Greetings! I am currently working on fixing a Powerflex 753 (480-600V) unit. After replacing all the optocouplers and IGBT, the VFD is up and running, showing output voltage on the DMM (although this method is not ideal for checking output voltage). However, when I connect the motor, the voltages drop significantly and an under-voltage fault is triggered. It appears to be an issue with the firing mechanism. Can anyone offer guidance on troubleshooting this issue?
It would be advisable to inspect the power bridge rectifier as it appears that some of the rectifiers may be faulty or non-functional. This component plays a crucial role in converting AC to DC power in electronic devices, so it is important to ensure its proper functioning for optimal performance.
Are the motor windings verified to be free from shorts?
Thank you for your responses. I replaced the motor, but the outcome remained unchanged. I also attempted to operate the VFD directly by applying DC voltage to bypass the AC to DC conversion, yet the issue persists.
It may be time to consider replacing your VFD, as you have likely spent too much time already trying to fix it.
Unfortunately, I don't have the luxury of opting out - I need to address this and repair it. Thank you for your assistance.
It seems like you've made good progress in repairing your Powerflex 753 unit. The under-voltage fault triggered when you connect the motor may indicate a problem with the voltage supply to the VFD or a heavy load on the VFD. It could also be due to incorrect parameter settings. I would suggest checking your power supply voltage first to ensure it meets the unit's requirement. Also, try to run the motor at a lower speed or smaller load and see how it responds. Lastly, go through your parameter settings, specifically those related to voltage, and make sure they've been set correctly.
Hello! It seems like your Powerflex 753 might have an issue with load handling. If the voltage is dropping significantly, check the motor connections and ensure they are not loose or corroded, as this could cause a significant voltage loss. Furthermore, consider testing your motor's windings for any signs of insulation failure. Another possible cause could be a problem with your drive's DC bus. A weak capacitor bank may be unable to handle the motor starting impulse, hence leading to an under-voltage fault. Let me know how it goes!
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Answer: 1. Q: What could be causing the under-voltage fault on a Powerflex 753 VFD after replacing optocouplers and IGBT? The dropping voltages and under-voltage fault when connecting the motor may indicate an issue with the firing mechanism.
Answer: Troubleshooting steps may include checking the firing mechanism, verifying motor connections, and ensuring compatibility between the VFD and motor.
Answer: While using a DMM to check output voltage is not ideal, it can provide some indication. Consider consulting the VFD manual for recommended testing procedures.
Answer: Under-voltage faults in VFD units can be caused by issues such as inadequate power supply, motor overload, or problems with the firing mechanism.
Answer: Seek advice on checking the firing mechanism, inspecting motor connections, and ensuring proper setup and compatibility to troubleshoot and resolve the under-voltage fault.
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