Fault Analysis:
The Lenze 8215E inverter's panel information appears normal, yet there is no output. While the panel display is functional, this suggests that the onboard switching power supply and the CPU on the mainboard are operating correctly. The primary reasons for the lack of output from the inverter include:
1. The input voltage may be below the allowable threshold, keeping the output disabled.
2. The output frequency might be set to zero.
3. Internal component failure could block the output. Addressing these issues requires a comprehensive approach, taking into account various factors and following a logical troubleshooting sequence.
Troubleshooting:
The three-phase AC supply voltage measures approximately 385V, confirming that the power supply is stable. The absence of the LU warning on the panel verifies that the inverter’s main power supply voltage is adequate. Additionally, the DC bus voltage inside the unit meets the required specifications, suggesting that the power frequency rectifier bridge and filter capacitors are functioning correctly. Testing the inverter’s output terminals U, V, and W without power using a multimeter confirms no diode effect between +UG (DC bus terminal) and -UG (DC ground), indicating that the inverter module's main circuit is intact.
Focusing on the driver board’s gate drive circuit, including the inverter module’s six-bridge arm power supply voltage and drive signals from the motherboard, is crucial. After opening the inverter housing, removing the filter board and motherboard, and isolating the driver board, we verified the necessary conditions for the inverter module to operate. Each bridge arm power supply’s normal output voltage was confirmed, with the +12V generated by the inverter’s switching power supply supplying power to each bridge arm’s gate power supply.
The inverter module’s switching power supply operates by rectifying the three-phase AC voltage and filtering the resulting DC bus voltage, which is then input via X3N and X5N terminals. The excitation of V100 by HYB001 generates oscillation, and different windings of T100 produce the required DC voltages for the inverter (e.g., +12V). The unique power supply characteristics of the Lenze 8215E inverter’s module prevent electromagnetic coupling between multiple coils, reducing interference and enhancing overall reliability. The indirect RC components at V107’s 5,6-pin generate self-oscillation, creating a 1MHz square wave signal for the DC conversion circuit. V108 and V109 enhance the current drive capability of the subsequent stages, while V102 and V103 form a push-pull circuit driving T101, T103, and T104. V200 and V219 drive T102.
Given the sensitivity of the inverter module to static electricity, the inverter module must be handled carefully during maintenance. Reconnecting the cable between the driver board and motherboard ensures proper communication. External power sources, including an isolation transformer, three-phase autotransformer, rectifier, and filter circuit, are fed into the driver board via X3N and X5N terminals. For safety, adjusting the autotransformer’s output voltage provides a controlled DC voltage range to the driver board. When the mainboard’s red indicator light begins flashing, it signifies the internal switching power supply has initiated, with all DC voltages being output and the mainboard operational. Using a multimeter, the collector voltage of V102 and V200 measures +12V, confirming normal power supply.
However, measuring the six-channel gate power supply voltage revealed abnormal readings: the three-phase gate power supply voltage for the upper arm was about 8V (normal), while the three-phase gate power supply voltage for the lower arm was 0V (abnormal). Observing the upper and lower arm gate power circuits’ similarities, the signal flow direction was analyzed using an oscilloscope. V108 and V109’s input terminals displayed similar signal waveforms, but their outputs varied significantly. V108’s output exhibited an inverse relationship with its input signal, while V109’s output voltage remained nearly constant at 0V. Possible causes included:
1. V109 short-circuiting.
2. V200 or V219 short-circuiting to ground.
Using a heat gun, V109 was removed from the board for testing. Pin 6 of its output was found to be shorted to ground. As V109 is paralleled in each circuit, a single short-to-ground in any circuit impacts the entire output. V200 and V219 showed no anomalies.
Replacing V109 restored normal functionality, with the lower arm’s three-phase gate power supply voltage functioning correctly. Reinstalling all components, connecting the inverter to three-phase AC, and testing the entire system confirmed the machine returned to normal operation.
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