2,808
edits
Changes
→13.4.2.2 Temperature Rise
For the assessment of contact materials a temperature rise test is frequently performed after a specified number of switching operations accompanied by arcing (Fig. 13.13). The most important characteristic is the measured temeperature rise of the movable bridge contacts. If a certain upper limit of temperature is reached, adjacent plastic components may be irreversibly damaged.
====13.4.2.3 Analysis of the Switching Sequence====
In switching devices, which are actuated by AC actuator magnets, the contact parts can close and open synchronously at a specific phase angle relative to the voltage-zero of the supply voltage. Of similar importance is the sequence of closing and opening of the contacts with regards to the three phases. The closing and opening delays define at which time delay after the first phase (or pole) the other phases close and open.
Relevant experiments have shown that combined effects of synchronism, phase sequence and switching delay can, under severe adverse conditions,
lead to extreme damage, especially on at least one of the phases or poles. They are the cause of early failure of this phase and therefore the complete switching device and can happen as early as after only 30% of the normally expected lifetime. Because of variations in the mechanical characteristics of switching devices from manufacturing processes life testing cannot be performed on one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and off-switching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, is it possible to assess a specific contact material from a test in only one device alone. Only statistical analysis of tests from multiple device samples can be used as reliable results. Such a procedure is however time consuming and costly. If however every single switching operation during a test is monitored for bounce behavior, on- and offswitching synchronization and related phase sequencing and phase delays, the arc moving behavior, and especially arc energy which is transferred during make and break arcing to the contact pieces, and then these data are properly analyzed, is it possible to assess a specific contact material from a test in only one device.
