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CONTROL
Maximum Starting
Rate
NOTE:
4–326
The Maximum Starting Rate element defines the configurable number of start attempts
allowed in a programmable time interval. After every new start, the number of starts
within the past time Interval is compared to the number of starts allowed. When the
maximum number of actual starts within the past Interval is reached, the FlexLogic
operand Max Start Rate PKP is asserted. Once the motor stops, the comparison is
performed again and if the two numbers are the same, the Start Inhibit operand is
activated to block the motor start. If a block occurs, the lockout time is equal to the time
elapsed since the 'oldest start' within the past Interval that occurred, subtracted from the
time of the Interval. For more details, please refer to the figure: Maximum Starting Rate
logic diagram. Even unsuccessful start attempts are logged as starts for this feature.
Example: If Max Number of Starts is programmed at "2" and the time Interval is
programmed at 60 minutes.
•
One start occurs at T = 0 minutes
•
A second start occurs at T = 17 minutes
•
The motor is stopped at T = 33 minutes
•
A block occurs.
•
The lockout time is 60 minutes – 33 minutes = 27 minutes.
If the Emergency Restart input is asserted while the motor is stopped or tripped during a
Maximum Starting Rate lockout, the information about the oldest start inside the selected
time Interval is erased. This causes a dropout of the Start Inhibit and allows a new start. If
the motor starts while the Emergency Restart input is asserted, the new start is still
recorded. It is important that the Emergency Restart is removed either shortly before or
shortly after the motor is started.
Consecutive assertion of multiple Emergency Restart inputs erases the equivalent number
of the oldest motor starts. For example: when an Emergency Restart input is asserted
twice consecutively, the two oldest starts will be erased and therefore allow two motor
starts.
The information about motor starts and stops within the past Interval is stored in non-
volatile memory and remains in the memory after the power is removed from the 869.
When the power is restored, the Maximum Starting Rate element continues working
normally using the information collected before the power loss if the real time clock
worked properly during the power loss. However, when the relay power is restored, if the
clock is not working properly or defaulted to the factory setting, LO time will remain
unchanged and prevent the motor from starting until LO time becomes zero or the
Emergency Restart is asserted.
Path:
Setpoints > Control > Motor Starting > Start Supervision > Maximum Starting Rate
FUNCTION
Range: Disabled, Enabled
Default: Disabled
INTERVAL
Default: 60 min
Range: 1 to 300 min in steps of 1min
This setting specifies time interval for monitoring the maximum allowable rate of
starting. Set it to 60 minutes for the classical starts-per-hour functionality.
MAX NUMBER OF STARTS
Range: 1 to 16 in steps of 1
Default: 3
The setting specifies the maximum allowable number of starts that can occur within the
specified time Interval.
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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