First, the keyboard does not display after the power is turned on: 1. Check if the input power supply is normal. If it is, measure the voltage between the DC bus P and N terminals. If there is no voltage, turn off the power and check if the charging resistor is damaged. 2. If the P and N terminal voltages are normal, replace the keyboard and its connecting cable. If the issue persists, check if the 26P cable connected to the main control board and the power supply board is loose or broken. 3. If the switching power supply operates normally, the relay makes a clicking sound, and the fan runs properly, but the keyboard still has no display, this may indicate a faulty crystal oscillator or resonant capacitor in the keyboard. At this point, the keyboard should be replaced or repaired. 4. If everything appears normal after powering on, but the display is still blank, the switching power supply might not be working. After turning off the power, unplug the P and N power supplies and check the static voltage of IC3845 (using experience). If the IC3845 is functioning correctly, apply power again and check if the 8V/1W Zener diode reads around 8V. If the switching power supply still doesn't work, check if the secondary-side rectifier diode of the switch transformer is shorted or damaged. 5. If the 18V/1W Zener diode shows voltage after power-on, but the display is still blank, remove external plug-in lines such as the relay and fan cables, and check for any short circuits in the fan or relay. 6. After power is applied to the P and N terminals, the 18V/1W Zener diode should show about 8V. Use an oscilloscope to check if pin 4 of IC3845 has a sawtooth waveform and if pin 6 has an output signal. 7. Check the outputs of the switching power supply (+5V, ±15V, +24V) and ensure there is no short circuit between the ground and the power supply. Second, the keyboard display is normal, but the functions cannot be operated: 1. If the keyboard display is normal, but the function keys do not respond, verify that the keyboard and main control board are compatible (check if IC75179 is present). For systems with internal and external keyboards, check the DIP switch settings to ensure they are correct. 2. If only some buttons are unresponsive, the microswitches on those buttons may be faulty. Third, the potentiometer cannot be adjusted: 1. First, confirm that the control method is set correctly. 2. Check if the given signal selection and analog input mode parameters are properly configured. 3. Ensure the DIP switch settings on the main control board are correct. 4. If all previous checks are correct, the potentiometer itself may be defective. Test its resistance value to see if it is within the expected range. Fourth, overcurrent protection (OC): 1. When “FO OC†is displayed on the inverter keypad and “OC†flashes, press “∧†to enter fault inquiry mode. This will show the running frequency, output current, and operating status. Based on this data, determine whether the “OC†protection is due to overload, Vce protection (short circuit or drive failure), or interference. 2. If the current increases during acceleration due to a heavy load, adjust the acceleration time and the V/F curve accordingly. 3. If the motor is disconnected, the inverter may bypass the “OC†protection. Turn off the power and check for IGBT damage. Also, inspect the junction capacitor of the IGBT’s freewheeling diode for faults. If it is okay, check the drive circuit: - Ensure the drive line is properly connected and not loose. - Check if the HALL sensor or wiring is faulty. - Inspect amplification components like IC33153 or optocouplers for shorts. - Check the drive resistor for open circuits, short circuits, or variable resistance. 4. If “OC†occurs during operation, check if the motor is jammed, causing excessive current due to sudden load changes. 5. If “OC†happens during deceleration, adjust the deceleration time and mode based on the load type and weight. Fifth, overload protection (OL): 1. When “FO OL†is displayed and “OL†flashes, press “∧†to view the fault details. Check the running frequency, output current, and operating status. If the output current is too high, the load may be too heavy. Adjust acceleration/deceleration times, V/F curve, and torque boost settings. If the problem persists, consider reducing the load or upgrading to a larger inverter. 2. If the output current is normal when checking the fault, verify that the electronic thermal overload relay parameters are set correctly. 3. Check the HALL sensor and wiring for faults. Sixth, overheat protection (OH): 1. Check if the temperature switch wire is properly connected. Use a multimeter to test if the wire is open. If so, the temperature switch or wiring may be faulty. 2. A faulty fan can also trigger overheat protection. 3. High ambient temperatures or poor heat dissipation can cause internal overheating, leading to OH protection. 4. For inverters using seven-unit IGBTs with rectifier bridges, temperature detection is done via the thermistor inside the IGBT. If OH occurs, possible causes include: - Faulty comparator with high output. - Comparator compares lower resistance than expected. - Abnormal resistance in the IGBT’s internal thermistor. Seventh, overvoltage protection (OU): 1. Overvoltage during deceleration is often caused by high inertia loads. Extend the deceleration time. If the issue remains, add a braking unit and resistor to dissipate energy. 2. Adjust the VpN parameter resistance if overvoltage is caused by replacing the power supply or main control board. 3. If the input voltage exceeds the inverter's rated voltage, overvoltage can occur. Eighth, undervoltage protection (LU): 1. First, check if the input power is stable, the wiring is intact, and there are no missing phases. 2. Verify that the “04†parameter resistance is set correctly. 3. Adjust the VpN parameter resistance if undervoltage is due to replacing the power board or main control board. 4. Poor performance of devices like op-amps in the voltage detection loop can also cause undervoltage. Ninth, frequency display exists but no voltage output: 1. After the inverter starts, if frequency is shown but no voltage is output across U, V, W, check if the carrier frequency parameter is lost. 2. If the carrier frequency is normal, run the inverter and use an oscilloscope to check the drive waveform. 3. If the drive waveform is abnormal, check if the SPWM signal from the main control board's CPU is normal. If it is not, the CPU may be faulty. If the SPWM signal is normal, try replacing the 26P cable. If the drive waveform is still abnormal, the driver circuit may need repair or replacement. Tenth, the relay does not engage: 1. First, check if the input power is normal. 2. Ensure the connection between the power board and capacitor board is secure. 3. Check the 26P cable between the main control board and power supply board for poor contact or disconnection, which could prevent the REC control signal from being sent. 4. A faulty relay engagement circuit can also prevent the relay from picking up. 5. The relay itself may be damaged (e.g., coil open circuit).
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