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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.