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Overheating FK7 servomotors

Created by: DavidBrown at: 9/4/2015 12:01 PM (7 Replies)

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9/4/2015 12:01 PM	Rate (0)
DavidBrown Gold Member Joined: 6/29/2012 Last visit: 12/25/2023 Posts: 975 Rating: (9)	We have several 1FK7 servomotors on S120 that now after 4 years without problems start to give overtemperature faults : F07011 "Motor overtemperature" The temperature of the motor is externally measured as control, and the temperature we see in Starter for the motor is the same as the external control, so the measurement should be ok. The load on the motor is only about 30%. And the environment temperature is not different to the one in the past, when there were not yet overtemperature alarms. We already changed the motor by an unused one (that was bought at the same time of the other motors). We also changed the motormodule. But this gave no result : temperature was again raising to 130°C. Now we are at a stage where do not know anymore what to check. What could be the reason for this high motor temperature?

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9/8/2015 11:49 AM	Rate (0)
Technology Team Platinum Expert Joined: 10/11/2006 Last visit: 10/11/2024 Posts: 5911 Rating: (809)	Dear David, Maybe the load changed due to an increased friction of bearings,... You should verify if the S1-characteristic of the motor is exceeded. Please apply TRACE and record torque, speed and current over a longer period. Compare this data with the characteristic verifying the capability of the motor.
	With best regards, Technology Team Application consulting and pre sales support for SINAMICS, SIMATIC Technology, SIMOTION, SIMOTICS and MOTION CONNECT
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9/8/2015 12:47 PM	Rate (0)
Jeff Casagrande Posts: 1529 Rating: (202)	IF you have an existing system that worked AND suddenly you are getting temperature faults AND you have changed the drive AND you have changed the motor THEN you have a mechanical problem that is causing the motor to overheat. END_IF Trace your current and/or torque to see what is going on. You may also have a bad sensor cable. Is the motor truly going to 130 degrees? That is pretty damn hot.
Jeff Casagrande Posts: 1529 Rating: (202)	Last edited by: Jeff Casagrande at: 9/8/2015 12:49:02 PM Last edited by: Jeff Casagrande at: 9/8/2015 12:50:50 PM Last edited by: Jeff Casagrande at: 9/8/2015 1:00:39 PM
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9/12/2015 11:43 AM	Rate (0)
DavidBrown Gold Member Joined: 6/29/2012 Last visit: 12/25/2023 Posts: 975 Rating: (9)	I did some measurements on the motor and the current is really too low to cause overheating. I also measured surface temperature of the motor and the gearbox. The temperature of the gearbox was higher then the temperature of the motor. My question is : if you have an environment of f.I. 30°C what temperature may the gearbox be for not to overheat the motor? Or is there some kind of value that describes the maximum minimum heat transfer capacity of the gearbox. Or in general : we gave an environment temperature of x°C, the motor is mounted to a steel volume that is continuously at y°C, will the motor overheat or will it be able to find a stable temperature beyond the alarm level?

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9/12/2015 1:26 PM	Rate (0)
Jeff Casagrande Posts: 1529 Rating: (202)	Our gearbox manufacturer (Taiwanese copies of Alpha) gives 90 degrees for shutdown, 70 degrees for operational limits. I set my motor temperature alarms for 80 degrees. The 130 degree default I think is far too high. Your gears may be wearing out. The other thing that may help your gears is to add some Jerk limitation, especially if the operation involves reversing. I have burned out gears within 20 minutes without it and have has the same gear in the same application last (counting) 2+ years with. Gears hate the reversing impact loads.
Jeff Casagrande Posts: 1529 Rating: (202)	Last edited by: Jeff Casagrande at: 9/12/2015 1:28:35 PM Last edited by: Jeff Casagrande at: 9/12/2015 1:56:12 PM
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12/7/2015 11:23 AM	Rate (0)
Ziemens Silver Member Joined: 3/2/2007 Last visit: 10/11/2024 Posts: 938 Rating: (5)	how did you solve this issue?
	... thank you ...
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12/7/2015 11:57 AM	Rate (0)
Jeff Casagrande Posts: 1529 Rating: (202)	Specifically, what is the question?
Jeff Casagrande Posts: 1529 Rating: (202)
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12/7/2015 12:46 PM	Rate (0)
Ziemens Silver Member Joined: 3/2/2007 Last visit: 10/11/2024 Posts: 938 Rating: (5)	how was the problem of F07011 "Motor overtemperature" solved ?
	Last edited by: Ziemens at: 12/7/2015 12:46:49 PM ... thank you ...
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