After power on, the main operation indicator light of the motor protection controller remains on, but the display module is not working properly Possible cause: Poor contact of the dedicated DB9 connection wire connecting the controller body and display module (or broken wire due to bending) Solution: After powering off, plug and unplug again, then tighten the DB9 connection cable or replace it with a new DB9 connection cable.   2. Abnormal contactor action during no-load test control circuit When debugging the control circuit with no load, when the controller receives a start command from the display module button or DI terminal, the contactor is immediately released after being powered on and closed for 2 seconds, and cannot maintain a closed state; After the corresponding display module's "Start Interface" progress bar displays for 2 seconds, returning to the "Start Ready" interface may result in relay tampering. Possible reason: In addition to the "protection mode", in other control methods, the controller will detect the main circuit current to determine whether the startup is normal; If a start command is received, the main relay controlling the contactor circuit is closed, and the contactor is energized and closed. If the main circuit current does not reach 10% or more of the rated current after 2 seconds, it is considered that the motor is not running, and the relay is disconnected, and the contactor is released after losing power. Solution (choose any one): 1) Enter the parameter setting interface for no-load debugging. In the "Controller Parameter Configuration" ->"Operation Mode" option, change "Operation" to "Test". After the change, the controller will not track the main circuit current, and all protection functions will not be activated. However, the control logic is working normally. In this state, you can debug whether the control circuit under no-load conditions is correct. After debugging correctly, please change the "running mode" back to "running". 2) On load debugging   3. The motor starts and stops normally, but the measurement parameters are incorrect. The motor protection controller may malfunction or refuse to operate In the "Operation Data" interface of the display module, it appears that the three-phase current display is 0%; One phase current shows 0%, while the other two phases are normal; The three-phase current display is not 0, but the value differs significantly from the actual current; The voltage and current are correct, but the power and power factor are incorrect. Possible reasons: 1) The built-in transformer plug of the controller is not reliably connected to the main body of the controller; 2) Incorrect setting of motor rated current and CT ratio; 3) The current specification of the controller does not match the motor circuit; 4) Wrong voltage and current phase sequence connection Solution: Check if the built-in transformer is reliably connected to the controller; Correctly set the rated current and CT ratio of the motor (when using an external transformer); Check the voltage and current phase sequence.