Malfunctions Not Indicated by a Fault
3-5
The motor is rotating at the
wrong velocity.
(continued)
The motor velocity is incorrect, but
remains constant during varying loads.
(continued)
•
If Armature Voltage Feedback is selected verify that parameter
610 “Rated Motor Volt” and parameter 606 “Base Motor
Speed” are correctly entered according to the motor nameplate
data. Also verify that parameter 739 “K Arm Volts” is properly
scaled to the drive voltage rating. Verify that the field is
functioning properly by checking that parameter 612 “Rated Fld
Mtr Cur” reflects the rated field current on the motor nameplate.
Enter the fields bridge rating as determined by the jumper
setting on the Feedback board and the drive nameplate rating,
in parameter 616 “Rated Fld Brdg I”. The field bridge jumper
should select the current rating that is just above the motor
field rating.
•
If an analog tachometer is used, verify that the offset and
scaling parameters associated with the adapter’s analog input
channel are correctly set-up.
The motor velocity decreases when the
load on the motor increases. Torque
varies proportional to the load.
•
The Droop function is incorrectly activated or set-up. Droop
allows the velocity to decrease as a function of load torque. As
the load on the motor increases the final velocity reference will
decrease based on the values of the set-up parameters for the
droop function. If parameter 103 is equal to the desired velocity
reference but parameter 104 “Final Vel Ref” is not, then the
Droop control is affecting the reference.
Parameter 657 “Droop Percent” sets the reduction in velocity, in
percentage of base speed, that will occur at rated load. Parameter
658 “Droop Filter” determines the gain of a low pass filter which
effects the response of the reduction in velocity due to an increase
in load.
The motor velocity decreases due to
insufficient motor torque being
commanded for the load present. Torque
command remains constant or
decreases.
•
The torque taper control may be limiting the torque command.
Torque taper is used to reduce the current limit as a function of
speed. Set-up is accomplished through parameter 665 “Strt
Taper Speed” which sets the velocity at which the maximum
torque will begin to be limited. Parameter 666 “End Taper
Speed” which set the velocity where the maximum torque will
be fully limited, and parameter 667 “Min Taper Cur” which sets
the maximum torque level at end taper speed. Verify that this
function is properly set-up and not interfering with normal
operation.
The motor velocity decreases due to
insufficient armature current being
output to the motor. The torque
command accurately reflects the output
from the velocity regulator but the
corresponding armature current
reference remains constant or
decreases.
•
The armature current reference, parameter 111 “Arm Current
Ref” is being limited by the forward or reverse armature current
bridge limits. Parameter 663 “Fwd Brdg Cur Lim” specifies the
forward bridge limit while parameter 664 “Rev Brdg Cur Lim”
specifies the limit for the reverse bridge. Verify that these
parameters are properly set-up to allow for normal operation.
•
The motor or bridge set-up parameters are incorrectly entered.
Verify that parameter 611 “Motor FLA” and parameter 615
“Rated Arm Brgd I” are properly entered. These effect the
scaling of torque command to armature current reference.
Velocity Control Malfunctions
Malfunction
Symptom
Solution
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