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S4 CONTROL
NOTE:
NOTE
NOTE:
NOTE
6–146
This function enforces a settable minimum time duration between two successive start
attempts. A time delay is initiated with every start attempt, and a restart is not allowed
until the specified interval has lapsed. This timer feature may be useful in enforcing the
duty limits of starting resistors or starting autotransformers. It may also be used to restrict
jogging.
This element assumes a motor start is occurring when the relay measures the transition of
no motor current to some value of motor current. At this point, the Time Between Starts
timer is loaded with the entered time. Even unsuccessful start attempts will be logged as
starts for this feature. Once the motor is stopped, if the time elapsed since the most recent
start is less than the TIME BETWEEN START setting, the Start Inhibit Output Relay will be
activated to block the motor start. If a block occurs, the lockout time will be equal to the
time elapsed since the most recent start subtracted from the TIME BETWEEN START setting.
For example, if TIME BETWEEN START is programmed as 25 min:
•
A start occurs at T = 0 minutes
•
The motor is stopped at T = 12 minutes
•
A block occurs
•
The lockout time would be 25 minutes – 12 minutes = 13 minutes
Restart Inhibit
The Restart Inhibit feature may be used to ensure that a certain amount of time passes
between the time a motor is stopped and the restarting of that motor. This timer feature
may be very useful for some process applications or motor considerations. If a motor is on
a down-hole pump, after the motor stops, the liquid may fall back down the pipe and spin
the rotor backwards. It would be very undesirable to start the motor at this time.
This element assumes a motor stop is occurring when the relay measures the transition of
some value of motor current to no motor current.
For each of these features, non-volatile memory is used to make it behave as if it
continues to operate while control power is lost.
THERMAL INHIBIT
Range: OFF, 0 to 25% in steps of 1%
Default: 10%
OFF disables thermal start inhibits. 0% causes starts to be inhibited until the value of
thermal capacity used calculated by the thermal model drops to 15% or less. Setting
values in the range of 1 to 25% specify the margin to be included in the calculation of
the learned thermal capacity used at start, and cause starts to be inhibited until the
value of thermal capacity used drops to the learned thermal capacity used at start or
less.
STARTS/HOUR LIMIT
Range: OFF, 1 to 5 in steps of 1
Default: OFF
Sets the number of starts in the last 60 minutes at which count start control is inhibited.
OFF defeats this feature.
TIME BETWEEN STARTS
Range: OFF, 1 to 3600 s in steps of 1 s
Default: OFF
Sets the amount of time following a start before the next start control is permitted to
prevent restart attempts in quick succession (jogging). OFF defeats this feature.
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: SETPOINTS
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