The ABB CT‑SDE 1SVR550217R4100 is a single‑function electronic time‑relay belonging to ABB’s “CT‑E” timer family. It is designed to provide a star‑delta (star‑triangle) time‑delay function — typically used for motor starting circuits that need to begin in “star” configuration, then automatically switch to “delta” after a preset time. The relay allows a delayed change‑over when starting motors, which reduces the starting current and mechanical stress. It is compact, DIN‑rail mountable, and uses screw‑terminal connections. The device offers a small mechanical footprint, making it suitable for control panels, motor control centers (MCC), automation cabinets, or motor‑starter assemblies
