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Old August 12th, 2019, 10:14 PM   #1
ceilingwalker
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Trouble matching speeds

Hello. I have a Power Flex 755 that is pulling material (fpm) across conveyor rollers that are controlled by a Powerflex 525 (rpm). I am probably making this way more difficult than it is, Im pretty good at doing that. I am trying to match the speed of rollers to the speed of the material being dragged across them but not sure how to do it. It appears to me as though the feedback from the 755 is actual Hz and the feedback from the 525 is a percentage of nameplate frequency. Any ideas as to how I can match the linear speed of one to the rotational speed of the other? Thank you
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Old August 13th, 2019, 05:47 AM   #2
Lynx777
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If memory serves, the 525 uses Hz as it's speed command and the 755 can be programmed to use Hz, %, or engineering units.
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Old August 13th, 2019, 07:16 AM   #3
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Quote:
Originally Posted by Lynx777 View Post
If memory serves, the 525 uses Hz as it's speed command and the 755 can be programmed to use Hz, %, or engineering units.
You are correct. The reason I couldn't understand my frequency feedback was because someone had the max Hz set to 100, not the Np 60. I didn't check that first!
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Old August 13th, 2019, 08:04 AM   #4
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Another question, please. Why would someone intentionally set max frequency to 100 on a PF525, when its Np value is 60Hz? At first I thought it was accidental however, I have looked at 2 drives this gentleman set up and they are both at 100Hz max. The only thing that makes sense to me is that he might be trying to driving it faster than Np value? That isn't even possible, is it? Its max is 60 Hz, one can't get more out of it than that, right?
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Old August 13th, 2019, 08:14 AM   #5
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Some of the PF drives the default max is set to 130Hz, you can definitely run the motors at higher than the motor name plate Hz, but after that value your torque will drop off.

Alan.
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Old August 13th, 2019, 08:17 AM   #6
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Isnt the 60Hz on the motor name plate for the supply voltage for the motor?

Some use 50Hz and here in the USA we use 60Hz. We have several conveyors with the running Hz set to 70-85Hz in the drives to keep them moving all the time.
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Old August 13th, 2019, 08:24 AM   #7
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I have gone over the nameplate HZ before... if you dont need the torque then its possible, we did it just to stock less motors for backup's

This has some info in it http://www.plctalk.net/qanda/showthread.php?t=66318

There was another thread that I remember from DickDV also but could not find it...
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Old August 13th, 2019, 11:04 AM   #8
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Thanks everyone for the replies about the motor frequency. Anyone have advice how to match the speed of the two drives? The difficulty (for me) is that one is RPM and the other is FPM. I don't know if I should convert the rotary to linear speed and match or just use the rotary speed of both. I just need to make sure the speed of the rollers matches the speed of the material being dragged across them, so the metal doesn't cut the Kevlar sleeves on the rollers. Both motors have gear boxes attached to them so I purchased a handheld device that makes contact with the rotating sprockets and reads rpm as well as fpm, to make my life easier. Lol
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Old August 13th, 2019, 11:31 AM   #9
Lynx777
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For conveyors I like to convert everything to FPM and do the matching from there. Makes it easier to think through.
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Old August 13th, 2019, 11:40 AM   #10
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Quote:
Originally Posted by Lynx777 View Post
For conveyors I like to convert everything to FPM and do the matching from there. Makes it easier to think through.
Thank you
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Old August 13th, 2019, 11:42 AM   #11
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Quote:
Originally Posted by ceilingwalker View Post
Both motors have gear boxes attached to them so I purchased a handheld device that makes contact with the rotating sprockets and reads rpm as well as fpm, to make my life easier
I use to do a lot of work in the 'web' industry and like Lynx777 said convert every to FPM (or sec) worked for me and we always had handheld tachometers to verify the surface or the contact nip rollers
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Old August 13th, 2019, 11:42 AM   #12
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Sorry, I have one more question about exceeding the rated frequency. Add to this the gearbox, which has a max rpm input of 1750. Does it hurt the gearbox if I exceed that parameter? Thank you
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Old August 13th, 2019, 11:47 AM   #13
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Quote:
Originally Posted by ceilingwalker View Post
Sorry, I have one more question about exceeding the rated frequency. Add to this the gearbox, which has a max rpm input of 1750. Does it hurt the gearbox if I exceed that parameter? Thank you
How much?
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Old August 13th, 2019, 11:54 AM   #14
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Sorry, I have one more question about exceeding the rated frequency. Add to this the gearbox, which has a max rpm input of 1750. Does it hurt the gearbox if I exceed that parameter? Thank you
That's a question for the gearbox manufacture. They will want to know the loading and the speed range at a minimum and probably a few other things before giving you an answer.

If your only going a "little" over the rated speed and your "lightly" loaded, they will probably say it's Okay, but they will also say that there is no guarantee.
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Old August 13th, 2019, 12:03 PM   #15
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Quote:
Originally Posted by Lynx777 View Post
If your only going a "little" over the rated speed and your "lightly" loaded, they will probably say it's Okay, but they will also say that there is no guarantee.
I would think they are just like the electrical industry and plus 10% would be OK but anything more than that I would put a thermocouple on the gearbox to watch the temp
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