Mitsubishi S-T10 Magnetic Contactor, 9 A AC-3, 36 mm

A 36 mm-wide AC-operated contactor for small motor circuits

The Mitsubishi Electric S-T10 is the smallest contactor of the MS-T series: a three-pole, AC-operated magnetic contactor that is 36 mm wide, 75 mm high and 78 mm deep. It switches a three-phase squirrel-cage motor of up to 4 kW at 380-440 V (9 A in utilisation category AC-3), or 2.5 kW at 220-240 V (11 A), and carries a conventional free-air thermal current of 20 A. One normally open auxiliary contact is built in as standard.

Mitsubishi Electric describes the T10 frame as more than 16 percent narrower than its earlier 43 mm class, based on its own survey of September 2016, so five units fit in 180 mm instead of 215 mm. That saving matters in compact motor control centres, packaged skids and machine panels where DIN-rail space is the limit. The contactor is open type and clips onto an IEC 35 mm rail or is fixed by screws.

Technical specifications

Choosing coil voltage, auxiliary contacts and overload relay

Orders are written as the model name, the operating coil designation and the auxiliary contact arrangement, with a space between each item. The catalogue gives the example “S-T20 AC200V 2A”; for this frame the equivalent form is S-T10 followed by a coil code such as AC24V, AC100V, AC200V or AC400V. Each coil code covers a voltage band, so AC200V accepts 200 to 240 V at 50 or 60 Hz, and the rating printed on the product follows the band even if a single voltage was ordered. A surge-absorber variant is ordered by adding SA to the type name (S-T10SA), which fits a varistor on the coil.

Front and side clip-on auxiliary blocks (UT-AX4, UT-AX2, UT-AX11) add contacts, and the UT-ML11 mechanical interlock joins two S-T10 units into a reversing pair with an electrical interlock contact. For motor protection the matching 2-element thermal overload relay is the TH-T18 relay (TH-T18KP with 3 elements), set to the motor full-load current; a lower ambient temperature than 20 C raises the trip current, so correct the setting as the catalogue curves describe. For a comparable 9 A contactor from another maker, see the ABB AF09-30-10-11.

Confirm before ordering: the coil designation and frequency, the auxiliary contact arrangement (1a or special 1b), whether the BC finger-safe cover or a surge absorber is wanted, the motor rating and duty category (AC-3 or AC-4), and the short-circuit protective device. Keep the main terminal screws tightened within 0.9 to 1.5 N.m and re-torque periodically, as the catalogue instructs.

MS-T contactor frames compared

The same series continues through eleven frame sizes, each with its own sibling model. The table lists the AC-3 operational current at 380-440 V and the thermal current from the catalogue.

Documents and quotation

The attached document is an excerpt of Mitsubishi Electric catalogue L(NA)02030ENG-K covering the series introduction, selection tables, making and breaking capacities, coil ratings, certification pages and the order procedure. Send the full type name with coil code, the quantity and the delivery location to receive a quotation from Seven Star LLC, an independent supplier in Muscat.