The TA25DU25-20 is a 25 A, 3-pole thermal overload relay from Eaton's A-Line series, rated for 600 VAC. It protects motors against sustained overcurrent by tracking the thermal load on the winding — the bimetallic strip inside mimics the motor's heating curve, so nuisance tripping on harmless inrush is minimized.
The 25 A rating is the full-load current setting — match it to the motor nameplate FLA. The thermal element responds to the heating effect of the actual load current, so ambient temperature in the panel affects the trip point; if the enclosure runs hot, the relay will trip earlier than the dial setting suggests. Standard practice is to mount it directly to the contactor output side, sharing the same DIN rail.