Mm3 Sequences - GE MM3 Instruction Manual

9 STARTER TYPES 9.3 TWO SPEED STARTER

9.3.2 MM3 SEQUENCES

START LOW SPEED sequence:
1. Start A command received by the MM3 (serial, switch input or faceplate).
2. Close and maintain Contactor A relay – the motor is now in low speed.
START DIRECTLY TO HIGH SPEED (motor stopped, HIGH SPEED START BLOCK not enabled) sequence:
1. Start B command received by the MM3 (serial, switch input or faceplate).
2. Close and maintain Contactor B relay – the motor is now in high speed.
START DIRECTLY TO HIGH SPEED (motor stopped, HIGH SPEED START BLOCK enabled) sequence:
1. Start B command received by the MM3 (serial, switch input or faceplate).
2. No response to start B commands.
LOW TO HIGH SPEED TRANSITION sequence:
1. Start B command is received (serial, switch input or faceplate).
2. Open contactor A output relay.
3. Close and maintain Contactor B relay – the motor is now in high speed.
HIGH TO LOW SPEED TRANSITION sequence:
1. Start A command is received (serial, switch input or faceplate).
2. Open contactor B output relay.
3. Wait for the programmed transfer time.
4. Close and maintain contactor A.
STOP/TRIP sequence:
1. Stop command received by the MM3 or a trip occurs.
2. Open the currently closed contactor output relay.
There are many different configurations for the TWO SPEED starter type. Three of the more popular ones are
illustrated here: two-speed one winding constant or variable torque, two-speed one winding constant horse-
power, and two-speed two winding. See the two speed starter diagrams on the following pages.
When the power to the MM3 is interrupted, all MM3 output relays de-energize, causing them to open and stop
the motor. The MM3 can only be wired for fail-safe operation.
If feedback is not received from the L or H contacts to the Contactor A or B Status N.O. input within one second
of closing Contactor A relay, an OPEN CONTROL CIRCUIT alarm will occur. This will cause Contactor A and B
output relays to open.
If feedback remains at the Contactor A or B Status N.O. input more than one second after opening the Contac-
tor A or B output relays, a WELDED CONTACTOR alarm will occur.
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GE Power Management MM3 Motor Manager 3 9-7