Questions And Answers - GE MOTOR MANAGER 2 Instruction Manual

APPENDIX B
APPENDIX B MM2 FAQB.1 MM2 FAQ
Listed below are some of the more frequently asked questions by MM2 users. The list includes ques-
tions asked by consultants before the MM2 has even been specified to the end user and after the
MM2 is installed and controlling a motor.
Q
Does the MM2 support ladder logic as in a PLC?
No. The MM2 switch inputs do not allow total programmability as in PLCs; however, it does
A
have a range of over 30 different dedicated functions that can be assigned for typical appli-
cations. These functions come complete with built in timers if necessary for that particular
function. For example: Auto Permissive and Auto Start for PLC hard wired control, Two Wire
Control for PLC starts or jogging, Process Interlocks with starting and running override tim-
ers for pressure and flow monitoring. All the programmable switch inputs may be configured
as normally open or normally closed.
Q
Does the MM2 have any hot winding protection?
Yes. The MM2 has a single thermistor input to protect the motor against hot windings. These
A
thermistors are typically wound into stator windings of the motor when manufactured and
can be Positive Temperature Coefficient (PTC) of Negative Temperature Coefficient (NTC).
After wiring the MM2 into the control circuit, it remains UNAVAILABLE for starts.
Q
What does this mean?
Three conditions can cause the MM2 to remain UNAVAILABLE for starts"
A
The MM2 has tripped on a trip condition
The STOP switch input (terminal 11) is not energized.
If a Process Interlock function is assigned to one of the programmable switch inputs and the
startup override is set to 0 seconds, the MM2 will remain UNAVAILABLE until that switch
input is energized.
When a start is attempted, the motor starts for a second then shuts off. The MM2 dis-
Q
plays an OPEN CONTROL CIRCUIT alarm. What is the problem?
The MM2 must see feedback from the Contactor A and, if used, Contactor B within 1 second
A
of the MM2 closing the contactor or the MM2 will stop the motor as it assumes that there is
a problem in the circuitry for the motor contactor coil. The feedback from the contactors go
to the status inputs (terminals 15 & 16) of the MM2. NOTE: This condition will result in the
toggling of the motor contactor when the MM2 is in the Two Wire mode as there can be a
constant start signal from the two wire device. Use the Open Control Circuit trip feature to
prevent the toggling of the motor contactor.
GE Power Management
MM2 Motor Manager 2
B.1 MM2 FAQ
B.1.1 QUESTIONS AND ANSWERS
B
B-1