{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3VA9978-0AA22","brand":"Siemens","brandSlug":"siemens","productSlug":"3VA9978-0AA22","canonicalUrl":"https://aoctrl.com/siemens/3VA9978-0AA22","factsUrl":"https://aoctrl.com/api/mcp/products/3VA9978-0AA22","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 3VA9978-0AA22, leading auxiliary switch, changeover contacts type HQ (7 mm), 6 A thermal current, for 3VA4/5/6 circuit breakers.","salesMarkdown":"## What this auxiliary switch does in the panel The Siemens 3VA9978-0AA22 is a leading auxiliary switch — a changeover contact block that mounts onto SENTRON 3VA4, 3VA5, and 3VA6 molded-case circuit breakers. Its job is to signal the breaker's ON/OFF position back to a PLC, a status lamp, or a safety circuit, so the control system knows whether the power path is closed or open. The switch contacts are physically linked to the breaker's operating mechanism, so the signal follows the main contacts without relying on a separate sensor. The thermal current rating (Ith) is 6 A, which is the continuous current the switch can carry through its closed contacts without overheating. That's the ceiling for the signal circuit, not the load circuit — you'd wire a 24 VDC PLC input or a 120 VAC indication lamp through these contacts, not a motor or heater. It fits the same environment the 3VA breaker lives in. ## Switching capability by load type and voltage The switch's real-world capability depends on the load type and control voltage. For solenoid and contactor coils (AC-15), the rating drops to 3 A across the same voltage range — the inrush current of an inductive coil is what limits the contact life, not the steady-state current. On DC circuits, the ratings are more voltage-sensitive because DC arcs are harder to extinguish. At 24 V DC, the switch handles 4 A for resistive loads (DC-12) and 0.8 A for inductive loads (DC-13). At 48 V DC, those numbers drop to 2 A and 0.4 A respectively. At 110 V DC, the DC-13 rating is just 0.2 A; at 250 V DC, it's 0.1 A. If you're switching a DC solenoid or brake coil at 24 V, keep the coil current under 0.8 A — that's the rating that governs contact life. ## Mechanical fit and wiring This is a leading auxiliary switch with changeover (HQ) contacts in a 7 mm-wide format. It snaps onto the left side of the 3VA4/5/6 breaker frame. The stripped length for wiring is 15 mm (0.6 in), which is standard for spring-cage or screw terminals on SENTRON accessories. The switch's operating time relative to the main contacts is 20 ms — it signals the breaker position within one AC cycle. That's fast enough for most PLC scan cycles, but if you need near-instantaneous feedback for a safety-rated circuit, verify the response time against your safety relay's requirements.","metaTitle":"Siemens 3VA9978-0AA22 Leading Auxiliary Switch, SENTRON, 6 A","metaDescription":"Siemens 3VA9978-0AA22 leading auxiliary switch for 3VA4/5/6 breakers. 6 A thermal, AC-15 3 A / DC-13 0.8 A at 24 V. Active production, quoted to order. Pollution degree 3, 4 kV sur","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Circuit Breaker Accessories"],"specifications":{"title":"3VA9978-0AA22","Maximum":"16","Minimum":"20","Accessories":"Leading auxiliary switch","description":"leading changeover switch changeover contacts type HQ (7mm) accessory for: 3VA4/5/6","Stripped Length":"15 mm","Thermal Current":"6 A","lifecycle_stage":"current","Product Brand Name":"SENTRON","at AC-12 / at 12 V":"6 A","at AC-12 / at 24 V":"6 A","at AC-12 / at 48 V":"6 A","at AC-15 / at 12 V":"3 A","at AC-15 / at 24 V":"3 A","at AC-15 / at 48 V":"3 A","at DC-12 / at 12 V":"6 A","at DC-12 / at 24 V":"4 A","at DC-12 / at 48 V":"2 A","at DC-13 / at 12 V":"1 A","at DC-13 / at 24 V":"0.8 A","at DC-13 / at 48 V":"0.4 A","Degree Of Pollution":"3","Product Designation":"Leading auxiliary switch","at AC-12 / at 125 V":"6 A","at AC-15 / at 125 V":"3 A","at DC-12 / at 110 V":"0.5 A","at DC-12 / at 250 V":"0.25 A","at DC-13 / at 110 V":"0.2 A","at DC-13 / at 250 V":"0.1 A","Overvoltage Category":"III","Stripped Length [In]":"0.6 in","Design Of The Product":"Accessories for 3VA circuit breakers","at AC-12 / at 220/240 V":"6 A","at AC-15 / at 220/240 V":"3 A","Surge Voltage Resistance":"4 kV","Lead Time / Relating To Main Contacts":"20 ms","operating voltage / at DC / rated value / minimum":"250 V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/744e0f28344d9325d75092a75debf0b9.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=650506&mlfb=3VA9978-0AA22"},"ai":{"faq":[{"question":"Will 3VA9978-0AA22 fit a 3VA2 or 3VA1 breaker?","answer":"No, this leading auxiliary switch is designed specifically for SENTRON 3VA4, 3VA5, and 3VA6 molded-case circuit breakers. It does not fit the 3VA1 or 3VA2 frame sizes."},{"question":"What is the difference between this leading switch and a standard auxiliary switch?","answer":"A leading auxiliary switch changes state slightly before the breaker's main contacts open or close (20 ms lead time per the spec), so it can signal impending status changes. A standard auxiliary switch follows the main contacts directly. This matters for sequencing logic where the control system needs to know the breaker is about to trip before the load circuit actually drops."},{"question":"What compliance documentation does Siemens provide for 3VA9978-0AA22?","answer":"As a SENTRON accessory, this switch carries Siemens' standard compliance documentation including CE marking for the European market. Specific declarations (RoHS, REACH, UL) should be requested at quote time from the supplier, as they vary by manufacturing date and destination."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3VA9978-0AA22","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/3VA9978-0AA22 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-22T19:47:38.189Z","lastPublished":"2026-07-22T19:47:38.189Z","indexable":true}}