Siemens 3RV2742-5FD10 SIRIUS 3RV2 motor starter protectors. Siemens 3RV2742-5FD10 is the exact printed commercial reference for a motor protection circuit breaker in the SIRIUS 3RV Motor Protection range. Siemens' official product description is: circuit breaker size S3 for system protection with approval circuit breaker UL 489, CSA C22.2 no. 5-02 thermal release 35 A short-circuit release 455 A screw terminal.