CHAPTER 4: SETPOINTS CONTROL ELEMENTS
MM200 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL 4–27
The traditional algorithm would detect the start (if it is fast enough), but may or may not
detect the running state that follows. Even if it does detect the running state, as it is an
atypical start, the learned values such as learned acceleration time would be corrupted.
The MM200 employs an improved starting and running state detection algorithm.
Normally, it declares starting when either contactor A or contactor B closes. Running is
declared when either contactor has been closed for one second, and then current is found
to be below 1 × FLA. This provides equivalent functionality to the traditional algorithm..
If an A or B motor contactor is externally energized, the relay will treat this as a start A or B
control, and display an
External Start A Alarm or an External Start B Alarm message.
The stop/start control element also consolidates the various start and stop signals for the
convenience of other elements.
The following setpoint is available:
External Stop Action
Range: Stop, Trip
Default: Stop
This setpoints selects whether an external stop is considered to be an emergency stop
(reset required to clear) or a stop control (no reset required).
Power failure restart
The Power Failure Restart element (PFR) provides a relay-initiated undervoltage motor
restart after a momentary power loss (dip).
The undervoltage is detected by a digital input associated with an External Voltage Relay.
When the auxiliary voltage supply drops below the pre-set low voltage level, the motor
contactor(s) are de-energized until the dip is ended as indicated by supply recovery to the
pre-set high voltage level.
• The motor will be switched back to its previous status if the voltage returns within the
“Power Failure Time”. This can either take place immediately or be further delayed
(Power Failure Restart Time).
If the motor was running at the time the dip occurred, a forced restart will occur as soon as
the relay detects healthy auxiliary voltage and the restart time delay has expired.
If the motor was not running at the start of the dip, no restart sequence will be initiated.
Start controls are ignored while the PFR delay is timing out. While the PFR timer is counting
down, the status will change to “PFR Pending”. During PFR Pending, any stop or trip will
immediately cancel the restart sequence.
With MM200 power supply voltage derived from the incoming motor supply, the MM200
will experience the same interruption as the motor. The MM200 has not been designed to
ride through power outages of up to 200ms and the power failure restart is affected by this
condition, so with an outage higher than 200 ms the relay will be powered off. When the
control supply recovers, the relay will not initiate any motor start.
PFM Function
Range: Enabled, Disabled
Default: Disabled
Enables the Power Failure Restart function.
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