MLFB Order Code Breakdown
3RW 44 43 6 B C 4 4
- 3RW: SIRIUS soft starter product series
- 44: High-performance built-in bypass 3-phase fully controlled avviatore morbido (independent thyristor regulation per phase, integrated bypass contactor as standard)
- 43: Codice taglia, corrente nominale 203 A a 40 °C for standard loads
- 6: Control circuit terminal type = screw terminals; main circuit connected via copper busbars
- B: Integrated bypass contactor (2/3-phase bypass for zero loss during steady-state operation)
- C: Independent 3-phase thyristor control (full 3-phase control to balance 3-phase currents)
- 4: Control supply voltage Us = AC 230 V
- 4: Main circuit operating voltage Ue = AC 200~460 V
- Parametri elettrici principali (40 °C, Classe 10 Standard Load)
| Articolo | Valore del parametro |
| Rated current for standard wiring (motor directly connected to soft starter) | 203 UN |
| Matched motor power at 400 V | 110 kW |
| Rated current for inside-delta connection (motor windings split into two branches) | 352 UN |
| Matched motor power at 400 V for inside-delta wiring | 200 kW |
| Intervallo di tensione del circuito principale | AC 200~460 V (50/60 Hz) |
| Control supply | AC 230 V ±10% |
| Phase control mode | Anti-parallel thyristors per phase with independent regulation |
| Standard functions | Integrated bypass contactor to bypass thyristors during running |
| Standard overload trip class | Classe 10; Classe 10/20/30 configurable manually |
| Funzioni di protezione | Phase loss, phase unbalance, sovraccarico del motore, surriscaldamento, thyristor short-circuit, start timeout, earth fault detection |
| Communication expansion | Profibus DP compatible (requires 3RW4900-0KC00 communication module) |
| Peso | ca. 11.2 kg |
| Country of origin | Germania |
III. Carica corrispondenza & Selection Limits
- Carichi applicabili
Pompe dell'acqua, tifosi, trasportatori a nastro, compressori d'aria, refrigeratori, centrifugal equipment (fixed speed, only smooth start/stop required)
- Derating Reference for Heavy-Duty Operation (40 °C)
Classe 20 servizio pesante (frequent starts, elevata coppia di spunto): permissible current 170 UN, matched motor 90 kW
Classe 30 extra heavy duty (mulini a sfere, frantoi): permissible current 145 UN, matched motor 75 kW
- Prohibited Operating Conditions
Continuous speed regulation, frequent forward/reverse switching, high-frequency jogging (≥30 times per hour)
- Hardware Structure & Descrizione del cablaggio
- Circuito principale: Copper busbar terminals; L1/L2/L3 line side input, T1/T2/T3 motor side output; supports standard wiring and inside-delta wiring
- Circuito di controllo: Screw terminals for start/stop signals, fault outputs, reset, external thermistor input
- Pannello operatore: Built-in LCD display for setting start ramp, initial voltage, soft stop, current limit and protection thresholds
- Installazione: Vertical wall mounting; minimum 150 mm top/bottom clearance for heat dissipation; ambient temperature 0~40 °C (derate for temperatures above 40 °C)
- Ciclo di vita del prodotto & Modelli sostitutivi
- Stato: 3RW44 series discontinued (PLM: PM490 end-of-support phase); original manufacturer stops mass production, only stock spare parts available
- Direct OEM Replacement Model (Recommended for New Projects)
3RW5543-6HA14 (new-generation 3RW55 series, same 203 Una corrente nominale, 230 V control supply, 200-460 V main voltage, terminali a vite, integrated bypass)
- Differences Between Old & Nuovi modelli
Smaller footprint, consumo energetico inferiore, native Modbus RTU and optimized protection logic for 3RW55
Different mounting cutout dimensions; copper busbars and mounting brackets need modification during cabinet retrofit
- Recommended Matching Protection Devices
- Main Circuit Short-Circuit Protection: Moulded case circuit breaker matched to 110 kW motor circuit
- Specialized Thyristor Protection: aM/gR ultra-fast fuse 500 V 315 UN (mandatory upstream of soft starter, no thyristor short-circuit protection without it)
- Additional Motor Protection: External PTC thermistor connectable to control terminals for winding overtrip protection
VII. Typical Troubleshooting Matrix
| Sintomo di guasto | Causa ultima | Soluzione |
| Overheating alarm during startup | Blocked cooling air duct / ambient temp above 40 °C / long-duration heavy-load startup | Clean dust, improve cabinet ventilation, upgrade to higher-rated soft starter |
| Phase loss alarm | Perdita di potenza monofase, loose busbar connection, broken motor winding | Tighten wiring, measure 3-phase input voltage and motor winding resistance |
| Unrestricted starting current, direct full voltage output | Broken-down thyristors, welded bypass contactor contacts | Disconnect power supply to test thyristors; replace bypass contact module |
| Startup timeout trip | Too low initial voltage, seized mechanical load, insufficient ramp time | Increase initial voltage, inspect mechanical load, extend start ramp time |
VIII. Vantaggi principali
- Independent 3-phase voltage regulation; eliminates 3-phase current unbalance common in 2-phase soft starters, extending motor bearing service life
