0 5 . PR OT EC T I O N F U N C T I O N S 53
Start limitation
Start limitation helps to protect the motor and
also the process against excess number of starts
in a given interval. When the number of starts is
reached and the motor is switched off, a new
start is prevented. The time interval, starts from
the first start. After the elapse of the time
interval, the counter is reset to the preset value.
The permissible motor starts per hour can be
obtained from the manufacturer's motor and
apparatus data sheet. However, the minimum
waiting time between two starts must be
observed.
The parameterization of the protection function
can be the number of starts per time interval or
the time between two consecutive starts. In the
first case, the user must wait after the trip for the
reset to take place before making a start.
If motor data specifies the number of starts
during a certain time span, this function can be
used to supervise the number of starts. In some
other cases, the process may require a motor
start number, which the protection can provide.
Functionality is presented in the following
example. The next Figure 42 illustrates the start
limitation protection with 3 starts allowed.
1) Normal situation, after stop command motor
can be started normally, start 2. Every start
activates an internal timer for the time defined
by time interval parameter. The number of
active timers are reviewed after every stop
command and compared to value of number of
starts parameter. Stop command can be
implemented during active or elapsed timer.
2) Two timers are still active, thus stop command
generates alarm message start limitation alarm
and one more start, Start 3 is allowed.
3) The 3rd start has been executed. A contactor
trip and trip message start limitation trip
alarm will follow when motor is stopped while
there are two active timers, starting from Start 1.
4) Trip can be automatically reset when the first
timer from Start 1 is finished. Motor start is
possible when all pending trips are reset.
Supervision continues with a new timer from
Start 4.
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42 Start limitation protection
Function
Setting range 0=Disable 1=Enable
Default value Disabled
Step value 1
Time interval
Setting range 1-600min
Default value 1min
Step value 1
Number of starts
Setting range 2-100
Default value 2
Step value 1
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