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SECTION 16403 LOW VOLTAGE DISTRIBUTION TRANSFORMERS, DRY TYPE 403.01 GENERAL A. Manufacturers Transformers used for converting the 480-Volt systems voltage to lower voltages shall be dry type, as manufactured by Square D. B. Description 1. Transformer rating and type shall be as shown in the contract documents. All low voltage transformers shall meet the efficiency levels established in Nema TP-1, TP-2 and TP-3 80 C temperaure rise in conncection to energy efficient transformers in accordance with the Claifornia Code of Regulations Title 20 requirement. 2. Transformers shall be rated 480-Volt, 3-phase, 3-wire Delta primary and 120/208-Volt, 3-phase, 4-wire wye secondary. 3. Impedance shall be in accordance with NEMA Standards. All transformers of identical KVA shall have similar impedance ratings. 4. Transformers, 600 volts and below, 500 KVA and below, shall be Underwriter’s Laboratory listed and shall bear the UL label. Transformers shall meet NEMA, IEEE, and ANSI standards. Transformers shall be designed for continuous operation at rated KVA, 24 hours a day, 365 days a year, with normal life expectancy as defined in IEEE #65. This performance shall be obtainable without exceeding 80C average temperature rise in a 40C maximum ambient, and 4% minimum impedance 16403-rev0 5. The transformer shall be capable of withstanding a zero impedance fault, across any or all low voltage bushings, without mechanical or electrical damage. 6. Transformers shall have 2-2 ½% taps above and 4-2 ½% taps below nominal rated voltage. The taps shall be set for nominal rated voltage at the factory. 7. The transformer shall have sound levels equal to or lower than those established in the latest revision of ANSI Standard C89.12.7 2. 16403 - 1 December 2004 SECTION 16403 LOW VOLTAGE DISTRIBUTION TRANSFORMERS, DRY TYPE 8. The transformer enclosure shall meet the Underwriter’s Laboratories specification UL506 for the following: a. Ventilation openings, corrosion resistance, cable bending space, grounding provisions, surface temperatures, wiring compartment temperature rise, and terminations. The transformer case shall be of the self-bracing type. b. The enclosure shall be provided with lifting holes to facilitate handling and installation without removal of any of the enclosure components. c. The terminal compartment shall be located in the bottom of the transformer, below the coil-core assembly, and shall provide for back, bottom, or side conduit entrance. Terminals shall be plainly identified. 9. Transformers 15 KVA and Larger shall be 80 C temperature rise above 40 ambient unless otherwise noted. C. The transformer shall be constructed with core materials of a high quality, low loss nature, in order to minimize exciting current, no-load losses, and inter-laminar vibrations. D. K-RATED TRANSFORMER K-Rated transformers shall be UL listed for use for 50 to 100% NonLinear Harmonic loads. The primary winding shall have sufficient conductor capability to withstand the high circulating harmonic currents which circulate in the data windings. 16403-rev0 1. K-rating of the transformer shall be as shown on the contract documents, the K-rating shall be as defined in ANSI standard C57.110 and UL-1561. 2. Coil Conductors shall have continuous windings with termination's brazed or welded. Individually insulated secondary conductors are arranged to minimize hysteresis and eddy current losses at harmonic frequencies. 3. The transformer shall be designed to compensate for the additional heating effects generated by the harmonic currents of Non-Sinusoidal loads. 4. Winding temperature rise shall not exceed 115 C in 40 C max. ambient. 5. The neutral bus shall accommodate 200% of the rated current. 16403 - 2 December 2004 SECTION 16403 LOW VOLTAGE DISTRIBUTION TRANSFORMERS, DRY TYPE 6. 7. E. Core flux density shall be below saturation at 10% primary over voltage, and with Basic impulse level of 10 kV. The transformer on impedance should be 4% minimum to limit the let through connect to 10KA ELECTROSTATIC ISOLATION TRANSFORMER: The isolation transformer shall protect the system from power line noise and transients. 1. Electrostatic shield shall be of copper, between primary and secondary windings. Shielding shall have low capacitive coupling between input and output. 2. Provide the electrostatic shield with a separate insulated ground connection. 3. The transformer noise rejection shall be 140db for common mode and 60db for normal mode noise with EMF of 0.1 Gauss max. measured at 18" from the noise suppresser. 4. The transformer shall have efficiency of 95% at operating frequency of +/- 2% of 60Hz, and load regulation of 3% or less from no load to full load. ***END OF SECTION 16403*** 16403-rev0 16403 - 3 December 2004