First, the keyboard does not display after the electric: 1. Check if the input power is normal. If it's normal, measure the voltage at 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, try replacing the keyboard and its cable. If the display still doesn’t work, check if the 26P cable connecting the main control board and the power supply board is loose or broken. 3. If the switching power supply works normally after power-on, the relay makes a pickup sound, and the fan runs properly, but the display is still blank, this could indicate a faulty crystal oscillator or resonant capacitor on the keyboard. In that case, consider replacing or repairing the keyboard. 4. If everything seems normal after power-on, but the display remains off, the switching power supply may be malfunctioning. Unplug the P and N supplies, then check the static voltage of IC3845 (use experience to determine). If IC3845 is okay, apply power again and check if the 8V/1W Zener diode shows about 8V. If the switching power supply still doesn't work, check the secondary side rectifier diodes for breakdown or short circuits. 5. After power-on, if the 18V/1W Zener diode has voltage but the display is still off, remove external cables such as the relay and fan lines, and check if the fan or relay is shorted. 6. When the P and N terminals are powered, the voltage across the 18V/1W Zener diode is about 8V. Use an oscilloscope to check if pin 4 of IC3845 has a sawtooth wave and if pin 6 has output. 7. Check the output of the switching power supply (+5V, ±15V, +24V) and ensure there is no short between the ground and the power supply. Second, the keyboard display is normal, but the device cannot operate: 1. If the display is normal but the function keys don’t respond, check if the keyboard is compatible with the main control board (e.g., whether IC75179 is included). For systems with internal and external keyboards, verify the DIP switch settings. 2. If only some buttons don’t work, check if the microswitches on those buttons are faulty. Third, the potentiometer cannot be adjusted: 1. First, confirm that the control mode is correctly set. 2. Ensure the signal selection and analog input parameters are properly configured. 3. Check that the main control board’s DIP switches are set correctly. 4. If all settings are correct, the potentiometer itself might be faulty. Test its resistance to see if it’s within the expected range. Fourth, overcurrent protection (OC): 1. When “FO OC†is displayed on the keypad, “OC†flashes. Press “∧†to enter fault inquiry mode and check the running frequency, output current, and status. Determine if the “OC†is due to overload or Vce protection (short circuit, drive failure, or interference). 2. If the current increases during acceleration due to heavy load, adjust the acceleration time and V/F curve accordingly. 3. If the motor isn’t connected, the inverter may skip the “OC†protection. Turn off the power and check for IGBT damage. Also, test the junction capacitor between the IGBT’s freewheeling diode and GE. If it’s good, check the drive circuit: - Ensure the drive line is properly connected and not loose. - Check for HALL sensor or wiring faults. - Inspect amplification components like IC33153 or optocouplers for shorts. - Check the drive resistor for open circuits, shorts, or resistance changes. 4. If “OC†occurs during operation, check if the motor is jammed, causing sudden current spikes. 5. If “OC†appears 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, press “∧†to check the running frequency, output current, and status. If the current is too high, the load may be too heavy. Adjust acceleration/deceleration time, V/F curve, and torque boost. If the problem persists, reduce the load or use a larger inverter. 2. If the output current is normal, check the electronic thermal overload relay parameters. 3. Verify 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 for continuity. If it’s disconnected, the temperature switch may be faulty. 2. A faulty fan can cause overheating. 3. High ambient temperature or poor ventilation can lead to internal overheating. 4. For inverters with seven-unit IGBTs, temperature detection uses the thermistor inside the IGBT. If “OH†occurs, possible causes include: - Faulty comparator with high output. - Comparator compares a lower resistance value than the reference. - Abnormal resistance in the IGBT’s thermistor. Seventh, overvoltage protection (OU): 1. Overvoltage during deceleration is often caused by high inertia loads. Extend the deceleration time, or add a braking unit and resistor to dissipate energy. 2. Adjust the VpN parameter if overvoltage occurs after replacing the power or main control board. 3. If the input voltage exceeds the inverter’s rated voltage, overvoltage may occur. Eighth, undervoltage protection (LU): 1. First, check if the input voltage is stable and the wiring is intact. 2. Ensure the “04†parameter is set correctly. 3. Adjust the VpN parameter if undervoltage occurs after replacing the power or main control board. 4. Poor performance of devices like op-amps in the voltage detection loop can also trigger undervoltage. Ninth, frequency display exists but no voltage output: 1. After the inverter starts, if there is a frequency but no U/V/W output, check if the carrier frequency parameter is lost. 2. If the parameter is normal, run the inverter and check the drive waveform using an oscilloscope. 3. If the waveform is abnormal, check if the SPWM signal from the main control board’s CPU is normal. If it’s faulty, replace the CPU. If the SPWM is normal, try replacing the 26P cable. If the issue persists, the driver circuit may be faulty and needs repair or replacement. Tenth, the relay does not pick up: 1. First, check if the input power is normal. 2. Ensure the connection between the power board and the capacitor board is secure. 3. Check if the 26P cable between the main control board and the power supply board is loose or disconnected, which may prevent the REC signal from being sent. 4. A faulty relay pull-in circuit can also cause this issue. 5. The relay itself may be damaged (e.g., coil open).
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