Motor Protection Thermistors

PTC Thermistors can be used on NEMA, Metric and Servos

Price:    $7.88      Singles
            $17.33    *Triplets           $24.15  **Triplets

This range of motor protection thermistors are manufactured to conform to BS49999 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 10˚C intervals from 80˚C through to 190˚C.

Electrical Specification
Temperature                  Resistance                  Test Voltage (DC)

Tr                                     100 ohms Typical              2.5v
Tr -5˚ C                           550 ohms Max.                  2.5v
Tr +5˚ C                          1330 ohms Min.                2.5v
Tr +15˚ C                        4000 ohms Min.                7.5v
-20˚ C to Tr -20˚ C        250 ohms Max.                  0.1v

Tr is the reference or “switching” temperature of the device. The specification infers a rate of increase of resistance from Tr -5˚ to Tr +5˚ of 1.5% per degree Celsius. In practice, this will be between 20% and 60%, depending on the typed of device.

Lead Wire – 7/.15 silver coated copper conductors, P.T.F.E. insulated to BSG 210 Type 8 (500v working). The lead colors identify the switching temperature of the device, as B.S. approved. Lead length is 500mm standard.

Thermistor Bead Insulation – The primary insulation is epoxy resin, with a shrink sleeve for added mechanical and electrical protection. Devices type T80 or T160 have a KYNAR sleeve, T170 to %190 have a PTFE sleeve.

Insulation Rating – Thermistor leads to thermnistor bead insulation 2500v. RMS
Adhesion of soldered joint to ceramic substrate – Without bead insulation – Peel test 500 gms. Shear test 1,000 gms.

Limiting Ratings – Operating temperature range -20˚ C to 180˚ C (or TR +20˚ C, whichever is greater). Maximum voltage for temperatures sensing 2.5v DC