Lenze SCF frequency inverter - Manual (Page 63)

Lenze 13466146 EDBSF01 v24 EN
63
Appendix
P74 ANALOG INPUT FILTER
This adjusts the filter on the analog input terminals (TB-5 and TB-25) to reduce the effect of any electrical
noise that may be present on the analog input signals. This filter works both in PI mode and standard
speed control mode. It should be set to the lowest value that yields acceptable performance, as setting
it too high may cause the drive to react too slowly to signal changes. The range of adjustment is 1 to
1000, which actually corresponds to 0.01 to 10.0 seconds.
P75 SLEEP THRESHOLD
The PI option has a Sleep Mode function that allows the drive to cease operation when system
demand falls below a preset level. This is to prevent the the motor from operating at low speeds for
long periods of time.
When the commanded speed falls below the SLEEP THRESHOLD setting for the defined SLEEP DELAY
time (see P76 below), the drive will "go to sleep" and the motor will stop. The drive will remain
"sleeping" until the it is commanded to operate at a speed that is 2 Hz above the SLEEP THRESHOLD,
at which point it will "wake up" and ramp the motor up to the commanded speed.
NOTE
• While the drive is in Sleep Mode, the display will read "SLP".
• If the drive's commanded speed goes below the SLEEP THRESHOLD, the SLEEP DELAY
timer will start to count down. If the commanded speed equals or exceeds the
SLEEP THRESHOLD before the SLEEP DELAY times out, the SLEEP DELAY timer will be
reset.
• If the drive is in a Stop state, and the commanded speed is below the SLEEP
THRESHOLD, the drive will immediately go to sleep upon a Start command,
bypassing the SLEEP DELAY.
P76 SLEEP DELAY
This sets the amount of time the drive must operate below the SLEEP THRESHOLD (see P75 above)
before the drive "goes to sleep" and brings the motor to zero speed.
Example: SLEEP THRESHOLD is set to 15 Hz and SLEEP DELAY is set to 60 seconds. If the drive operates
below 15 Hz for 60 seconds, the drive will go to sleep and the motor will stop. The drive will display
"SLP", and the drive will remain sleeping until the drive is commanded to a speed equal to or greater
than 17 Hz. At this point, the drive will wake up and and ramp the motor up to the commanded
speed. This example assumes that SLEEP BANDWIDTH (P77) is set to 0.
P77 SLEEP BANDWIDTH
This allows the PI feedback signal to determine when the drive should "wake up" when operating in
Sleep Mode. In process systems that utilize Integral Gain (see P65), the drive may cycle in and out of
Sleep Mode more often than desired, due to the Integral function of the PID algorithm.
When SLEEP BANDWIDTH is used, the feedback signal must change by the programmed amount
before the drive will wake up.
Example: In a normal-acting system, the PI setpoint is 50 PSI, SLEEP THRESHOLD is set to 20 Hz, and
SLEEP BANDWIDTH is set to 5 PSI. The drive will enter Sleep Mode when the commanded speed
drops below 20 Hz for the time defined in SLEEP DELAY. The drive will wake up when the feedback
signal drops below 45 PSI (50 PSI setpoint minus 5 PSI bandwidth = 45 PSI), even if the commanded
speed is still below 20 Hz.