Siemens 3RT1055-6AB36 Contactors

Trade-offs for S6 150A Contactors at 23–26V Coil

For a panel engineer evaluating the 3RT1055-6AB36 series in motor-branch or feeder applications, the following trade-offs emerge from the published ratings:

• 360 W coil burden vs. control-circuit capacity — The pull-in power draw of 360 W requires a control supply capable of delivering that transient; sustained holding power is lower but the inrush demands consideration on narrowVA-rated contactors or PLC outputs.
• 95 ms operate time vs. motor-start coordination — Standard electromechanical contactors exhibit slower operate times than solid-state alternatives; verify that 95 ms is acceptable for the motor starter coordination class intended for the installation.
• 150 A through-fault without auxiliary heater blocks — The contact rating of 150 A applies to the main contacts; applications requiring overload protection need separate sizing of thermal overload relay or electronic motor protective device matched to the motor FLA.
• Bulk packaging vs. field stocking convenience — The seed variant ships in bulk; panel builders ordering just-in-time may prefer box-packaged alternates to simplify shelf inventory at the expense of unit cost.
• 25–60 °C operating range vs. enclosure thermal management — The specified ambient rating of 60 °C maximum means enclosed panel designs must account for internal temperature rise; derating may be necessary in poorly ventilated cabinets.

Engineering verification checklist

• Control voltage range (23–26 VAC/DC) matches available control supply; verify minimum pickup voltage at operating temperature.
• Coil power (360 W) is compatible with the control circuit's interrupt rating and wiring protection.
• 150 A contact rating is appropriate for the motor or feeder load; confirm that starting current does not exceed the contactor's make/break ratings.
• Mounting configuration (chassis or DIN rail) is compatible with the intended enclosure or mounting plate.
• Operate time (95 ms) meets the coordination time requirements for the selected starter scheme.
• Ambient temperature at the contactor location will not exceed 60 °C under worst-case conditions; derate if necessary.
• Main contact form (3PST-NO, 3 Form A) is correct for the three-phase circuit topology.
• Auxiliary contact provision is adequate for the required feedback, interlock, or pilot signalling.
• Mechanical installation clearances comply with IEC 60947-1 spacing requirements for the S6 frame size.