LEESON Micro Series Compact Inverters User Manual

Page 67

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’s

display will indicate SLEEP, and the drive will remain “sleeping” until the drive commanded to a speed

equal to greater than 17 Hz. At this point, the drive will “wake up” and ramp the motor up to the

commanded speed .

SLEEP BW

(SLEEP BANDWIDTH)

This parameter allows the PID feedback signal to determine when drive should “wake up” when operating

in Sleep Mode. In process systems that utilize Integral Gain (see Parameter 78), 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 decrease or increase (depending on whether

the system is normal or reverse-acting) by the programmed amount before the drive will “wake up”. This

parameter is set in PID units .

Example:

In a normal-acting system, the PID set point 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 set point minus 5 PSI bandwidth = 45 PSI), even if the commanded

speed is still below 20 Hz.

NOTE:

If SLEEP BANDWIDTH is set to 0, this function is disabled, and the drive will wake up when the

commanded speed exceeds the SLEEP THRESHOLD plus 2 Hz, as described in Parameters 36 and 37.

TB5 MIN

(TERMINAL TB-5 INPUT)

TB5 MIN selects the output frequency of the drive that will correspond to the minimum analog speed

reference input (0 VDC or 4 mA). This parameter is used in conjunction with Parameter 40 - TB5 MAX

to define a speed range that corresponds to the analog speed reference input (0 - 10 VDC or 4 - 20 mA).

TB5 MAX

(TERMINAL TB-5 INPUT)

TB5 MAX selects the output frequency of the drive that will correspond to the maximum analog speed

reference input (10 VDC or 20 mA). This parameter is used in conjunction with Parameter 39 - TB5 MIN

to define a speed range that corresponds to the analog speed reference input (0 - 10 VDC or 4 - 20 mA).

Example 1:

The drive is required to operate from 0 to 60 Hz in response to a 0-5 VDC speed reference

signal (rather than the “normal” 0-10 VDC). Because TB5 MAX is based on a 0-10 VDC (or 4-20 mA)

signal, the drive will operate at half of the TB5 MAX value if it is given a 5 VDC signal . Therefore, setting

TB5 MAX to 120 Hz will cause the drive to run at 60 Hz when it is given a 5 VDC speed reference signal.

NOTE:

The drive can be programmed for inverse operation so that as the speed reference increases, the drive

speed will decrease, and as the speed reference decreases, the drive speed will increase . This is accomplished

by setting TB5 MIN to the desired maximum output frequency, and TB5 MAX to the desired minimum

output frequency.

Example 2:

The drive is being controlled by a pressure transducer that provides a 4-20 mA signal

proportional to duct pressure. The minimum frequency desired is 20 Hz, and the maximum is 60 Hz. Set

TB5 MIN for 60 Hz, and TB5 MAX for 20 Hz. As the duct pressure rises, the output signal from the

transducer will increase, causing the speed of the drive to decrease . This results in a decrease in duct pressure

and a decreasing transducer signal . The drive responds to the decreasing signal by increasing speed, which

again raises the duct pressure . In this way, the average duct pressure can be maintained at a certain level . If

the acceleration and deceleration rates are set too fast however, the drive will react quickly to signal changes

which will cause the drive speed to “hunt” up and down excessively.