GEMotor Protection System Integrated process, control, and protection for low voltage motors

featured protection for low voltage AC motors

• Advanced automation capabilities providing customized 

protection and integrated automation control

• Cost effective solution - Low cost modular design

• Small footprint and compact design - With or without 

display, fits into standard MCC buckets

• Preconfigured logic for all standard motor starter types, 

EnerVistaTM compatible

• Integrated motor control pushbuttons

• Remote monitoring via serial communications, Modbus RTU

• Easy installation and integration - Panel mount option

• Reduced number of devices - Replaces bi-metal overload 

elements, integrates timers, relays, meters, switches, 

indicators

• Motor protection and management system for low voltage 

AC motors

• Specifically designed for Motor Control Centre applications

• Motor operational parameters and historical data

• Process data

• Phase and ground current, power, energy, voltage

• Status of relay inputs

• Trip record and pre-trip values 

• Motor statistical information

Monitoring and Metering

User Interface

Protection and Control

• Motor Thermal Model

• Single phase / Current unbalance 

• Contactor failure 

• Locked/stalled rotor 

• Ground fault 

• Undervoltage, Overvoltage

• Overtemperature

• Acceleration Trip 

• Thermistor Protection 

• Starts per Hour / Time Between Starts 

• Undercurrent and underpower

• Configurable motor start controller

• Undervoltage auto restart 

• 40 Character LCD display

• Front Panel control push buttons and programming keypad

• 11 Motor and Relay Status LED’s

• RS485 ModBus™ , 1200 - 19,200 bps

Motor Protection System

Integrated process, control, and 

protection for low voltage motors

Features

Applications

K

EnerVistaTM Software

• State of the art software for configuration and 

commissioning GE Multilin products

• Document and software archiving toolset to ensure 

reference material and device utilities are up-to-date

• EnerVistaTM Integrator providing easy integration of data 

in the MM2 into new or existing monitoring and control 

systems

Protection and Control

The MM2 is a digital motor protection 

system designed to protect and manage 

low voltage motors and driven equipment. 

It contains a full range of selectively 

enabled, self contained protection and 

control elements as detailed in the 

Functional Block Diagram and Features 

table.

Thermal Overload

An overload trip occurs when the 

thermal capacity value equals 100%. 

Thermal capacity used is calculated from 

accumulated I2t value and chosen 

overload curves. True RMS current sensing 

ensures correct response to the heating 

effect of harmonics. One of 12 different I2t 

time overcurrent overload curves may be 

selected from eight standard curves and 

four NEMA compatible curves.

Phase Unbalance

The MM2 monitors the percentage 

unbalance in the motor phase currents. If 

a phase current unbalance of greater than 

15% exists for more than five seconds an 

alarm is generated. If a phase current 

unbalance of greater than 30% exists for 

more than five seconds a single phase trip 

occurs.

Locked/Stalled Rotor

To help prevent damage to mechanical 

equipment such as pumps or fans, the 

MM2 will trip when the running current 

exceeds the stalled rotor trip level after the 

programmed time delay. This feature may 

be set to ‘OFF’ if desired, and it is disabled 

during motor starting.

Ground Fault

The ground fault level is measured as a 

percentage of the CT primary. Ground 

overcurrent can be detected either from 

the residual connection of the phase 

CTs or from a zero sequence CT. A delay 

time is set to prevent false alarms from 

momentary surges. Both a ground fault 

alarm and trip are provided. The alarm 

can be set below the trip level to provide 

an early warning of insulation breakdown.

Overtemperature

An input from motor winding thermistors 

is available. The MM2 can accept both 

positive temperature coefficient (PTC) and 

negative temperature coefficient (NTC) 

sensors. A thermistor level can be selected 

for both alarm and trip.

Cooling Time

After an overload trip, the thermal 

capacity value decreases exponentially 

to model the motor cooling characteristic. 

An overload trip can be reset when the 

thermal capacity value decreases to 15%. 

A stopped motor cooling time can be set to 

determine how long it takes for a stopped 

motor to reach steady state ambient 

temperature from its maximum allowable 

temperature.

Undercurrent/Underpower

Both undercurrent and underpower alarms 

and trips are provided with time delays. 

Protection against failed shear pin or loss 

of pump flow, which may result in only a 

small change in current, is provided by the 

underpower alarm.

Undervoltage 

For voltage sensitive loads, a drop in 

voltage increases the drawn current, 

which may cause overheating in the 

motor. The undervoltage protection 

feature can be used to either cause a trip