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This legacy Siemens SIRIUS front-mounted auxiliary contact features 1 Normally Closed (NC) contact, compatible with 3TF3 / 3TF4 contactors. Original production discontinued on Oct 01, 2021 with no identical OEM replacement. Recommended drop-in alternative: domestic compatible 3TY7561-1AA00, or upgrade to 3RH2911-1AA01 for 3RT6 series contactors.
- Model Code Breakdown
| Code Segment | Definition |
| 3TX | Base designation for Siemens SIRIUS snap-on front auxiliary contact blocks |
| 4001 | Contact configuration code: 1NC (single normally closed); 4010 = 1NO (single normally open) |
| -2A | Mounting & terminal specs: front snap-in installation, no contact status indicator window, captive screw clamp terminals (exclusively designed for 3TF3/3TF4 contactors) |
| Status | Discontinued from Oct 01, 2021; OEM note: Product was deleted without replacement |
- Core Electrical Specifications
| Item | Value | Remarks |
| Contact Configuration | 1NC, positively driven | Designed for safety circuit compliance |
| Conventional Thermal Current (Ith) | 10 A | Rated continuous operating current |
| AC-15 Breaking Capacity | 5.6 A @ 230 VAC | Breaking capacity for control circuits |
| 3.6 A @ 400 VAC | ||
| 2.2 A @ 690 VAC | ||
| Rated Insulation Voltage (Ui) | 690 V | Maximum permissible operating voltage |
| Impulse Withstand Voltage | 6 kV | Electrical isolation safety rating |
| Mechanical Endurance | 10 million operations | Far exceeds service life of base contactor |
| Electrical Endurance | 1 million operations (AC-15 duty) | Under rated cyclic load |
| Termination | Captive clamping screws | For solid conductors: 0.75~2.5 mm² |
| Ingress Protection | IP20 | Finger-safe & dust-proof |
| Operating Temperature | -25℃ ~ +55℃ | Storage: -55℃ ~ +80℃ |
| Compliance Standards | IEC60947-5-1, GB14048.5 | CE & RoHS certified |
- Full Same-housing Model List (3TX4 Series)
| Order Code | Contact Layout | Mounting Style | Matching Contactor | Status |
| 3TX4001-2A | 1NC | Front snap-on | 3TF30~3TF34 / 3TF40~3TF45 | Discontinued |
| 3TX4010-2A | 1NO | Front snap-on | Same as above | Discontinued |
| 3TX3001-2A | 1NC | Side-mounted | Legacy 3TB contactors | Discontinued |
| 3TX3010-2A | 1NO | Side-mounted | Same as above | Discontinued |
| 3TX4002-2A | 2NC | Front snap-on | High-current 3TF range | Discontinued |
| 3TX4012-2A | 1NO+1NC | Front snap-on | Same as above | Discontinued |
- Full Compatible Contactor List (Exclusive for Front Snap Fit)
Only applicable to below 3TF series, incompatible with newer 3RT / 3RV ranges:
3TF30: 3TF3000~3TF3090 (9A~12A)
3TF31: 3TF3100~3TF3190 (12A~16A)
3TF32: 3TF3200~3TF3290 (16A~25A)
3TF33: 3TF3300~3TF3390 (25A~32A)
3TF34: 3TF3400~3TF3490 (32A~40A)
3TF40~45: 3TF4000~3TF4590 (40A~95A)
> Note: One contactor can mount 1 front block + 2 side auxiliary blocks simultaneously, max expansion up to 6 auxiliary contacts (3NO +3NC).
- Replacement Selection Guide for Obsolete Item
5.1 Direct Drop-in Replacement (No Contactor Modification)
| Replacement PN | Brand | Contact | Compatibility | Advantages |
| 3TY7561-1AA00 | Siemens domestic alternative | 1NC | Identical snap dimension | Plug-and-play, cost-effective |
| 3TX4001-2B | Legacy Siemens | 1NC | Same function with indicator lamp | Obsolete stock only, high cost |
| LC1-D Auxiliary Contact | Schneider Electric | 1NC | Requires adapter bracket | Established brand, stable performance |
5.2 Full Unit Upgrade (3TF → 3RT6)
| Upgrade Option | New Contactor | Matching Auxiliary Contact | Advantages | Application |
| Standard Upgrade | 3RT6026~3RT6036 | 3RH2911-1AA01 (1NC) | Long service life, intelligent monitoring | New construction & equipment retrofit |
| Function Expansion | 3RT6040~3RT6056 | 3RH2911-1AA01 + 3RH2911-1BA01 | Multi-contact combination | Complex control circuits |
- Application Environment & Industrial Cases
✅ Approved Application Scenarios
- Motor Control Circuits: Fault feedback & star-delta interlock for 3TF contactors of fans & water pumps
- PLC Interface: NC contact feeds contactor open/closed status into PLC digital input modules
- Safety Interlock: Emergency stop & access door protection; NC forced opening cuts control supply (compliant with EN 60204-1)
- Status Indication: Pilot lamp power switching; NC opens to turn off indicator when contactor energizes
❌ Forbidden Applications
- Direct main-circuit loading: Designed exclusively for control loops (coils, pilot lamps, PLC signals); never connect to power main circuit
- Harsh ambient: Avoid >60℃, heavy dust, corrosive chemical & non-enclosed cabinets (accelerates contact oxidation)
- High-frequency cycling: >10 cycles/min; use solid-state relays instead
- DC heavy-load circuits: AC-15 rating invalid for DC-13 duty; select dedicated DC auxiliary contacts
Industrial Application Cases
| Industry | Application | Contact Function |
| HVAC | AC compressor contactor | Fault stop signal to building automation system |
| Water Treatment | Water pump motor control | Overload interlock with main contactor |
| General Machinery | Conveyor control | Emergency stop cut-off for safe shutdown |
| Power Distribution | Backup power transfer | Contactor status monitoring to prevent faulty switching |
- Common Fault Troubleshooting
| Fault | Root Cause | Remedy |
| Open circuit / poor contact | 1. Contact oxidation under humid condition | 1. Replace with compatible 3TY7561 |
| 2. Loose wiring | 2. Retighten terminal screws | |
| Contactor pulls in but NC fails to open | 1. Loose & fallen snap clip | 1. Reinstall and lock into position |
| 2. Mechanical blockage inside block | 2. Replace block; inspect deformed contactor shaft | |
| Contact arcing & burnout | 1. Exceeding AC-15 rated current | 1. Add intermediate relay for load expansion |
| 2. High inductive surge from load | 2. Fit RC snubber circuit for surge suppression | |
| Abnormal overheating | 1. High contact resistance at terminals | 1. Clean terminals & re-terminate |
| 2. Excessive ambient temperature | 2. Improve ventilation or use high-temperature variant |
- Quick Selection Mnemonic
4001 = NC, 4010 = NO; front snap exclusively for 3TF;<br>Obsolete → swap to 3TY; upgrade to 3RT with 3RH;<br>Only for control circuit, never main power, excellent for safety interlock!
