The Siemens SITAS 4AM3842-5AJ10 converts 400V AC line-to-line voltage from a three-phase industrial supply down to 110V AC for control circuits, delivering 1.45A at 160VA continuous rating. It is the primary-side voltage counterpart to the 4TJ10 series (230V primary), enabling the same 110V control architecture in panels fed from 400V three-phase mains common across European industrial facilities.

400V Three-Phase Line to 110V Control

Connected across two phases of a 400V three-phase supply, the transformer provides a single-phase 110V output for contactor coils, timer relays, indicator lamps, and control logic. The ±5% primary taps (380/400/420V) accommodate variations in the three-phase supply, maintaining stable 110V output. The 110V secondary conforms to reduced low voltage safety standards, commonly used in UK and railway control systems even when the primary feed is 400V European industrial power.

490VA Surge Capacity for Contactor Holding

The S6 short-time rating of 490VA — three times the continuous rating — ensures that contactors remain firmly seated during motor starting surges. Voltage sag on the control circuit during inrush can cause contactor dropout, leading to motor chattering and contact welding. The 4AM3842-5AJ10 prevents this failure mode in motor control center applications.