Rockwell Automation 1395 DC Drive, 800-1250 Hp, FRN 5.XX-9.30 - Manual (Page 48)

Chapter 3
Functional Description
3-15
Current Loop Tuning As previously explained, the current loop tuning function performs two
separate functions. First, it checks the armature bridge of the drive to
assure that it is functional. Second, it tests and tunes the current loop gains
of the drive. The current loop function can affect the following
parameters:
Parameter No. Description
734
K Discontinuous
735 KP Armature Loop
736 KI Armature Loop
741 Desired Current Loop Bandwidth
742 Maximum Current Loop Bandwidth
In addition, the parameters listed below are used by the current loop
function during the test and tune procedure. These parameters must be set
up correctly for the tuning function to work properly.
Parameter No. Description
743
Current Loop Damping Factor
733 Armature Bridge Type
Current Test
The Autotune Current Test function requires the DC contactor to close and
armature current to conduct through the DC motor for the diagnostic tests
to work properly and Parameter 734 to be set correctly. Full field is
applied during autotune, slight motor rotation is expected. The diagnostic
tests first check for shorted SCRs by firing one SCR at a time with the DC
contactor open. If current conducts through an SCR, then the software
reports which SCR is shorted. However, the tests cannot identify multiple
shorted SCRs.
Next, the diagnostic tests check for open components (open SCRs, open
gate leads, disconnected motor, etc.) in the armature bridge after the DC
contactor closes. Parameter 733 (Armature Bridge Type), has to be set
properly before the Autotune Current Test is enabled. Otherwise, if the
drive is non-regenerative and contains only six armature SCRs, the
armature tests will erroneously report that the reverse armature bridge did
not conduct (CP-120 REV SCRS DID NOT CONDUCT).
Finally, the average discontinuous current is measured and Parameter 734
(K Discontinuous) is updated. If the maximum discontinuous current
varies from pulse to pulse by too much (12.5 percent of full load), then the
drive will fault. Parameter 734 is a function of the DC motor inductance
connected to the drive. The diagnostic tests also verify that the armature
voltage has the correct polarity while measuring the maximum
discontinuous current or else the tests will report a fault.