The
range of motor protection thermistors are manufactured to conform
to BS4999 Pt. 72. The sensing component is a doped barium titanate
disc approximately 3mm dia. x 1mm thick. The ceramic pellet is
provided
with flying leads and an electrically insulating coating to provide
complete isolation from the motor winding. The rapid increase
in electrical
resistance is set during manufacture to produce a range of components
with "switching" temperatures at 10C intervals from 80C through
to 190C
Tr is reference or "switching" temperature of the device.The specification infers a rate of increase of resistance from Tr - 5° to Tr + 5°of 15% per °C. In practice this will be between 20% and 60%, depending on the type of device Lead Wire 7/.15silver coated copper conductors, P.T.F.E. insulated to BSG 210 Type B (500V working). The lead colours identify the switching temperature of the device , as B.S. approved. Lead length is 500mm as standard. Thermistor Bead Insulation The primary insulation is epoxy resin, with a shrink sleeeve for added mechanical and electrical protection .Devices type T80 or T160 have a "Kynar" sleeve , T170 to T160 have a PTFE sleeve. Insulating Rating Thermistor leads to thermistor bead insulation 2500V.RM.S. Adhesion of soldered joint to ceramic substrate
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