# Encyclopedia of magnetics and electromagnetics

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thermal_resistance

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 thermal_resistance [2020/07/19 01:50]stan_zurek thermal_resistance [2020/07/19 01:51]stan_zurek Both sides previous revision Previous revision 2020/07/19 01:51 stan_zurek 2020/07/19 01:50 stan_zurek 2020/07/09 00:17 stan_zurek 2020/07/02 22:35 external edit2017/01/30 15:21 stan_zurek -review2016/01/02 21:59 stan_zurek 2015/02/04 14:12 stan_zurek ref2015/01/27 14:39 stan_zurek +calculator2015/01/22 14:52 stan_zurek 2015/01/22 14:44 stan_zurek created 2020/07/19 01:51 stan_zurek 2020/07/19 01:50 stan_zurek 2020/07/09 00:17 stan_zurek 2020/07/02 22:35 external edit2017/01/30 15:21 stan_zurek -review2016/01/02 21:59 stan_zurek 2015/02/04 14:12 stan_zurek ref2015/01/27 14:39 stan_zurek +calculator2015/01/22 14:52 stan_zurek 2015/01/22 14:44 stan_zurek created Line 37: Line 37: There are several empirical equations linking the size and shape of a given class of devices. For example for [[EE (ferrite)|EE]], [[EI (ferrite)|EI]], [[ETD (ferrite)|ETD]] and [[EC (ferrite)|EC]] ferrite transformers the following formula could be used:[([[http://google.com/books?isbn=9780123865335|Sanjaya Maniktala, Switching power supplies A-Z, 2nd edition, Newnes, 2012, ISBN 978-0-12-386533-5, p. 155]])] There are several empirical equations linking the size and shape of a given class of devices. For example for [[EE (ferrite)|EE]], [[EI (ferrite)|EI]], [[ETD (ferrite)|ETD]] and [[EC (ferrite)|EC]] ferrite transformers the following formula could be used:[([[http://google.com/books?isbn=9780123865335|Sanjaya Maniktala, Switching power supplies A-Z, 2nd edition, Newnes, 2012, ISBN 978-0-12-386533-5, p. 155]])] - |
$R_{th} = 53 · (V_{core})^{-0.54}$
|  (K/W) or (°C/W)  | + |  $$R_{th} = 53 · (V_{core})^{-0.54}$$  |  (K/W) or (°C/W)  | where: //Vcore// - core volume in cm3 (i.e. this the volume of the ferrite core itself as specified by the manufacturer, and not volume of the whole transformer). where: //Vcore// - core volume in cm3 (i.e. this the volume of the ferrite core itself as specified by the manufacturer, and not volume of the whole transformer). Line 47: Line 47: Empirical data given by [[Epcos]] also suggest that the thermal resistance is roughly proportional to the reciprocal of square root (power of -0.5) of the ferrite core volume, which is in agreement with the previous equation:[(Thermal_resistance)] Empirical data given by [[Epcos]] also suggest that the thermal resistance is roughly proportional to the reciprocal of square root (power of -0.5) of the ferrite core volume, which is in agreement with the previous equation:[(Thermal_resistance)] - |
$R_{th} = \frac{x}{\sqrt{V_{core}}}$
|  (K/W) or (°C/W)  | + |  $$R_{th} = \frac{x}{\sqrt{V_{core}}}$$  |  (K/W) or (°C/W)  | - where //x// is the proportionality factor. + where $x$ is the proportionality factor. ===== Importance ===== ===== Importance ===== 