46 Program featuresThe function is also available for scalar motor control with a frequency reference. Theinput of the function is shown by 28.96 Frequency ref act 7, the output by 28.97Frequency ref unlimited.ExampleA fan has vibrations in the range of 540 to 690 rpm and 1380 to 1560 rpm. To makethe drive avoid these speed ranges,• enable the critical speeds function by turning on bit 0 of parameter 22.51 Criticalspeed function, and• set the critical speed ranges as in the figure below.Settings• Critical speeds: parameters 22.51…22.57 (page 210)• Critical frequencies: parameters 28.51…28.57 (page 244). Speed controller autotuneThe speed controller of the drive can be automatically adjusted using the autotunefunction. Autotuning is based on an estimation of the mechanical time constant(inertia) of the motor and machine.The autotune routine will run the motor through a series of acceleration/decelerationcycles, the number of which can be adjusted by parameter 25.40 Autotune repeattimes. Higher values will produce more accurate results, especially if the differencebetween initial and maximum speeds is small.The maximum torque reference used during autotuning will be the initial torque (ie.torque when the routine is activated) plus 25.38 Autotune torque step, unless limitedby the maximum torque limit (parameter group 30 Limits) or the nominal motor torque(99 Motor data). The calculated maximum speed during the routine is the initial speed(ie. speed when the routine is activated) + 25.39 Autotune speed step, unless limitedby 30.12 Maximum speed or 99.09 Motor nominal speed.540690138015601 Par. 22.52 = 540 rpm2 Par. 22.53 = 690 rpm3 Par. 22.54 = 1380 rpm4 Par. 22.55 = 1560 rpm1 2 3 422.01 Speed ref unlimited (rpm)(output of function)22.87 Speed reference act 7 (rpm)(input of function)
