Abstract
In 1944, the hottest spot temperature allowance for ventilated dry-type transformers was established as 30/spl deg/C for 80/spl deg/C average winding temperature rise and IEEE standards use a constant 30/spl deg/C hottest spot temperature allowance for all insulation temperature classes and all transformer ratings. Thermal tests under different loading conditions were performed on a prototype 2500 kVA ventilated dry-type transformer and six full-size test coils with imbedded thermocouples in the windings. The test data indicated that the hottest spot temperature allowance used in IEEE and IEC standards is too low for ventilated dry-type transformers above 500 kVA. It is impossible to design ventilated dry-type transformers above 500 kVA with an average temperature rise of 150/spl deg/C exceeding the permissible hottest spot temperature rise of 180/spl deg/C due to large thermal gradients. The average temperature rise for ventilated dry-type transformers above 500 kVA with 220/spl deg/C insulation temperature class should be 120/spl deg/C. IEEE standards should require measurement of hottest spot temperature rise on prototype transformers or windings as a design test to qualify a design family and the manufacturer's mathematical models. This is especially important for ventilated dry-type transformers rated for nonsinusoidal load currents. The specification suggested in the paper should be used until IEEE standards are revised.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.