The Siemens 3RB1900-3B is a sealable cover designed for 3RB series overload relays. Its job is to cover the current setting screw and immobilize the manual/automatic reset selector, preventing unauthorized or accidental adjustment of the trip current setting or reset mode after commissioning.
Deployment context
This cover snaps onto the front of a 3RB overload relay mounted in a control panel or motor starter enclosure. Once fitted and sealed (typically with a lead seal or tamper-evident wire through the cover's hasp), it locks the current-setting potentiometer and the reset-mode switch in their commissioned positions. Common on food-and-beverage, pharmaceutical, or any line where a quality audit or safety inspection requires proof that settings have not been changed since the last verification.
What it is not
This is a mechanical accessory — no electrical ratings, no wiring, no contacts. It does not alter the overload relay's trip curve, auxiliary contact state, or communication address. Its only function is physical security of the two front-panel adjustments.