Change or Time Constant with Transformer Load

Whitman, L. C.

doi:10.1109/aieepas.1962.4501415

Cited by 6 publications

(1 citation statement)

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“…Nevertheless, (8) turns out to be adequate as long as the ambient temperature is constant, and as long as the parameter is not too different from unity. With regard to the latter, a long-standing "correction factor" applied to the time constant has been used [13]. This does indeed make the solution better, but not properly accurate, since the problem is not with the time constant itself but with the shape of the solution curve.…”

Section: Appendix a Comparison With The C5791-1995 Equationsmentioning

confidence: 99%

A fundamental approach to transformer thermal modeling. I. Theory and equivalent circuit

Swift¹,

Molinski

Lehn

2001

IEEE Trans. Power Delivery

368

187

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A simple equivalent circuit to represent the thermal heat flow equations for power transformers is presented. Key features are the use of a current source analogy to represent heat input due to losses, and a nonlinear resistor analogy to represent the effect of air or oil cooling convection currents. An interesting historical note concerns the fact that the foregoing effect was first quantified in 1817. It is shown that the idea of "exponential response" is not the best way to think of the dynamics of the situation. It is also shown that one can consider ambient temperature to be a variable input to the system, and that it is properly represented as an ideal voltage source. Physical experimental verification, on an in-service 250 MVA transformer, is described in a companion paper.

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Section: Appendix a Comparison With The C5791-1995 Equationsmentioning

confidence: 99%