Kollmorgen AKD PDMM series, User Manual

Page: 48 / 513

AKD PDMM User Guide | 7.4.1 Drive Foldback
Foldback is not the same as current limits. Instantaneous current limits for the drive are set by the positive
peak current (IL.LIMITP) and negative peak current (IL.LIMITN) in the Limits view in EWV
1
. The foldback
algorithms may reduce the current output to the motor in spite of the current limit settings.
7.4.1 Drive Foldback
The drive foldback algorithm monitors current feedback; since this is a monitoring function, the drive fold-
back parameters are not user configurable. If the current feedback exceeds the continuous current rating
of the drive (DRV.ICONT), then the algorithm decreases the current to the DRV.ICONT level. For exam-
ple, under a step command input condition, the foldback algorithm allows maximum peak current
(DRV.IPEAK) output from the drive for a short period of time (up to IL.DFOLDD time), after which the
drive begins an exponential foldback (with time constant of IL.DFOLDT) of the current to the drive’s con-
tinuous current.
It takes a few seconds for the exponential decay to drop from the drive’s peak current to its continuous
level. A recovery time, when the feedback current is below DRV.ICONT level, is required to allow current
above DRV.ICONT level again. A recovery time of IL.DFOLDR with 0 current allows the drive to apply
DRV.IPEAK current for IL.DFOLDD time.
7.4.2 Setting up motor foldback
Motor foldback is set up automatically when using a plug and play motor or when a particular motor is
selected from the EWV database.
If you are using a custom motor, use the Motor view in EWV to set custom values needed for foldback
configuration.The parameter entries required for the drive to apply motor foldback protection properly are
coil thermal constant (MOTOR.CTFO), peak current of the motor (MOTOR.IPEAK), and continuous cur-
rent of the motor (MOTOR.ICONT). These values are used to setup the algorithm for motor foldback.
7.4.3 Setting Fault and Warning Levels
The Motor Current Limit and Overall Current Limit boxes show status variables that are constantly
updated by the foldback algorithm. As current is applied above the drive or motor continuous rating, the
capacity for the application of peak current starts to decrease. The motor current limit and overall current
limit are actively decreased. If the move profile requires less than continuous current rating for a period of
time, the Motor Current Limit and Overall Current Limit begin to increase until they reach maximum fold-
back capacity once again.
When Motor Current Limit or Overall Current Limit < Warning Level, an n524 status warning is triggered.
When Motor Current Limit or Overall Current Limit < Fault Level, an F524 fault is triggered and the drive
power stage is disabled. The load then coasts to a stop.
In the Foldback screen, setting the Warning Level to 0 turns off the warning feature. Otherwise, the Warn-
ing Level must be set above the Fault Level, but below the Motor Current Limit and Overall Current Limit to
trigger a warning.
If User Fault Level is set above Fault Level, the User Fault Level will be ignored. The User Fault Level is
used to increase the time the drive is operated in foldback mode without faulting. For instance if the
default Fault Level is 9.000 Arms and a User Fault Level is set to 7.5 Arms, the Fault Level is changed to
1
Embedded Workbench Views
48 Kollmorgen™ | December 2012