Guide Specification for Ventilated Dry Type Transformer
2. Transformer shall be designed to supply rated current at 100% linear load plus carry the percent of non-linear odd order load up to the 25th harmonic as listed in Table 4.
3. The transformer shall be three-phase with the fundamental frequency rating of 60 hertz.
4. Primary winding shall be delta connected and secondary winding shall be wye connected.
5. The transformer windings and terminals shall be aluminum. (Copper option is readily available; please specify)
7. The temperature rise at the rated voltage and rated K-Factor load shall not exceed 150°C when measured by the resistance method as listed in ANSI/IEEE C57.12.91 with a 220°C UL Component Recognition Insulation System. (Optional: 115°C and 80°C temperature rise K-1 through K-20 Units available; please specify.)
8. The primary and secondary conductor shall be sized; shaped and transposed where necessary, to keep eddy current losses to an absolute minimum. The primary winding conductor also shall be sized to carry the triplen harmonic circulating current effect in the delta winding without overheating.
9. The secondary neutral shall be 2x (twice) the ampacity of the secondary phase conductors for triplens and unbalanced single phase loads.
10. The Basic Impulse Level of all windings shall be 10 KV.
11. The enclosure shall be rated NEMA-1. (Optional: NEMA-3R units available.)
12. Optional: A full electrical width electrostatic shield shall be placed between the primary and secondary windings of each coil. With the shield grounded to a common point and the transformer connected under normal loaded conditions the attenuation of common mode line noise and transients shall be similar to values in Figure 4.
13. The average audible sound level shall comply with NEMA ST-20:
10 to 50 KVA - 45 dB
51 to 150 KVA - 50 dB
151 to 300 KVA - 55 dB
301 to 500 KVA - 60 dB
501 to 700 KVA - 62 dB
701 to 1000 KVA - 64 dB
1001 to 1500 KVA - 65 dB
1501 to 2000 KVA - 66 dB
Note: Lower sound levels may be desirable for critical areas such as hospitals, schools or office areas. Contact your local FPT Representative for specific recommendations.