- Integrated bypass eliminates thyristor power loss during steady operation, delivering over 98% energy saving vs non-bypass models
- Supports soft stop and pump stop water hammer suppression, ideal for water supply, drainage and HVAC systems
- Comprehensive integrated motor protection, eliminating the need for separate thermal overload relays
Full Dimension Specifications of Siemens 3RW4443-6BC44
- Overall Equipment Dimensions (L × A × P, Unità: mm)
210 (Larghezza) × 230 (Altezza) × 298 (Profondità)
- Mounting Cutout & Fixing Dimensions
- Horizontal center distance between mounting holes: 167 mm
- Vertical center distance between mounting holes: 190 mm
- Fastener specification: M8 bolt, coppia di serraggio 15 N·m
- Cabinet panel cutout minimum reserved width ≥210 mm, height ≥230 mm
III. Mandatory Minimum Cabinet Clearance for Heat Dissipation (Vertical Wall Mount)
Top clearance: ≥100 mm
Bottom clearance: ≥75 mm
Side clearance (multiple units side-by-side): ≥5 mm
Equipment rear surface to cabinet backplate: direct contact permitted
- Outer Carton Dimensions (Magazzinaggio & Logistics Reference)
348 × 433 × 394 mm, peso netto 11.22 kg
- Note supplementari
- Classe di protezione: IP00; for cabinet installation only
- All 3RW4443 variants (-6BC34/-6BC44/-2BC45) share identical overall dimensions; differences only in control terminals and supply voltage
- Replacement model 3RW5543-6HA14 has a smaller footprint; recalculate cabinet cutout size for retrofits
Complete List & Function Definition of Control Terminals – Siemens 3RW4443-6BC44
This model is equipped with screw-type control terminals, categorized into five groups: controllare l'alimentazione, ingressi digitali, motor PTC temperature sensing, uscite relè programmabili, general fault relay.
- Control Power Supply Terminals (Unit Main Supply)
- A1, A2
Funzione: Main control power supply for soft starter
Model rating: AC 230 V ±10%, 50/60 Hz
Wiring rule: A1 live line L, A2 neutral line N
- PE
Control circuit protective earth terminal; connect to cabinet earth busbar
- L+, l-
Built-in internal DC24 V auxiliary supply for passive digital input switches; external 24 V power supply not required
L+ = DC24 V positive pole; L= DC24 V negative pole (common ground)
- 4 Programmable Digital Input Terminals IN1 / IN2 / IN3 / IN4
Logica: Connect one end of switch to L+, the other end to corresponding INx to trigger assigned function; all functions configurable via panel parameters
Factory Default Allocation
IN1: Motor start (Parameter Group 1 rotazione in avanti)
IN2: Unassigned
IN3: Unassigned
IN4: Fault trip reset
All Customizable Functions
Local manual mode, emergency start, low-speed creep, fast emergency stop, fault reset, 3 groups of forward/reverse motor parameter switching
III. Motor Winding Temperature Sensing Terminals T1, T2
For external motor PTC thermistor connection (motor overheat protection)
Soft starter trips automatically when winding temperature exceeds threshold
Short-circuit T1 and T2 if no PTC fitted to disable thermal protection
- 3 Independent Programmable Relay Outputs (Passive dry contacts, AC250 V / 5 UN)
Each pair consists of normally-open contacts with fully assignable functions via parameter menu
- 13, 14 Produzione 1
Predefinito: Motor running signal (closes after startup completion and bypass contactor pull-in)
- 23, 24 Produzione 2
Predefinito: Unassigned; configurable for bypass status, startup-in-progress, pre-alarm, DC braking, ecc.
- 33, 34 Produzione 3
Predefinito: Unassigned; customizable for all types of equipment status signals
- General Fault Relay Terminals 95, 96, 98 (Global Fault Alarm)
3-pole changeover contact for unified fault signaling, widely used in safety circuits
95: Common terminal COM
95-96: Normalmente chiuso (NC): conductive when unit healthy; opens upon fault trip
95-98: Normalmente aperto (NO): closes when fault occurs, for fault indicator light / alarm horn wiring
Terminal Summary Table
| Terminal Group | Terminal Number | Core Purpose |
| Controllare l'alimentazione | A1, A2 | AC230 V control voltage input |
| Terra protettiva | PE | Control circuit grounding |
| Integrato 24 V Supply | L+, l- | DC24 V power for digital inputs (positive / ground) |
| Ingressi digitali | IN1, IN2, IN3, IN4 | Start/stop, reset, parameter switchover, manual mode etc. |
| PTC Temperature Sensing | T1, T2 | Motor winding overheat thermistor interface |
| Uscita relè 1 | 13, 14 | Motor running status (normalmente aperto) |
| Uscita relè 2 | 23, 24 | Customizable equipment status (normalmente aperto) |
| Uscita relè 3 | 33, 34 | Customizable equipment status (normalmente aperto) |
| Fault Changeover Contact | 95, 96, 98 | Global fault alarm (COM + NC + NO) |
Supplementary Wiring Guidelines
- Tightening torque for control wires: 1.2~1.5 N·m; wire cross-section 0.75~1.5 mm² copper conductors
- Digital inputs are passive contact type; power solely from internal L+/Lwithout external PLC 24 fornitura V
- Series the normally closed 95/96 contacts in safety circuit to cut upstream contactor power on fault
- Profibus communication requires separate 3RW4900-0KC00 module with dedicated port (not part of front control terminals)
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