Motor Protection Relay

MPU 32 Series

Added to List
  • Protects through starting, running, and cooling cycles
  • View measured values and event records, reset trips, and access setpoints remotely 
  • Ten year warranty


The Liitelfuse MPU-32 Motor Protection Unit provides current and temperature-based protection, metering, and data logging for three-phase low-voltage medium-horsepower induction motors. 

This relay is ideal for retrofitting and upgrading obsolete or aging motor protection using existing CTs. See the PMA Family of Panel Mount Adapter Kits to replace common obsolete relays.

The Current Input Module (MPU-CIM) is the interface between the MPU-32 relay and the 5-A-secondary, 1-A-secondary, and sensitive current transformers. The MPU-CIM is ordered separately.

Overload - IEEE # 49, 51

Extends motor life and prevents insulation failures and fires.

Dynamic thermal model

Provides protection through starting, running, and cooling cycles.

Earth fault – IEEE # 50G/N, 51G/N

Prevents catastrophic failures and fires.

Current unbalance/Phase loss/Phase reverse – IEEE # 46

Prevents overheating due to unbalanced phases.

RTD temperature – IEEE # 38, 49

MPS-RTD module for high-ambient or loss-of-ventilation protection.

Phase loss/Phase reverse (current) – IEEE # 46

Detects unhealthy supply conditions.

Overcurrent – IEEE # 50, 51

Prevents catastrophic failures and fires; extends motor life.


Prevents motor damage by detecting mechanical jams or excessive loading.

Undercurrent – IEEE # 37

Detects low level or no-load conditions.

PTC overtemperature – IEEE # 49

Overtemperature (PTC) protection for high-ambient or loss-of-ventilation detection.

Starts per hour – IEEE # 66

Limits the motor starts per hour to prevent overheating.

Differential – IEEE # 87

Optional MPS-DIF module for sensitive winding-fault protection.

Reduced overcurrent mode

Minimises arc-flash hazards during maintenance.


View measured and calculated parameters with on-board display.


Separate current input module to reduce risk of open-CT hazard and for convenient installation.

Analog output

Provides means for metering selectable parameters.

Data logging

On-board 100-event recorder for data logging.

Conformal coating

Internal circuits are conformally coated to protect against corrosion and moisture.

Data Sheets and Manuals

MPU-32 Data Sheet MPU-32 ManualMPU-CIM MechanicalMPU-CIM WiringMPU-32 Ethernet IP ManualMPU-32 and FPU-32 Modbus TCP ManualMPU-32 and FPU-32 TIA 485 ManualMPU-32 DeviceNet ManualTN MP18 Replacing MPU 16 with MPU-32

CAD Drawings and Models

MPU-32 CAD DrawingMPU-32 Wiring DiagramMPU-32 Wiring Diagram with EFCT

Software and Manuals

SE-Comm-RS v4,2 SoftwareMPU-32 FPU-32 Firmware Update Instructions

Protective Functions (IEEE Device Numbers)

Overload (49, 51), RTD temperature (38, 49), Phase reverse (current) (46), Overcurrent (50, 51), Jam, Earth fault (50G/N, 51G/N), PTC overtemperature (49), Unbalance (current) (46), Starts per hour (66), Differential (87), Phase loss (current) (46), Undercurrent (37)

Input Voltage

65-265 Vac, 25 VA; 80-275 Vdc, 25 W

Power-Up Time

800 ms at 120 Vac

Ride-Through Time

100 ms minimum

24-Vdc Source

100 mA maximum

AC Measurements

True RMS and DFT, Peak, 16 samples/cycle, and positive and negative sequence of fundamental


50, 60 Hz or ASD

Output Contacts

Three Form C programmables


TIA-232 (standard); TIA-485, DeviceNet™, Ethernet (optional)

Analog Output

4-20 mA, programmable


10 years

Mounting (Control Unit)

Panel (standard), Surface (with MPU-32-SMK converter kit)

Mounting (Current Input Module)

DIN, Surface



Makes Perfect Sense

Exceptional choice, exclusive ranges, high stock levels, excellent value and a passion for expert personal service. Why would you look anywhere else for your electrical, lighting, air conditioning and refrigeration needs?