Replacement current transformers for SP / SPS / SPS2 / SF6 power circuit breakers
04/01/2013 - Volume IV - Issue I
Current transformers (CTs) on the SP / SPS / SPS2 circuit breakers are enclosed in a die cast aluminum housing which has provided many years of trouble free protection for the active CT element which is encapsulated in resin.
All CTs are manufactured with an external terminal box that facilitates change-out and replacement applications without the need to replace the CT leads, reducing the potential wiring issues at the CT terminal blocks. The CT leads and terminals on most SPS2 circuit breakers have been color coded as well.
CTs are manufactured with an external terminal box that facilitates change-out and reduces potential wiring issues.
For especially corrosive environments, an anodized CT housing successfully completed five thermal cycles between 105C and -40C and another five cycles between 105C and -50C with no de-bonding between the resin and the aluminum housing.
New CT design: Non-anodized (left) vs. Anodized (right)
Siemens successfully completed ASTM B-117 salt spray tests on both the anodized and unanodized CT housings to provide comparative corrosion resistance. The anodized CT housing was found to be far superior.
CT housings are anodized per MIL Std. A-8625, Type II. Anodizing is an electrolytic passivation process used to increase the natural protective oxide layer on aluminum parts. Anodizing seals the pores of the aluminum and provides a good bonding surface for the encapsulating resin.
Anodized aluminum resists corrosion from ambient weather in nearly all locations except in the presence of strong acids (pH<3) or strong bases (pH>8.5) and is used in a variety of automotive and architectural applications.
*Above ratings are most common. Other ratings available. When contacting the Siemens power circuit breaker factory, please have circuit breaker serial number.
Note: CT mounting kits also required (each kit contains parts required to mount three CTs)