Siemens 3RT20251AK60 Size S0 Contactor
Where the 3RT20251AK60 Fits in a Motor Branch
The 3RT20251AK60 is a Siemens Size S0 electromechanical contactor intended for use in motor branch circuits and auxiliary control circuits within industrial enclosures. This unit combines a 3-pole power switching section with integral auxiliary contacts, supporting both motor load switching and auxiliary signal functions on a single device. The S0 frame places it in Siemens' compact power class, and the "K" in the type designation indicates the included auxiliary contact configuration of one normally open and one normally closed contact.
Key Specifications
| Parameter | Value |
|---|---|
| Base Product Number | 3RT2025 |
| Coil Voltage | 120 VAC |
| Contact Form | 3PST-NO (3 Form A) |
| Contact Rating (Current) | 40 A |
| Must Operate Voltage | 96 VAC |
| Coil Power | 68 VA |
| Operate Time | 38 ms |
| Operating Temperature | 25°C to 60°C |
| Mounting Type | Chassis Mount, DIN Rail |
| Features | Auxiliary Contacts |
| Encapsulation | Bulk |
Auxiliary Contact Configuration
The integrated auxiliary contacts provide one normally open (NO) and one normally closed (NC) contact pair. This configuration supports common control circuit schemes where both permissive and interlock signals are required without adding a separate auxiliary relay block.
Coil and Operating Parameters
The 120 VAC coil draws 68 VA during inrush and operates reliably when the applied voltage reaches 96 VAC. The contactor achieves full operate in approximately 38 ms, a timing characteristic consistent with general-purpose motor control applications where moderate switching speed is acceptable.
Power Pole Rating
The three-pole main contact section carries a 40 A contact rating under the stated operating conditions. This rating defines the current-carrying capacity of the power poles in the context of the S0 frame thermal limits.
Comparing In-Catalog Alternatives
The table below presents a side-by-side catalog comparison of the primary part with three highest-similarity in-catalog options. These are catalog peers requiring the reader's own qualification — they are not OEM-approved substitutes.
| Parameter | 3RT20251AK60 | 3RT20251AK601AA0 | 3RT20251AK64 | 3RT20251AU60 |
|---|---|---|---|---|
| Contact Rating (A) | 40 | 17 | 17 | 17 |
| Coil Voltage | 120 VAC | 120 VAC | 120 VAC | 277 VAC |
| Must Operate Voltage | 96 VAC | 96 VAC | 96 VAC | 235.5 VAC |
| Contact Form | 3PST-NO | 3PST-NO | 3PST-NO | 3PST-NO |
| Coil Power (VA) | 68 | 67 | 67 | 73 |
| Operate Time (ms) | 38 | 40 | 40 | 40 |
| Operating Temp | 25–60°C | 25–60°C | 25–60°C | 25–60°C |
| Aux Contacts | Yes | Yes | Yes | Yes |
| Mounting | Chassis/DIN | Chassis/DIN | Chassis/DIN | Chassis/DIN |
| Similarity | — | 1.0 | 1.0 | 0.96 |
Why the similarity-1.0 peers are catalog-close
-
3RT20251AK601AA0 shares the same coil voltage, contact form, and auxiliary contact feature set; the similarity reflects near-identical alphanumeric prefix and parameter overlap across the listed fields. The contact rating differs (40 A vs 17 A) and the encapsulation is listed as Box rather than Bulk.
-
3RT20251AK64 also matches on coil voltage and contact form; the primary catalog difference is the auxiliary contact count — this part carries two NO and two NC auxiliary contacts instead of one of each, expanding control flexibility at the cost of a different aux configuration code.
Why 3RT20251AU60 is catalog-similar at 0.96
This part shares the same base product number, contact form, auxiliary contact feature, and mounting type. The coil voltage is 277 VAC instead of 120 VAC, and the must-operate voltage scales proportionally. The contact rating (17 A) differs from the primary part's stated 40 A rating.
FAQ
What is the auxiliary contact arrangement on the 3RT20251AK60? The 3RT20251AK60 includes one normally open (NO) and one normally closed (NC) integral auxiliary contact.
What mounting options does the 3RT20251AK60 support? The contactor is listed for both chassis mount and DIN rail mounting.
What is the must-operate voltage for the 3RT20251AK60 coil? The coil requires at least 96 VAC to pull in reliably at the rated operating temperature range.