Siemens Industry, Inc. 92
How to Fine Tune Tap Tracking
If you have tap tracking problems, there are some steps to systematically make adjustments to
the settings in order to improve the performance of the tap tracking algorithm. First, identify any
Tap Track Err trouble codes. Second, verify whether or not the tap position in memory under
the <COUNTERS> menu is correct. Third, operate the voltage regulator up or down a few
steps out of band and let it make automatic tap changes to come back in band.
When running the tap changer, there are a few things to make note of:
Does the Total Operations counter increase with each and every tap change?
Does the Raise or Lower light on the MJ-XL turn on while the tap changer motor is
running?
How quickly does the Op Counter increase after the tap change is complete?
Observe the “Tap=” screen under <COUNTERS> during the tap change operations.
When does it track properly and when does it not? Is there a difference between
Auto/Manual operations or between Raise/Lower operations?
If the control doesn’t count operations, check the signal from the voltage regulator to be sure it
is functional; without an op counter, no regulator control can track tap position. The MJ-X
L
has
tiny CT’s on the circuit board to sense current to the motor in the raise and lower direction.
When the current exceeds a threshold, the Raise or Lower LED will illuminate. If it isn’t lighting
up during a tap change, or is turning off before the tap change occurs, then the control could
have trouble tracking the direction of the tap change. If the operations counter takes a long time
to increment, the operations count switch in the tank might be worn and need replacement. For
pulse type counters, the TapInPulse may just need to be adjusted.
Tap Changer Variations
For Siemens tap changers, the default settings should be OK and typically require no
adjustment. In some cases, you may increase “R/LOnTime” from the default of 8.0 seconds to
a higher value if you find that tap changes are taking longer than 8.0 seconds and Tap Track Err
OD alerts are being generated. Siemens tap changers use a toggle type operations counter;
there will be ~120VAC on U10 on odd positions and ~0VAC for even positions. The neutral
signal (U12) will have ~120VAC for all non-neutral positions and ~0VAC on neutral.
GE tap changers have a pulse type operations counter that is closed for a fraction of a second
immediately after a tap change completes. GE’s neutral signal will have ~120VAC for all non-
neutral positions and ~0VAC on neutral. Occasionally, it may be necessary to adjust the
TapInPulse to increase or decrease the sensitivity of the operations counter sensing.
Cooper has had three different tap changer designs: the Spring Drive, the Direct Drive, and the
Quick Drive (similar to Direct Drive). Cooper’s neutral signal will have ~0VAC for all non-neutral
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