Inverter pulse circuit fault detection - Solutions - Huaqiang Electronic Network

Brand AVX TPSE226M035R0125 Low impedance tantalum capacitor AVX 22

Filter 18.432M

The inverter pulse circuit consists of two parts: the pre-stage circuit, which connects the six PWM output terminals of the CPU to the intermediate buffer, and the post-stage drive circuit. Together, they form the complete inverter pulse system. Understanding this structure is crucial for troubleshooting. Fault conditions may include:

1. Normal start-up and frequency display, but no three-phase output voltage.
2. Normal start-up and frequency display, but unbalanced three-phase output voltage.
3. OC fault occurs when the start button is pressed.
4. OC fault appears during operation.
5. Light load operates normally, but under full load, the motor stutters or triggers an OC fault.
Understanding the root causes and how to approach repairs is essential:

For condition 1, possible causes include loss of +5V power supply to the optocoupler, damage to the pre-stage buffer, unstable control signals from the CPU, or a malfunctioning protection circuit that locks the pulse signal. It's important to note that the pre-stage circuit can be directly controlled by detection circuits. A faulty protection system might block all pulse signals, making it difficult to trace the issue.

In condition 2, issues could involve a damaged optocoupler, high internal resistance in the inverter module, or defects in the pre-stage circuit or CPU output pins. These problems often lead to missing pulses, which can be tricky to diagnose without careful inspection.

Condition 3 may stem from a faulty drive circuit or insufficient power supply capacity, such as a failed filter capacitor or inefficient rectifier diode. Even if static tests appear normal, dynamic current output should be checked thoroughly.

For condition 4, factors like poor drive circuit performance, inaccurate current detection, or reference voltage drift in the fault detection system can cause false OC faults. Additionally, user-related load issues must not be overlooked, as they can also trigger similar symptoms.

Finally, condition 5 might indicate inadequate drive circuit output, a defective inverter module, or issues with the motor itself. Sometimes, the problem lies outside the inverter, such as a faulty motor. It’s always a good idea to test with a different motor to rule out external factors.

Overall, diagnosing these faults requires a systematic approach, combining both electrical testing and logical analysis. Paying attention to subtle signs and considering all potential causes will help identify the true source of the problem.