Download LKP MODULE DIAGNOSTIC PROCEDURE rev3

LKP DIAGNOSTIC / TROUBLESHOOTING GUIDE
This document is intended to provide electrical technicians with a troubleshooting
guide for LKP High Current Measurement Systems. LKP systems have between 1
electronics module ( LKP-6, 12, 15, 30 ) and up to 6 electronics modules. This
troubleshooting guide addresses troubleshooting on a module by module basis.
Each module typically has 4 channels ( some models, such as LKP45, may have a
module with only 2 channels which is obvious by the reduction in electrical
connections ).
The input to each channel is connected to a Hall Plate magnetic sensor in the
measurement head. The output of each channel provides compensation current to
coils in the measurement head.
When a channel is operating correctly, the module increases compensation current to
the point where the Hall Plate output is driven very close to zero. If one or more
channels are not operating in this manner, significant measurement errors can
occur.
1)
LOCATE THE PROBLEM CHANNEL WHILE THE LKP IS OPERATING ON A LIVE BUS BAR
Check the channel voltages to demonstrate that the closed-loop feedback
(compensation current ) is working correctly.
Connect the negative (-) lead of the multimeter to
terminal 18, 19, 20, or 21 (they are wired together)
Now use the positive lead measure the feedback voltage
of each channel as follows:
terminal 14(+) for channel 1
terminal 15(+) for channel 2
terminal 16(+) for channel 3
terminal 17(+) for channel 4
If the system is operating correctly, and the bus bar has live current, the
channel voltages will differ due to external magnetic fields but should be
between 3V and 30V.
If this check shows a channel that either has very high or very low voltage,
measure the hall plate output voltages of each channel.
terminals 6(-) and 7(+) for channel 1
terminals 8(-) and 9(+) for channel 2
terminals 10(-) and 11(+) for channel 3
terminals 12(-) and 13(+) for channel 4
On a ‘good’ LKP system, the Hall plate voltage is typically 0 to 5mV.
If the reading is a solid zero and not fluctuating, there could be a problem
with the Hall plate or with the wiring between the electronics and the
Hall plate.
If you find a channel not operating correctly, additional tests can be performed to
identify where the problem is. It could be inside the measurement head, inside the
electronics module or in the wiring between them. To continue testing, the LKP
must be switched off and on, some simple wiring changes may be done, etc. During
the following steps, the LKP measurement output signal should not be used.
2) CHECK THE CLOSED LOOP FEEDBACK FUSES WHILE LKP IS OPERATING ON A LIVE BUS BAR
---!During this process, the LKP measurement output signal should not be used!--Switch the LKP system off
One at a time, remove each fuse in the front panel of the metering
electronics and ohm-check using a multimeter.
If no bad fuse is found, leave the fuses out and proceed to step 3)
If a bad fuse is found, be sure to note the channel.
( It should be the same channel as the bad channel identified in
step 1 above ) Replace the fuse with one of the same type as
specified in the LKP users manual.
After replacing the bad fuse, and putting all fuses back in place,
switch the LKP power on to see if the LKP operates OK or if it
will blow the fuse again. To do this, check channel voltages.
Connect the negative (-) lead of the multimeter to
terminal 18, 19, 20, or 21 (they are wired together)
Now connect the positive lead of the mulimeter as follows:
terminal 14(+) for channel 1
terminal 15(+) for channel 2
terminal 16(+) for channel 3
terminal 17(+) for channel 4
If all channels appear to have normal operating voltages, a blown
fuse was the problem. However, remember that the fuses protect
the system and something must have caused the fuse to clear.
