What this MCCB is and what it does
The Siemens SENTRON 3VA1340-5EF32-0DG0 is a 3-pole molded case circuit breaker (MCCB) rated for 400 A at 40 °C ambient, with a TM240 thermal-magnetic overcurrent release. It provides fault protection and isolation for power distribution in industrial switchboards, panelboards, and motor control centers. The interrupting capacity reaches 187 kA at 240 V, 121 kA at 415 V, and 75.6 kA at 500 V, dropping to 11.9 kA at 690 V. These ratings define the maximum fault current the breaker can safely clear at each voltage level — critical for coordination studies and SCCR compliance on the line side. Rated insulation voltage is 800 V, and the breaker dissipates a maximum power loss of 94.6 W at full load, which must be factored into enclosure thermal calculations.
Thermal derating and ambient temperature
The breaker holds its full 400 A rating up to 50 °C ambient. Above that, it derates linearly: 392 A at 55 °C, 384 A at 60 °C, 376 A at 65 °C, and 367 A at 70 °C. This derating curve is the spec to use when the breaker is mounted in a warm enclosure or near other heat sources.
Auxiliary and release configuration
This variant includes an undervoltage release (UVR) and one auxiliary switch plus one trip alarm switch. The UVR trips the breaker when control voltage drops below a threshold, which is standard for machinery safety circuits where loss of control power must open the main disconnect. The auxiliary and alarm contacts provide remote status feedback to a PLC or annunciator panel.
Physical integration
Dimensions are 248 mm high, 138 mm wide, and 110 mm deep. The 3-pole frame mounts into standard switchboard or panelboard cutouts; the 110 mm depth fits typical enclosure depths without interference with the back panel or door-mounted devices.