GE MM2 Motor Manager Complete Guide

When the motor suddenly stops running, there is no record of any tripping. The external stop signal (terminal 51) is instantly powered off or the Process Stop input is activated. ① Check if there is any interruption in the Stop input circuit; ② View A2: Pause of STOP in Status; ③ If it is a Field STOP issue, check whether the Field STOP setting in S3 is UNLATCHED or LATCHED.

The contactor is engaged but the motor does not rotate, and there is no alarm. The main contact of the contactor is burned or the motor power supply is out of phase. MM2 only monitors control loop feedback and does not monitor main loop current. Need to check the three-phase current values in A1: DATA. If a certain phase is 0, check the CT wiring or the main contact of the contactor.

Other important checklists (see Appendix B):

Grounding: Terminal 13 (safety ground) and 14 (filtering ground) must be connected to the grounding busbar with a thick wire.

CT secondary side grounding: All external CT secondary windings should be grounded, but note that terminal 11 of the 50:0.025 CT is already internally grounded and cannot be externally grounded again.

Thermistor: Use shielded cables with a resistance value ranging from 100 to 30000 Ω. If a thermistor is not used, THERMOSTOR ALARM and TRIP must be set to DISABLE in S1, otherwise false alarms will occur.

Contactor status feedback: Feedback must be received within 1 second after closing the contactor, otherwise MM2 will disconnect the contactor to prevent the control circuit from opening.

Debugging and upgrading using MM2PC software

MM2PC is a free Windows software provided by GE Multilin, which greatly simplifies parameter settings, actual value monitoring, and firmware upgrade work. Minimum requirement: Windows 3.1/95/98, 6MB hard disk space (modern system compatibility can be resolved through virtual machines).

Key operations:

Connection and communication configuration: Connect MM2 through RS232/RS485 converter. Set the correct COM port, baud rate (default 9600), data bit 8, stop bit 1, and verify NONE in the software. After successful communication, the status bar in the lower right corner displays "Program is now talking to Multilin device

Save/Load Setpoint File: Use File>Save As to save the current configuration as MM2 file. This is very useful for batch configuring motor cabinets of the same specifications. After File>Open, download to another MM2 through Send Info To Relay.

Firmware upgrade: Be sure to save the original set points before upgrading. Select Communications>Upgrade Firmware and choose firmware files starting with "71". After upgrading, it is necessary to reload the set points.

Trending chart: It can real-time draw parameters such as Ia, Ib, Ic, Ignd, heat capacity, voltage, etc., to help analyze the motor starting process or abnormal fluctuations.

Users can define memory mapping: Write the register addresses that need to be read continuously in addresses 1280H~12F7H (such as 0031H for A-phase current and 0023H for driving state), and then quickly batch read through 0100H~0177H to improve communication efficiency.

For special settings of chassis installation (without display screen) models: This type of MM2 defaults to 9600 baud, no parity, and does not support automatic baud rate linking. It is necessary to establish communication with this setting first, and then change the baud rate and checksum one by one through Modbus function codes or software. Please refer to section 9.5 of the manual for specific steps.

Application Example: Wiring and Setting of Reverse Starter

Taking the Full Voltage Reversing starter as an example, the specific configuration and hardware connection of MM2 will be explained.

Set point:

S1: STARTER TYPE = FV REVERSING

S1: Transfer TIME=Assuming a delay of 5 seconds (from forward to reverse)

S3: PROGRAMMABLE INPUTS: An input can be configured as INTERLOCK COUNTER, etc. (not mandatory)

S4: AUX RELAY 1/2 can be allocated on demand

Key points of hardware wiring:

The forward contactor coil is controlled by the Contactor A relay (terminal 34/35) of MM2.

The reverse contactor coil is controlled by the Contactor B relay (terminals 32/33).

Connect the auxiliary normally open contact of contactor A to terminal 55 (Contactor A Status N.O.)

Connect the auxiliary normally open contact of contactor B to terminal 56 (Contactor B Status N.O.)

The stop button is connected in series to terminal 51 (Stop input) circuit and must be normally closed.

Connect the Start A button to terminal 52 and jog it; Connect the start B button to terminal 53 (Start B) and jog it.

Running logic:

After receiving the Start A command, MM2 closes Contactor A and the motor rotates forward. If Start B is received when the motor is already rotating forward, MM2 first disconnects Contactor A, waits for Transfer Time (e.g. 5 seconds), then closes Contactor B, and the motor rotates in reverse.

If feedback is not received within 1 second after the output relay is closed, an OPEN CON CIRCUIT alarm will be generated and the contactor will be disconnected.

Stop command (via terminal 51 or Stop button) or any protective trip, immediately disconnect all contactors.