- HS Code & Air Shipment Compliance
HS Code: 85365000 (Electrical switching apparatus for circuit protection)
Air Transport Classification: Non-dangerous goods, purely mechanical contacts with no lithium battery/supercapacitor, compliant with IATA DGR
CE Certification: Complies with Low Voltage Directive 2014/35/EU; Certificate of Conformity available upon request
Application Scope of 3TX4001-2A (Front-mounted 1NC Auxiliary Contact)
Product Feature: Snap-on external 1NC contact for 3TF3/3TF4 contactors, rated AC-15, dedicated for secondary control circuit only, NOT permitted in main power circuit.
- Standard Common Applications
1.1 Motor Start-Stop Control (Fans, Water Pumps, Air Compressors)
- Passive running status feedback
Contactor coil energizes → NC opens, sends closing/running feedback signal to PLC DI module; coil de-energizes → NC resets closed to transmit stop signal.
Typical usage: Chilled water pumps, cooling blowers, circulation pumps, central air-conditioning units.
- Electrical interlock protection
Mutual NC interlock between two contactors (forward/reverse or star-delta) to avoid simultaneous closing and phase short-circuit.
Example: Star-delta motor starter interlock between star & delta contactors.
1.2 Machine Tool & Automation Equipment (Lathe, Conveyor, Injection Molding Machine)
- Cabinet door interlock: NC of main contactor wired into safety loop; if contactor is welded closed, NC stays open to block equipment restart.
- Conveyor sequential interlock: Interlock between upstream & downstream conveyor contactors to prevent mechanical collision from misoperation.
- Fault alarm: Normally closed NC in series with fault indicator lamp; lamp lights at standby/shutdown and goes off when contactor pulls in.
1.3 HVAC Industry (Central AC, Fresh Air Unit, Smoke Exhaust Fan)
- BA system signal collection: Fan contactor NC feeds start/stop remote data to building management controller.
- Fire smoke exhaust interlock: NC links with fire damper; damper shutdown cuts fan control circuit.
1.4 Water Treatment Equipment (Dosing Pump, Sewage Pump, Aeration Blower)
- Pump overload linkage: Thermal relay trip resets contactor, closed NC triggers audible-visual fault alarm.
- Duty/standby pump auto-switch: Main pump fault closes NC to activate backup pump automatically.
1.5 LV Power Distribution Panels
- Capacitor compensation cabinet: NC of switching contactor feeds capacitor switching status to reactive power regulator.
- ATS cabinet: Electrical interlock between normal & backup supply contactors to eliminate cross-source short-circuit risk.
1.6 Hoisting & Elevator Auxiliary Control
Brake contactor NC of overhead crane feeds brake open/closed feedback; also for cooling fan contactor status monitoring on elevators.
- Safety Circuit Exclusive Usage (Positively Driven Contact per Machinery Safety Standards)
- Emergency stop monitoring: Detects welded contactor fault; mechanically stuck contactor keeps NC open to lock control power off.
- Safety guard circuit: Equipment door opening de-energizes main contactor, closed NC locks startup circuit.
- Low-power Indicator & Small Relay Driving
- Standby pilot lamp: NC closed to light indicator at idle; NC opens to turn lamp off during equipment operation.
- Mini intermediate relay drive: NC switching controls relay coil to amplify load capacity.
- Prohibited Application List
- ❌ Never connect to 220V/380V main power loop; AC-15 rating only for control loads, cannot directly drive motor/heater high-power loads.
- ❌ Avoid >55℃, strong acid/alkali corrosion & unprotected open-air cabinets (accelerates contact oxidation & bad conduction).
- ❌ Unsuitable for heavy DC loads (no DC-13 rating; DC breaking easily causes arc burnout).
- ❌ Ban over 15 switching cycles per minute (fast mechanical wear; replace with solid-state relay).
