S00 auxiliary contactor with 2 NO and a 110 V DC coil
The Siemens 3RH2122-2LF40-0LA0 is a SIRIUS auxiliary contactor in frame size S00, carrying 2 normally-open instantaneous contacts and a 110 V DC coil with an integrated varistor surge suppressor. The varistor across the coil suppresses the inductive kick when the DC circuit opens, protecting the PLC output or control relay driving it.
Switching performance and endurance
Mechanical endurance is 30 million operating cycles typical — this is the life of the mechanism before wear, not the electrical life under load, which will be lower at rated current. Switching frequency: 10,000 operations per hour for AC loads; for DC loads the minimum off-time is 7 to 20 ms, which limits the maximum switching rate to about 50 Hz depending on the load time constant.
Environmental limits and wiring
Relative humidity minimum is 10 %; no upper limit stated in the record, but the SIRIUS series typically handles up to 95 % non-condensing in standard industrial environments.
The auxiliary switch extension is available as a separate add-on module, so the 2 NO base can be expanded in the field without replacing the contactor.