Send all taken voltages ( Hall plate and channel voltages ) to
DynAmp for technical analysis. Continue to step 5)
If the fuse clears again, or no cleared fuses were found,
additional tests need to be performed. Continue to step 3)
3) TEST THE HALL PLATE SIGNALS WITHOUT THE CLOSED LOOP FEEDBACK CIRCUITRY ACTIVE
---!During this process, the LKP measurement output signal should not be used!--Switch the LKP system off
Remove all the fuses
After the fuses are removed, and with the bus energized, switch the LKP back
on, and measure each channel hall plate output again with a multimeter :
terminals 6(-) and 7(+) for channel 1
terminals 8(-) and 9(+) for channel 2
terminals 10(-) and 11(+) for channel 3
terminals 12(-) and 13(+) for channel 4
Because the system is operating without any compensation current in this
condition, each Hall plate voltage should be approximately 0.4V (400mV)in
this case.
If this test is successful, and the Hall plates appear to be operating
correctly. proceed to step 4) below
If this test indicates a problem, Switch off the LKP and check connections
between the terminal strip and the head cable( no insulation
trapped under the screw, etc. ) If the connections are good, note the
channel number/terminals of the problem and proceed to step 4.
4) IDENTIFY WHERE THE PROBLEM IS LOCATED
In summary, this is done by switching a channel set of Hall and Feedback
connections with another set at the metering electronics. This will identify if
the problem is in the electronics or in the cabling/head. For example, if there is
a problem in channel 2, we recommend switching the set of connections related to
channel 2 with channel 4. If there is a problem in Channel 1, we recommend
switching the set of connections related to channel 1 with channel 3.
- If the problem "stays" on the same terminals after the connections are changed,
the problem is inside the metering electronics.
- If the problem "moves" to the other terminals after the connections are changed,
the problem is in the cabling or measurement head.
If this process is unclear, or the next steps seem too complicated, we recommend
contacting DynAmp with the information already collected. DynAmp will review and
provide specific instructions regarding the final troubleshooting steps.
---!During this process, the LKP measurement output signal should not be used!-----CAUTION--If the measurement head is still on a live bus and even if the LKP is switched off,
there will be a voltage potential present in the feedback coil circuit due to the
coils being in the strong magnetic field generated by the energized bus bar. When
disconnecting the wires from the terminal strip, immediately cover with insulating
electrical tape to prevent a small shock to the technician. This will also prevent
possible damage to the system if the unprotected lead touches a terminal or lead to
sensitive electrical components.
Switch the LKP system off
TO SWAP CHANNEL 2 AND CHANNEL 4 CONNECTIONS
Hall: Move the wire on terminal 8 to 12 and the wire from 12 to 8
Move the wire on terminal 9 to 13 and the wire from 13 to 9
Loop: Move the wire on terminal 15 to 17 and the wire from 17 to 15
TO SWAP CHANNEL 1 AND CHANNEL 3 CONNECTIONS
Hall: Move the wire on terminal 6 to 10 and the wire from 10 to 6
Move the wire on terminal 7 to 11 and the wire from 11 to 7
Loop: Move the wire on terminal 14 to 16 and the wire from 16 to 14
Now, repeat the tests outlined in steps 1
- If the problem "stays" on the same terminals, then the problem
is in the metering electronics
- If the problem "moves" to new terminals, then the problem
is in the cabling or inside the head
Once all the tests are complete, switch the LKP off and be sure to move all
connections back to the original terminals.
--- BE SURE TO OBSERVE THE CAUTION ABOVE BEFORE CONTINUING --First, switch the Hall plate signal leads back to the original position
Second, switch the feedback coil circuit leads back to the original position
5)
SEND RESULTS TO DYNAMP SO PROMPT REPAIR OR REPLACEMENT CAN BE ORGANIZED.
If this troubleshooting process indicates that the problem is in the
electronics, a replacement electronics module can be ordered for the technician to
install. In this case, many customer return the faulty module to DynAmp for repair
so that the customer can have a spare module on-hand. Another option is to return
the faulty electronics module to DynAmp for repair.
If this troubleshooting process indicates that the problem is in the
cabling/measurement head, a replacement head can be ordered for the technician to
install. Another option is to request that a DynAmp technician visit the site to
try to repair the head.
DynAmp also has a small selection of measurement systems that are available
for short term rental. In this case, the rental system can be installed by the
customer so the faulty system can be returned to DynAmp for repair.