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Field Standstill is not functioning properly for 6RA70

Created by: Timmy at: 5/10/2012 9:28 PM (7 Replies)

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5/10/2012 9:28 PM	Rate (0)
Timmy Posts: 41 Rating: (0)	The motor is used in a stop start application as part of a flying shear. The motor acclerates the shear to line speed to make a cut and then parks the shear using postion control. The drive does have a T400 that it uses to switch to and from speed and position control as needed. We have burnt up a coupld of motors and after the second one we discovered that we are cooking the fields. We then went back into the program to verify that the field standstill or economizing mode was setup for the motor drive. It is with P082 = 2 P257 = 10% P258 = 20s I then hooked up a data recorder to the field circuit to get the actual field current while the motor is running and it is never going into a reduced field state. So I looked into the book and was able to verify that the drive is in the right operating state (above 7.0) and everything else made sense for it to be enabled but could not find out how the time starts timing. It just says motor stopped. Does that mean that the speed feedback is 0? What if the tach signal blips every so slightly? Also, what if the motor is in a position control operation instead of speed control? I also noticed that I can set the drive to economize by linking something to P0692. Has anybody done this and have any useful tips or signals to override the P257 and P258 method? Thanks in advance and if more information is needed I will be happy to supply.
Timmy Posts: 41 Rating: (0)	Last edited by: Timmy at: 5/10/2012 9:28 PM
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5/11/2012 4:39 AM	Rate (0)
KSN Platinum Expert Joined: 8/25/2006 Last visit: 9/11/2025 Posts: 2218 Rating: (282)	Hello. Operating state above 7.0 is the state when main contactor is opened, so I think this never works in shear application. What about cooling of motor? Is the field current not higher then rated current during work? From where field current setpoint comes? Check the field current setpoint and actual value during work. And tell the drive order number.

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5/11/2012 7:57 AM	Rate (0)
Shahide043 Posts: 57 Rating: (0)	Hi, Have u configured the parameter no : P076 according to the name plate on the motor?
Shahide043 Posts: 57 Rating: (0)
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5/11/2012 5:22 PM	Rate (0)
Timmy Posts: 41 Rating: (0)	The drive is 6RA7087-6FV62-0 Ratings 460V, 850A arm, 460V, 30A field Motor is 200 hp DC Leroy Somer 1000RPM base 500V, 330A armature 8.95 A field P76 is setting the drive paramters down to 66.6% for armature and 60% for field so after those settings the drive is derated to 566A armature and 18A field The cooling of the motor is via an external blower using filtered ambient air. Which does seem to be working (no clogged filter, filter changed every month, flow is correct direction, etc...) The field weakening mode is disabled with a max process setpoint of around 850rpm. This speed setpoint is generated from the line speed of the machine. So, for this application we will always be below base speed and thus at full field under operation so the setpoint shouldn't change.... Underload or during operation the field fluctates up and down around the rated field current but I cannot determine if it is the fluke clamp meter or the actual field. I will change one of the analog outputs to field current and compare to the clamp on readings so I can give you a spread of the variation when the shear moves. This is the first time for me exploring how this is done in a 6RA70 so I am trying to see how they were going about doing this and why it is not working. Thanks if you need more information I will get it.
Timmy Posts: 41 Rating: (0)
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5/11/2012 6:06 PM	Rate (0)
KSN Platinum Expert Joined: 8/25/2006 Last visit: 9/11/2025 Posts: 2218 Rating: (282)	Hello. Did you make optimisation runs (especially for armature and field current controllers) of the drive and complete start-up procedure described in themanual, chapter 7.5.

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5/16/2012 3:13 PM	Rate (0)
Timmy Posts: 41 Rating: (0)	KSN, The actual field current sent out via an analog output looke to be flucating between 99.8 to 103%. The drive was installed by the Siemens Metals group and they did all the tuning. I would say they did it manually. Since changing the motor I have NOT performed a field tuning or any of the other available tunes. Now, I would like to correct myself from one of my statements above. Inbetween cuts or during long periods of down time the drive is not going into a state above 7.0 (sorry for the confusion) The drive is staying in low operating state with the main contactor closed. The holding brake is not engaging until two minutes of no product via a plc output and not an output from the drive. So, what I would like to do is piggyback the holding brake output from the PLC as a signal to the drive to go into the field weakening state. It looks like I just need to run a output from the PLC to an input on the drive and then setup the P692 to look at that input. Thus, I will be going into a field weakend state when the holding brake is engaged and when I need to run or sense product coming I will release brake and go back to 100% field. Should I have any concern about going to a reduced field state with the main contactor remaining closed? Also, right now it is setup to go to 10% field current while most of the other dc motors in the area are going to a 25% field current fro standstill. Is there a rule of thumb here or does it matter? Thank you for all your help.
Timmy Posts: 41 Rating: (0)
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5/16/2012 4:01 PM	Rate (0)
KSN Platinum Expert Joined: 8/25/2006 Last visit: 9/11/2025 Posts: 2218 Rating: (282)	Hello. I'm not sure is it permissible to reduce the field when main contactor is closed for such a drive like flying shear. Why you have not done optimization runs after changing motor?

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5/16/2012 9:03 PM	Rate (0)
Timmy Posts: 41 Rating: (0)	It is not common practice for us to do motor tuning if we are changing the motor out with another exact spare. Now, if this were another application I would do the tuning, however, the specialized manual tuning has me a little nervous messing with it.....I see the different tests from the manual which ones would you suggest?
Timmy Posts: 41 Rating: (0)	Last edited by: Timmy at: 5/16/2012 9:10 PM As far as the flying shear application with the holding brake engaged I do not have much of a problem with reducing the field via a PLC because the PLC is the cut command master to the system so I can limit/delay a cut command based on a set time for the field to be back to 100% and the brake to be released. If you know of a specific reason NOT to do it please let me know.
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