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→5.4 Thermostatic Bimetals
The wide variety of thermostatic bimetal types is specified mostly through DIN 1715 and/or applicable ASTM standards (Table 5.23). The different types have varying material compositions for the active and passive side of the materials. The mostly used alloys are iron-nickel and manganese-copper-nickel. Mainly used in circuit protection switches (i.e. circuit breakers) some thermo-bimetals include an intermediate layer of copper or nickel which allows to design parts with a closely controlled electrical resistance.
Table 5.23: Partial Selection from the Wide Range of Available Thermo-Bimetals
====5.4.1 Design Formulas====
For the design and calculation of the most important thermostatic-bimetal parts formulas are given in Table 5.24. The necessary properties can be extracted for the most common materials from Table 5.23. The values given are valid only for a temperature range up to approximately 150°C. For higher temperatures data can be obtained from the materials manufacturer.
Table 5.24: Design Formulas for Thermostatic Bimetal Components (ganz große Tabelle!)
====5.4.2 Stress Force Limitations====
For all calculations according to the formulas in Table 5.24 one should check if
the thermally or mechanically induced stress forces stay below the allowed
bending force limit. The following formulas are applicable for calculating the
allowable load (Force P<sub>max</sub> or momentum M<sub>max</sub>):
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