Siemens 3RT20181AK61 Contactors (S00 Size)
Key trade-offs in the 3RT2018 S00 family
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Contact configuration: The seed uses 3PST-NO (3 Form A) while most alternates match this. One alternate (3RT20181AU61) drops to SPST-NO (1 Form A) with only one normally-open pole. Panel builders specifying motor loads requiring three-phase switching must confirm the contact form before substituting.
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Coil voltage selection: The seed operates at 120VAC; alternate coil voltages range from 100VAC (93.5 VAC must-operate) to 480VAC (408 VAC must-operate). Coil power rises from 36VA to 43VA at higher voltages. Mismatched coil voltage destroys the contactor at pickup.
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Operating temperature window: All variants specify 25°C ~ 60°C. This narrow range limits use in unventilated enclosures or environments with heat-generating loads nearby. No variant in this family extends below 0°C or above 60°C.
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Operate time divergence: The seed specifies 33 ms; alternates list 35 ms. At motor inrush currents, a 2 ms difference is immaterial, but applications requiring precise sequencing across multiple contactors should treat these as functionally equivalent—not identical.
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Must-operate voltage ratios: The seed requires 96 VAC pickup on a 120VAC coil (80% of nominal). Higher-voltage variants show similar 80–85% must-operate ratios. Drop-out performance depends on the specific control circuit; field verification is not replaceable by catalog data.
Contact form and mounting
- Contact form: 3PST-NO (3 Form A), 16 A rated
- Mounting: Chassis mount or DIN rail, S00 frame
- Coil: 120VAC, 36VA inrush
Technical specifications
| Spec | Value |
|---|---|
| Base PN | 3RT2018 |
| Contact rating | 16 A |
| Coil voltage | 120VAC |
| Coil power | 36VA |
| Must operate | 96 VAC |
| Operate time | 33 ms |
| Operating temp | 25°C ~ 60°C |
| Mounting | Chassis, DIN rail |
Family comparisons
Readers must qualify all alternates independently against their specific load and control scheme.
| MPN | Coil Voltage | Contact Form | Coil Power | Operate Time |
|---|---|---|---|---|
| 3RT20181AK61 (seed) | 120VAC | 3PST-NO | 36VA | 33 ms |
| 3RT20181AK610UA0 | 120VAC | 3PST-NO | 36VA | 35 ms |
| 3RT20181AK62 | 120VAC | 3PST-NO | 36VA | 35 ms |
| 3RT20181AK643MA0 | 120VAC | 3PST-NO | 36VA | 35 ms |
| 3RT20181AR61 | 440VAC | 3PST-NO | 43VA | 35 ms |
| 3RT20181AG61 | 110VAC | 3PST-NO | 43VA | 35 ms |
| 3RT20181AV61 | 480VAC | 3PST-NO | 43VA | 35 ms |
| 3RT20181AN61 | 220VAC | 3PST-NO | 43VA | 35 ms |
| 3RT20181AU61 | 277VAC/DC | SPST-NO | 43VA | — |
3RT20181AK610UA0: same 120VAC/36VA coil and contact rating; only packaging differs (box vs bulk). Suitable for identical control schemes with different quantity packaging preferences.
3RT20181AK62: matches 120VAC/36VA but changes auxiliary contact type from SCR-coded to NC. Panels requiring fail-safe (normally closed) auxiliary monitoring should confirm the auxiliary designation before ordering.
3RT20181AK643MA0: same coil but adds 2NO/2NC auxiliary contact complement. Applications requiring discrete status feedback for both start and stop commands may prefer this variant over the single-SCR auxiliary.