Continued
n094 : Sleep Function Start Level Factory setting: 0.0 Hz
(Sleep Start Lvl)
Range: 0.0 to 400.0 Hz
n095 : Sleep Function Delay Time Factory setting: 0.0 seconds
(Sleep Delay Time)
Range: 0.00 to 25.5 seconds
This function provides a deadband in drive operation that increases control flexibility, and a
scheme to reduce unnecessary operation of the equipment. It is useful for applications
which require a minimum operating speed. For example, a pump may have to move at 25%
rated speed in order to move liquid. When using the sleep function, a sensed variable like
temperature or pressure must deviate by a large enough amount before the drive is allowed
to run. For example, the temperature in a space may be allowed to drift past a set point by
so many degrees before a fan is started. When the signal from the sensed variable is below
a certain point, the drive and motor are off.
This function operates when parameter n094 (Sleep function start level) is set to some
value other than zero and one of the PID modes is selected (n084is "Enabled"). The drive
starts to run when the PID output (frequency reference) is higher than the setting specified
in parameter n094 for longer than the time entered into parameter n095 (Sleep function
delay time) has elapsed. The drive stops running when the PID output drops below the value
in parameter n094 for longer than the time entered into parameter n095.
Sleep Function Timing Chart
See timing chart:
1. The drive is stopped.
2. External Run is closed, but the PID output is below the sleep function start level (n094). The
drive remains stopped.
3. The PID output exceeds the sleep function start level (n094), and the sleep function time delay
timer (n095) starts timing.
4. The sleep function delay timer (n095) expires and the drive accelerates on the acceleration ramp
to “catch up” with PID output. The drive then follows the PID output.
5. The PID output level falls below the sleep function start level (n094). The sleep function time
delay timer (n095) starts timing. The drive still follows PID output.
6. The sleep function delay timer (n095) expires and the drive decelerates on the deceleration ramp.
5.22 PID CONTROL
5-49
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