Rockwell Automation 1557 MEDIUM VOLTAGE AC DRIVE - Manual (Page 238)

9-38 COMMISSIONING
1557-UM050F-EN-P – June 2013
Reg in limit - indicates that the torque command was greater than "Torque limit motoring" or "Torque limit
braking". The measured inertia value is invalid. Parameter "Autotune trq stp" or parameter "Autotune spd cmd"
must be set to a lower value and the test repeated.
Tuning abort - indicates that the deviation in motor speed was greater than 10 Hz. The measured inertia value is
invalid. Parameter "Autotune trq stp" must be set to a lower value and the test repeated.
Inertia high - indicates that the measured total inertia was greater than 5 seconds. This warning is intended to
draw attention to an unusually high inertia value. For a very high inertia load such as a large fan, this may be a
valid result and parameter "Total inertia" should be manually set equal to "Autotune inertia". However, a high
inertia measurement could also be produced by a value of "Autotune trq stp" which is too low.
Speed Regulator Manual Tuning
If it is not possible to tune the speed regulator using the autotune function, then the step response of the speed
regulator can be tuned manually using the following procedure. To obtain accurate results, the load torque
must be steady.
1.
Set parameter "Spdreg bandwidth” in “P Speed Control” to 1.0 rad/sec.
Speed Control Parameter Screen
2.
Set parameter "Total inertia" in “P Speed Control” to an initial value of 1.0 sec.
3.
Assi gn variable "Speed error” in “V Speed Control” to one of the line converter analog outputs (1 to 4)
and display it on a digital storage oscilloscope set to 2 V/division vertical and 1 sec/division horizontal.
These variables may be assigned the same way the external meters were assigned.
4.
Adjust the speed command to a value around the middle of the operating speed range.
5.
Start the drive and wait for it to accelerate to the commanded speed.
6.
Set parameter "Speed ref step" in “P Speed Control” to 0.8 Hz. The drive speed will step up and down by
this amount at regular intervals. The step of 0.8 Hz corresponds to 4 V on the analog output. Since the
speed error signal has a range of only 4 Hz in order to achieve the required resolution for small changes
in speed, the signal may sometimes rollover (jump from +10V to -10V) during the speed step. If this
occurs, it can be eliminated by adjusting the speed command up or down slightly.
7.
Adjust the value of parameter "Total inertia " until the speed rises to approximately 63% of its final value
in 1 second as shown in the figure. If the response time is too fast it indicates that “Total inertia” is set
too high and should be decreased. If the response is too slow then “Total inertia” is set too low and
should be increased.