MTBF / SIL / Failure Rate

It is difficult to assign MTBF to contactors because their performance depends heavily on each individual system, application, and usage.  Factors that impact the life cycles and dependability of a contactor include, but are not limited to: system voltage, amount of power on break, amount of power on make, level of inductance, level of capacitance, fault currents (short circuit), environmental operating temperature, thermal cycling, shock and vibration, cable or busbar size and length, fastening method, and various other factors.

To provide a rough approximation of MTBF, one should take the number of mechanical cycles from the data sheet, at the anticipated voltage and current switching level, and divide it by the average number of cycles expected per day.  This assumes the contactor will be used within all of the limits and specifications as defined on the data sheet and that the load is resistive.  If the contactor is switching a capacitive or inductive load it can significantly reduce the overall life of the contactor.  GIGAVAC defines contactor end-of-life when the insulation resistance as measured between the main terminals drops below 10 Mohm.  Customers are encouraged to test under the specific conditions of their application to determine product suitability.