GE Power Management
MM2 Motor Manager 2 9-25
9 STARTER TYPES 9.8 AUTOTRANSFORMER CLOSED TRANSITION STARTER
9
The CONTACTOR SEQUENCE setpoint appears when the Autotransformer Closed Transition starter type
has been selected. The 1S-2S value means that the 1S contactor will close ahead of the 2S contactor
as per some manufacturers wiring practices. The 2S-1S value means that the 2S contactor will close
ahead of the 1S contactor as this is another common wiring practice.
The CHANGE OVER TIME setpoint appears only if the Autotransformer Open or Closed Transition
starter types have been selected. For the Autotransformer starter type, this is the time delay from the
closure of Contactor A output relay until the opening of Contactor A output relay.
The STARTS PER HOUR setpoint only if the Autotransformer starter type has been selected. This set-
point limits the number of starts per hour to prevent overheating of the autotransformer windings.
9.8.2 MM2 SEQUENCES
START (CONTACTOR SEQUENCE set to 1S-2S) sequence:
1. Start command received by the MM2 (serial, switch input or faceplate).
2. Close and maintain Contactor A output relay – close 1S contactor.
3. Wait 20 ms, close and maintain Aux. 1 relay – power is applied to the autotransformer.
4. Wait for the time set in the CHANGE OVER TIME setpoint.
5. Open contactor A output relay and wait 20 ms.
6. Close and maintain Contactor B output relay.
7. Wait 20 ms.
8. Open Aux. 1 output relay.
START (CONTACTOR SEQUENCE set to 2S-1S) sequence:
1. Start command received by the MM2 (serial, switch input or faceplate).
2. Close and maintain Aux. 1 output relay – power is applied to the autotransformer.
3. Wait 20 ms, close and maintain Contactor A relay – close the 1S contactor.
4. Wait for the time set in the CHANGE OVER TIME setpoint.
5. Open contactor A output relay and wait 20 ms.
6. Close and maintain Contactor B output relay.
7. Wait 20 ms.
8. Open Aux. 1 output relay.
STOP/TRIP sequence:
1. Stop command received by the MM2 or a trip occurs.
2. Open Contactor B output relay.
If feedback is not received by the Contactor A, B or auxiliary relay Status N.O. inputs within one sec-
ond of closing Contactors A, B or the auxiliary output relays, an OPEN CONTROL CIRCUIT alarm
will occur. This will cause Contactors A, B and the auxiliary relay to open.
If feedback remains at any of the Status N.O. inputs for more than one second after opening its
respective relay, a WELDED CONTACTOR alarm will occur.
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