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drew_1518

F700 series vfd won't speed up.

6 posts in this topic

Need help asap. I have a F700 series vfd on a rainbird pump station. 50hp, 60Hz, 480VAC. It was running fine, then we had to depressurize the station to add a new chlorine line. Turned it all on, pressured the station back up & that's where weird bug came in. VFD will kick on (on auto) and ramp up to 37Hz then drop to 33Hz for 10-20sec and shut off. Does not through & errors or alarms. Went through parameters with Mitsubishi engineer twice & everything is correct. Any ideas?

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Please describe how the drive is commanded to start. Is it from a plc, pushbutton, network connection? If it is controlled by a plc or other controller, is the drive being commanded to stop? Sometimes we monitor the current feedback from the drive and will command the drive to stop if current is above a programmed set point for a certain amount of time.

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It is being commanded by a PLC via a HOA switch. It's a Mitsubishi FX3u-16M PLC with a mitsubishi GOT1000 HMI. No errors on the plc or vfd & no alarms on the HMI screen.

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Have you tried to run in in fully manual mode (start it via the buttons on the inverter) - disconnect the PLC and everything, and just use the buttons on the VFD... Is that a possibility to test out?

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Ok, found the problem. Discharge gauge & press transducer are off by about 40psi. Gauge is stuck & transducer is malfunctioning. Showing 30psi at a true reading of 0psi. Was able to adjust the offset & gain on the analog input module just enough to run the station until new transducer arrives. So, bc my transducer was showing 110 psi & my actual running pressure was only about 70psi & was causing the vfd to "run over the allowable pressure limit" for the set time. This was causing my vfd to think that the vfd to think that there wasn't enough demand to keep the big pump running, even on the biggest station. Thanks for the input guys.

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No problem, glad you got it running!

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