Schneider LTMR27MFM Motor Management Controller

Application Fields of Schneider LTMR27MFM (TeSys T)

Current rating: 1.35～27A intelligent management controller for 3-phase asynchronous motors, equipped with Modbus-RTU communication. Widely deployed inside MCC cabinets for integrated motor protection, current monitoring and remote data transmission.

Scomposizione del codice modello

LTMR27MFM

LTMR: TeSys T motor management controller base unit

27: Current measuring range 1.35～27 A (integrated current transformers)

M: Communication interface → Modbus RS485

FM: Control supply 100～240 VAC (AC)

Cross reference within series: LTMR27EFM = Ethernet; LTMR27CFM = CANopen

2. Main Electrical Specifications

3. Built-in Protection Functions

✅ Thermal overload protection (thermal model)

✅ Phase loss & 3-phase current unbalance protection

✅ Locked rotor protection, protezione da avviamento prolungato

✅ Underload protection (dry-running/belt breakage monitoring)

✅ Earth fault protection (internal or external zero-sequence CT)

✅ Support for PTC motor thermistor input

✅ Fault logging, trip history, contatore delle ore di funzionamento

4. Measurement Capability (Voltaggio & power measurement with LTME extension module)

Base unit measurement: 3-phase current, average current, unbalance current, earth fault current;

When fitted with LTME extension module: additional 3-phase voltage, potenza attiva/reattiva, fattore di potenza, energy metering.

5. Commissioning Software

Configuration via SoMove software (TeSys T DTM). Connect PC directly via front RJ45 HMI port for parameter setting, fault reading and real-time monitoring.

Optional local display panel: LTMCU / LTMCUF.

6. Lifecycle Notice

The full LTMR TeSys T series is undergoing phase-out (EOL).

Official order cutoff date: 30 Sep 2026; Technical support ends: 31 Jan 2027

Sostituzione di nuova generazione: TeSys Tera

Unità principale: LTMTMFM (ModBus, 100~240 VCA/CC)

Match current sensor:

2.5～25A → LTMTCTV25UT (closest match for original 1.35~27A application)

⚠️ Wiring layout and Modbus register mapping are not fully compatible between old and new series. On-site retrofit requires program re-commissioning.

7. Applicazione tipica

MCC Motor Control Centers, pompe dell'acqua, tifosi, compressori, trasportatori; projects in water treatment, HVAC, metallurgy and cement industries.

8. Quick Distinction of Similar Models

LTMR27MFM：1.35~27A, ModBus, 100~240VAC

LTMR100MFM：5~100A, ModBus, 100~240VAC

LTMR27EFM：1.35~27A, Ethernet/IP

Main Industry Segments

1. Municipal Water Supply & Wastewater Treatment (Applicazione più comune)

✅ Municipal wastewater plants, waterworks, pumping stations

✅ Typical loads: pompe sommergibili, centrifugal pumps, pompe di recupero fanghi, ventilatori di aerazione, raschiatori

Key requirements satisfied: underload protection (dry-run prevention), earth fault protection, remote fault alarming, energy monitoring.

2. HVAC, Edifici commerciali & Costruzione di sistemi elettromeccanici

✅ Shopping malls, ospedali, centri dati, industrial park chiller plants

✅ Typical loads: chilled water pumps, pompe dell'acqua di raffreddamento, ventilatori delle torri di raffreddamento, ventilatori di scarico, AHU fans

Vantaggio: sovraccarico termico & protezione del rotore bloccato; Modbus connection to building BA system for current data and fault signals.

3. Cemento, Materiali da costruzione & Aggregate Mining Production Lines

✅ Belt conveyors, elevatori a tazze, auxiliary drives for roller presses, dust extraction fans, silo discharge equipment

✅ Targeted protection: protezione del rotore bloccato, protezione da avviamento prolungato, phase unbalance protection to avoid motor burnout caused by mechanical jamming.

4. Chimico & Industria farmaceutica

✅ Circulation pumps, agitator motors, auxiliary air compressor motors, dust fans

✅ Supports PTC thermistor connection for motor winding temperature monitoring; fast tripping upon phase loss and earth faults to meet industrial safety standards.

5. Cibo & Bevanda, Packaging Production Lines

✅ Conveyor motors, soffiatori, wash pumps, packaging machine drives

Accurate underload monitoring to detect material shortage or belt detachment; fault history facilitates production maintenance.

6. Transito ferroviario & Tunnel Electromechanical Systems

✅ Tunnel jet fans, drainage pumps, smoke exhaust fans

Reliable protection for fire service motors; data upload to tunnel PLC control system.

7. Power Plant Auxiliary Equipment

✅ Circulating water pumps, ventilation fans, ash handling conveyors; standard component inside power station MCC rooms.

8. Porta & Magazzino logistico

✅ Conveyors, stacker auxiliary drives, dust extraction fans, hydraulic station oil pumps

Matching Motor Power Reference (380V 3-phase motors)

LTMR27MFM measuring range 1.35～27A

Suitable motor power range: 0.75kW～13kW three-phase asynchronous motor.

