Siemens 3RT20271BB443MA0 Contactor
Engineering trade-offs in S0 DC coil contactor selection
- The 24VDC coil draws 245.8 mA (5.9W); coil heating and supply voltage drop affect pull-in margin. Must-operate voltage of 19.2 VDC leaves only 4.8 VDC headroom—a marginal supply or long cable runs reduce reliability.
- The "2NO/2NC" auxiliary contact arrangement is fixed by the suffix code; other suffixes (BB40, BB401AA0) offer only 1NO/1NC, which may be insufficient for seal-in or diagnostic circuits.
- Bulk packaging (seed) versus box packaging (alternates) affects stocking and automation-compatible orientation; bulk units ship without individual box labeling.
- The 3RT2 family shares a 45 mm DIN rail footprint; however, 32A versus 50A current ratings across suffixes determine thermal derating at elevated ambient temperatures.
- Siemens S0 contactors are sized for IEC AC-3 utilization; DC resistive loads at rated current require derating or verification per application.
Coil and contact specifications (3RT20271BB443MA0)
| Parameter | Value |
|---|---|
| Coil Voltage | 24VDC |
| Coil Power | 5.9W |
| Coil Current | 245.8 mA |
| Coil Resistance | 97.6 Ω |
| Must Operate Voltage | 19.2 VDC |
| Contact Rating (AC-3) | 32 A |
| Contact Form | 3PST-NO (3 Form A) + 2NO/2NC aux |
| Mounting | Chassis Mount, DIN Rail |
| Base Product Number | 3RT2027 |
The auxiliary contact complement (2NO + 2NC) exceeds the common 1NO/1NC variants in the same series.
Comparison against similar Siemens S0 contactors
Readers must verify specifications independently for each variant. The table omits lead time, stock, and lifecycle data not present in the records.
| Spec | 3RT20271BB443MA0 | 3RT20271BB44 | 3RT20271BB400UA0 | 3RT20271BB401AA0 |
|---|---|---|---|---|
| Coil Voltage | 24VDC | 24VDC | 24VDC | 24VDC |
| Contact Rating | 32 A | 32 A | 50 A | 32 A |
| Aux Contacts | 2NO/2NC | 2NO/2NC | 1NO/1NC | 1NO/1NC |
| Mount | DIN Rail | DIN Rail | DIN Rail | DIN Rail |
| Coil Power | 5.9W | 5.9W | 5.9W | 5.9W |
| Encapsulation | Bulk | Box | Box | Box |
| Similarity | — | 1.0 | 1.0 | 1.0 |
- 3RT20271BB44 shares the same 2NO/2NC auxiliary count and bulk packaging; differs only in individual-box versus bulk packaging.
- 3RT20271BB400UA0 offers a higher 50 A contact rating but drops to 1NO/1NC auxiliaries; useful when more main-pole current is needed but auxiliary logic is minimal.
- 3RT20271BB401AA0 matches the 32A rating and 24VDC coil while reducing auxiliary contacts to 1NO/1NC, potentially simplifying the control circuit footprint.