Troubleshooting; Frequently Asked Questions - Danfoss VLT 5000 Operating Instructions Manual

Troubleshooting

Frequently asked questions

Q1:
When I have a "PID TRACK ERROR TOO BIG"
error (P798="9"), the inverter also trips on ALARM
13 (OVER CURRENT).
A1:
a) Check that the velocity setting (P723 for jogging
and P738/P742 for positioning) is at least 5% lower
than the maximum allowed velocity calculated in
P799. Either lower the velocity (P723 or P742)
setting or raise the maximum allowed velocity
(P799) by setting a higher value of P205 - please
see Q2.
b) The quick stop ramp time (P719) could be too
short. Try to increase the setting.
Q2:
How do I adjust the maximum allowed velocity in
P799?
A2:
You need to raise the setting of P205. Doing this
will also affect the performance of the parameters
P702, P703, P704, P707 and P708. Smaller
changes to P205 may not have any noticeable
effect on most of these parameters but P707
should always be recalculated using the auto-
calculation function P710.
Q3:
The inverter frequently trips on ALARM 7 (DC LINK
OVERVOLTAGE) while ramping down.
A3:
a) Use a higher ramp time setting (P719 for "quick
stop", P724 for jogging and P738/P741 for posi-
tioning).
b) If a lower ramp time is required a brake resistor
should be installed.
MG.50.P3.02 - VLT is a registered Danfoss trademark
Positioning Controller
Q4:
The inverter frequently trips on ALARM 13 (OVER
CURRENT) while ramping up
A4:
a) The ramp settings may require too much torque.
Try to determine which operation ("quick stop",
manual move or positioning) caused the trip, and
then set the corresponding ramp time (P719 for
"quick stop", P724 for jogging and P738/P741 for
positioning) with a higher ramp time setting.
b) The PID controller settings may be unstable –
re-optimise the PID controller parameters (P702-
P709).
Q5:
The correct target position is reached, but the PID
tracking error (P797) is too big while the drive
moves.
A5:
Harder settings of the PID controller may be requi-
red – re-optimise the PID controller parameters
(P702-P709).
Q6:
The option sometimes seems to forget changes to
parameter values.
A6:
Changes to parameter values are not stored after
power-down unless P777 (STORE DATA) is acti-
vated before power-down.
Changes to trajectory data P705-P709 in
POSITIONING MODE is ignored unless the correct
password is entered in P778.
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