Scenari applicativi non consigliati

1. Motors above 13kW (select LTMR100 series instead)
2. Equipment with frequent forward/reverse rotation and heavy impulse jogging operation (thermal model parameters require special evaluation)
3. Explosion-proof enclosures without sufficient heat dissipation (ambient temperature must remain ≤60℃)

Selection Advantages Matched to Operating Conditions

Integrated current transformers, no external CT required, simplifies cabinet wiring;

Modbus RS485 interface, seamless connection with Schneider PLC (Modicon M241/M251/M340 etc.);

Comprehensive protection suite: sovraccarico, rotore bloccato, perdita di fase, squilibrio attuale, sottocarico, guasto a terra, PTC temperature monitoring;

Fault history recording & running hour statistics, compliant with smart factory and energy management projects.

Operating Principle of Locked Rotor Protection on Schneider TeSys T LTMR27MFM

The LTMR27MFM implements locked rotor protection via real-time 3-phase current sampling + time threshold judgment, split into two independent configurable modes: Locked Rotor Protection during Start-up and Locked Rotor Protection in Running State.

1. Hardware Foundation

The LTMR27MFM integrates built-in 3-phase current transformers to continuously sample stator current at high speed. The internal MCU calculates in real time:

1. RMS value of three-phase currents
2. Ratio between instantaneous current and rated operating current
3. Duration of over-limit condition

No additional external sensors required; diagnosis relies purely on current signature analysis.

2. Two Locked Rotor Protection Modes (Independently configured in SoMove)

Modalità 1: Locked Rotor Protection during Motor Start-up

Application scenario: Motor cannot accelerate due to mechanical jamming at startup

1. Judgment window: Controller identifies startup sequence (current surge, motor at standstill before acceleration)
2. Logica:

If start-up current ＞ Locked Rotor Start Threshold, and duration ≥ Locked Rotor Start Delay → Trip command triggered

3. Adjustable parameters (Quindi Muoviti):

Locked rotor start current: typical range 1.5～8× motor rated current Ie (default 5Ie)

Locked rotor start delay: typical range 0.5～10 s

Scopo: Prevent winding burnout caused by prolonged high current when motor is blocked on startup; distinguish permanent stall from normal short-duration starting inrush current.

Modalità 2: Locked Rotor Protection during Steady-State Operation

Application scenario: Mechanical blockage occurs after motor reaches rated speed (belt jamming, pump impeller stuck, foreign object entrapment)

1. Judgment window: Controller confirms motor completes acceleration and enters stable operation
2. Logica:

If operating current ＞ Running Locked Rotor Threshold, and duration ≥ Running Locked Rotor Delay → Trip command triggered

3. Parameter characteristics:

Running locked rotor threshold is generally set lower than start-up threshold (typically 1.8～4 Ie), with shorter delay for rapid fault isolation.

3. Full Internal Decision Workflow
4. LTMR continuously samples three-phase currents and monitors current variation trends;
5. Automatically distinguishes three operating states: Standstill → Start-up → Steady Run;
6. Activates corresponding locked rotor threshold rules according to operating state;
7. Starts timing once current exceeds set threshold continuously;
8. When timing reaches configured delay:

✅ Internal protection sequence activated;

✅ Fault relay contact changes state;

✅ Disconnects contactor control circuit;

✅ Stores fault code BLR (Blocked Rotor) locally;

✅ Uploads locked rotor fault information to upper-level PLC via Modbus.

⚠️ Critical Distinction: Locked Rotor Protection ≠ Thermal Overload Protection

Protezione da sovraccarico termico: Based on motor thermal accumulation model, trips for sustained mild overload; slow response characteristic.

Locked Rotor Protection: Fast acting definite-time protection against severe instantaneous overcurrent caused by mechanical stall, compensating the slow response of thermal protection.

4. Key Commissioning Guidelines
5. Motor rated current Ie must be entered accurately

All locked rotor thresholds are calculated as multiples of Ie. Incorrect setting leads to protection failure.

2. Tuning principles for delay

Tifosi & centrifugal pumps: Longer natural startup time → extend start-up locked rotor delay to avoid nuisance tripping.

Trasportatori & frantoi: High risk of mechanical jamming → minimize running locked rotor delay for fast protection.

3. Coordinamento della protezione

Locked rotor protection can be enabled together with phase loss, sbilanciare, underload and PTC temperature protection for multi-layer safety.

4. Common setting pitfall

Do not set locked rotor threshold higher than the actual motor starting inrush current; otherwise protection will fail to respond during blocked startup.

5. Fault Identification After Trip

With local display panel LTMCU: Fault code BLR shown on screen

SoMove fault log: Recorded as Blocked rotor

Corresponding dedicated Modbus fault register bit for HMI/PLC alarming.

6. Limitazioni funzionali

Locked rotor protection relies solely on stator current signature. Rare edge case limitation:

If mechanical jamming occurs with light load and current does not rise above threshold, stall cannot be detected. For such conditions, implement redundant monitoring via underload protection or vibration sensors.