I was given the task of installing and programming a DG1 VFD model # DG1 34170FN-C21C for a 150hp AHU. Initially, everything was working smoothly, but now we are facing an issue where the VFD stops itself when commanded above 49hz without any faults. The threshold for continuous operation seems to be between 48-49hz. Even when commanded to 60hz, it exceeds 50-52hz and then shuts down. The motor specifications are 150hp, 460v, 167a, and 1.15sf, which are correctly reflected in my parameters. When I check the amp reading, it ranges from 97-113a before it stops. Despite reviewing parameter limits, I am unable to pinpoint the issue and would appreciate any guidance. Thank you for your assistance.
Ensure to review your settings and check the VFD current limit, which should be set around 170 amps. If it's lower than that, it could be entering a current limit mode and experiencing stalling issues. The VFD might be programmed to automatically shut down in case of an overcurrent situation.
Have you attempted running it manually using the keypad? When checking the amperage, readings fluctuate between 97-113 amps depending on when it halts. How are you measuring the amperage? It is not effective to simply attach a clamp on ammeter to the output wiring when dealing with a Variable Speed Drive (VSD).
BryanG inquired: Have you attempted to operate it manually using the keypad? How are you measuring the readings? Simply attaching a clamp on ammeter to the output cabling won't work with a VSD system. This is precisely what I attempted to do... How do you suggest taking readings and why might the VFD hinder accurate measurements on the output? I have tested it in both manual and automatic modes, yielding the same outcome. Despite setting the limit at 192A, the VFD does not fault when it shuts off; rather, it transitions from running to stopping as if it was instructed to halt.
Many contemporary Fluke clamp on ammeters provide accurate readings on VFD output wires, unlike in the past. The VFD prioritizes the output current for current limiting. If the VFD stops despite a run command, check the digital inputs to confirm the RUN bit is active. This may indicate a discrete run signal dropout.
To accurately measure the output current from a VFD, it is important to understand that traditional clamp on amp meters may not be suitable as they are designed for sinusoidal waveforms, whereas VFDs produce a width modulated square wave. The most effective method is to monitor the load output directly from the VFD, either by configuring it to provide an analog output or by viewing it on the VFD display. It is possible that the current being measured is the DC bus current. While there are clamp on meters available that can measure both pure DC and modulated DC currents, it is recommended to explore alternative monitoring options for VFDs.
In my experience, the issue you're experiencing could potentially be due to a high load that your motor is unable to handle, causing the VFD to shut down as a protective measure. I suggest checking the load conditions; alternatively, even though your parameters seem correct, there might be an incorrect setting somewhere causing the VFD to read a false overload. Also, please make sure your motor is correctly rated to handle the required frequency. If your motor's max frequency is below the commanded values, it could cause issues. Just a suggestion, but hope it helps troubleshoot your problem.
Your issue sounds like an overload protection kicking in. One possibility could be that the motor is drawing more current due to a mechanical problem downstream, like a blockage or extra load due to faulty bearing, which affects the motor's performance at higher frequencies. I suggest checking the driven equipment's condition. Also, although it seems you've already reviewed this, do double-check that the parameter settings related to motor protection (like motor thermal capacity and overload setting) are correctly set based on the motor data plate. In some cases, a factory reset then careful drive reprogramming resolves these kinds of issues.
It sounds like you're dealing with a sticky situation. I can't help but consider overheating as a potential issue, especially since the problem happens at higher speeds. Issues like this can stem from the load on the motor being too high for the VFD, causing the VFD internal temperature to rise quickly until the unit goes to self-protect mode. Perhaps, you could try to monitor the temperature inside the VFD next time you test it. If this seems to be the case, you may need better ventilation or even an external cooling system to enhance the heat dissipation. Otherwise, you might want to consult with the manufacturer directly as their technicians could have run into similar issues in the past.
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Answer: - The VFD may be stopping itself due to the frequency exceeding 49hz without any faults. Check the parameter settings and ensure they are correctly configured for the motor specifications.
Answer: - The VFD might be exceeding 50-52hz when commanded to 60hz, leading to it shutting down. Review the parameter limits and ensure they are set appropriately for the motor's requirements.
Answer: - Troubleshoot by checking the amp readings, verifying the parameter settings, and ensuring they align with the motor specifications of 150hp, 460v, 167a, and 1.15sf. It could help in identifying the root cause of the problem.
Answer: - Verify the VFD parameter settings, inspect the motor specifications, and consider consulting the VFD's manual for troubleshooting guidance. It might help in resolving the issue of the VFD stopping when the frequency exceeds 49hz.
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