What this control unit does in a TeSys U starter
The LUCA1XBTQ is a standard control unit for the TeSys U motor-starter system. It handles basic protection requirements: overload, short-circuit, phase failure, phase imbalance, and earth fault. The 24 V AC control circuit draws 70 mA sealed (90 mA with larger LUB power bases) and opens the power poles in 35 ms. That 35 ms opening time means the starter clears a fault fast enough to limit let-through energy on a 0.25 kW motor at 400 V — the typical rating here.
The unit plugs into the front face of a TeSys U power base (LUB12, LUB32, or LUB38). No DIN-rail space consumed beyond the base itself. Dimensions are 45 mm wide, 66 mm high, 60 mm deep — the depth is the projection from the power-base face, so plan for 60 mm clearance in front of the DIN rail. IP20 on the front panel and wired terminals; IP40 outside the connection zone.
Rated for AC-44, AC-41, and AC-43 utilisation categories per IEC 60947-6-2. AC-44 is the toughest — switching motors with frequent inching and plugging. The tripping threshold is 14.2 x Ir ±20%, which means the magnetic short-circuit release picks up at roughly 14 times the set overload current.
Compliance and environmental tolerance
Certified to EN/IEC 60947-6-2, UL 60947-4-1, and CSA C22.2 No 60947-4-1 (with phase barrier). Rated insulation voltage 690 V (IEC) / 600 V (UL/CSA). Safe separation of control and main circuits at 400 V SELV. Fire resistance of 960 °C on live-part supports, 650 °C elsewhere. TH protective treatment per IEC 60068 for tropical environments. Immunity to microbreaks up to 3 ms and voltage dips down to 70% for 500 ms — keeps the starter online through brief line disturbances.