated:

2.19.1 Operating Temperature Range: o to 40 degrees C.

2.19.2 Relative Humidity Range: 0 to 95 percent, non-condensing.

2.19.3 Altitude: Unit operates continuously up to 5000 feet above sea level.

2.19.4 Audible Noise: Maximum allowable noise level shall not exceed 40dB to 50dB on units rated 150kVA and below; 50dB to 60dB on units rated 225kVA through 500kVA and 65dB on units rated 625kVA through 1000kVA, when measured at a three-foot distance.

2.20 Automatic Controls: The control portion of the cabinet containing the circuit boards and connection to the semi-conductor devices shall be separate from the transformer and input/output terminations. Each phase shall be regulated using a single microprocessor controlled circuit board, which shall be interchangeable between phases. A single circuit board shall be interchangeable in units rated 10kVA to 50kVA and another single control circuit board shall be interchangeable in units rated 75kVA to 1000kVA, for ease of service. Once shipped from the factory, the AVR should not require adjustments of its controls to regulate within specifications.

2.21 Transformer Component of AVR: Include the following features:

2.21.1 Comply with UL 1561.

2.21.2 Comply with UL 1561, including requirements for non-sinusoidal load-current-handling capability to the degree defined by the designated K-factor.

2.21.3 Cores: Grain oriented, M6 grade, stressed relieved, non-aging silicon steel.

2.21.4 Coil Insulation: 200 degree C class.

2.21.5 Temperature Rise: Designed for 115 degrees C maximum rise above a 40 degree C ambient.

2.21.6 Output Impedance: 3.0 to 5.0 percent.

2.21.7 Regulation: 2.5 to 4.0 percent maximum at full-resistive load; 6 percent maximum at rated nonlinear load.

2.21.8 Full-Load Efficiency: 96 to 98 percent at rated nonlinear load.

2.21.9 Magnetic Field Strength External to Transformer Enclosure: Less than 0.1 Gauss at 450mm.

2.22 Training and On-site Commissioning: Reserved.

2.23 Submittals: Reserved.