The Schneider Electric LUCA05BTQ is a standard control unit within the TeSys U range, designed for basic motor protection and control of a 3-phase motor with self-cooled load type. It provides overload and short-circuit protection, plus earth fault and phase failure sensitivity, in a plug-in (front face) format that integrates into a TeSys U starter base. Rated at 1.5 kW at 400...440 V AC 50/60 Hz, 2.2 kW at 500 V AC, and 3 kW at 690 V AC, the unit's thermal overload class 10 (per IEC 60947-6-2 and UL 508) means it will trip within 10 seconds at 7.2× the set current — standard for protecting general-purpose induction motors against locked-rotor conditions without nuisance tripping on normal starts. The control circuit runs on 24 V AC (20...26.5 V operating range, 14.5 V drop-out), drawing 70 mA RMS sealed or up to 220 mA during closing depending on the power base (LUB12/32/38). Operating time is 35 ms opening and 70 ms closing, consistent across all three compatible power bases.
The tripping threshold is 14.2 × Ir ± 20 %, meaning the magnetic short-circuit release will fire at roughly 14 times the full-load current setting — fast enough to clear a bolted fault before the power base contacts weld. The unit also offers immunity to microbreaks up to 3 ms and voltage dips down to 70 % for 500 ms, so momentary line sags won't drop out a running motor unnecessarily. Safe separation of 400 V SELV between control/auxiliary and main circuits means the 24 V AC control loop is isolated from line voltage — safe for PLC outputs and panel wiring without extra isolation relays. Utilisation categories AC-41, AC-43, and AC-44 cover resistive, motor, and lightly inductive loads respectively. The unit is certified to EN 60947-6-2, IEC 60947-6-2, UL 60947-4-1 (with phase barrier), and CSA C22.2 No 60947-4-1 (with phase barrier) — so it's accepted in North American and European panels without additional testing.
The LUCA05BTQ plugs into the front face of a TeSys U power base (LUB12, LUB32, or LUB38) which then snaps onto a DIN rail. IP20 on the front panel and wired terminals, IP40 on the front face outside the connection zone; suitable for enclosed panels where the front face is operator-accessible. Heat dissipation is 2 W with the LUB12 power base, 3 W with LUB32 or LUB38. In a densely packed panel, that's low enough to avoid forced ventilation for a single starter, but worth summing across a multi-starter group to stay within enclosure thermal limits.
No cross-reference or second-source exists within the TeSys U family — the LUCA05BTQ is the specific 24 V AC standard control unit; the LUCA05B is the 24 V DC variant, and the LUCA05F is the 110...240 V AC version. If your BOM calls for 24 V AC, this is the one.