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Thread: PF4 Locked parameters

  1. #1
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    PF4 Locked parameters

    We set up a system where 2 small VFDs control separate pumps. P1 only runs with A product.
    P2 only runs with B product and neither should run when the other does. A couple years ago we noticed both pumps running. Someone, we thought, had messed with the parameters for the onboard relay which is part or our interlock. We set the parameter again and locked them. Fast forward to yesterday and we have the same problem. Everyone swears, and I believe them, that they didn’t touch. The parameter and only that one had changed,AFAIK. We had to unlock to change it back.

    Anyone with a similar problem with that drive? A solution?
    Tom
    TBLO

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    I have some familiarity with programmable controllers, but not yours in particular...

    Check for any conditions that would change the settings back to as-shipped defaults. But why would that leave your lock intact?? And how would only 1 parameter in your logic be changed?

    Any possibility of the controller reverting to a previously saved version? Perhaps a power glitch makes it re-start the last saved version? Are you sure the changed parameter has been saved as part of the configuration??

    How does your interlock check the 'run' status of the other pump? Any possible glitches there? Although you said there was a changed parameter in the controller.

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    There are two potential issues, but first, are you using the Comm port for making program changes? If not, then one of the issues is not in play.

    Assuming not, the other one is that someone is changing it on purpose and lying about it.

    Unlike all of the other PowerFlex drives, the PF4/40 does not have a password protection feature. So if you set the A101 [Parameter Lock] parameter to (1) to lock it, all someone needs to do to unlock it again is to set A101 back to (0). Anyone who can download and read the manual can do that. The way to control that is to not allow access to the keypad of the drive, i.e. enclose it and put a window on the door to see the display, but not use the key pad unless you have a key to the enclosure door. I've even see people make a little hinged steel strap with a padlock hasp going over the keypad for that purpose. The other solution is to change to the PF523, it has password protection.

    If you ARE using the Comm port to make changes to the programming or send parameters from a PLC, there is potentially another issue. The default programming for the PF4 class drives is for the drive to use the EEPROM as the Non Volatile Storage (NVS) memory and the programming resides there, so the RAM memory that the drive runs from is pulled from the EEPROM every time the drive is powered up. Depending on whether this is a PF4 or 4M (the parameter numbers are different) this is changed in the [Comm Write Mode] parameter. If you make a lot of changes or the drive has power cycled a lot, this setting can exhaust the limited number of write cycles that EEPROM memory is burdened with, it's I think about 10,000 read/write cycles. If you change the [Comm Write Mode] to be to use the RAM directly, the problem is that it will lose that programming every time the power is cycled. So you would ONLY do that if you are "pushing" the drive programming down from a PLC or PC every time power is cycled. If someone changed the [Comm Write Mode] to use RAM and then disconnected the comm port, the drive reverts to Default settings every time power is lost.
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    Ok, small details, I know, I know....

    The PF4 we have that is changing parameters does have a remote HIM. Could there be a conflict as to what is stored in it vs the drive itself? Can someone access those parameters from there? We put it on years ago and haven't delt with another since then.

    A55 is our parameter that is changing.
    Tom
    TBLO

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    So, yes we are using the com port for speed reverence, P038.
    Tom
    TBLO

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    Quote Originally Posted by ptonsparky View Post
    Ok, small details, I know, I know....

    The PF4 we have that is changing parameters does have a remote HIM. Could there be a conflict as to what is stored in it vs the drive itself? Can someone access those parameters from there? We put it on years ago and haven't delt with another since then.

    A55 is our parameter that is changing.
    The PF4 didn't have a DSI port built-in for connecting a remote HIM, so you had to add an RS485-DSI adapter. So that meant that the remote HIM is using the Comm port and the issue I mentioned earlier may be in play.
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    Quote Originally Posted by Jraef View Post
    The PF4 didn't have a DSI port built-in for connecting a remote HIM, so you had to add an RS485-DSI adapter. So that meant that the remote HIM is using the Comm port and the issue I mentioned earlier may be in play.
    I deciphered that to mean there is not much I can do about it and that's good enough. Its all being replaced in some form or fashion in the next couple months which will lead to another thread on how the heck to give a price to someone that does not know what or how they want to do what they think they want done. Logic?
    Tom
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    What I meant is that since it’s is a remote HIM, look at the [Comm Write Mode] parameter to see it’s set to “Ram only”, because that would mean it loses its programming every time power is cycled. If it is, put it back to “EEPROM”.
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    Quote Originally Posted by Jraef View Post
    What I meant is that since it’s is a remote HIM, look at the [Comm Write Mode] parameter to see it’s set to “Ram only”, because that would mean it loses its programming every time power is cycled. If it is, put it back to “EEPROM”.
    I got that part, but it's cycled often enough I don't feel that's happening.
    Tom
    TBLO

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    Quote Originally Posted by ptonsparky View Post
    I deciphered that to mean there is not much I can do about it and that's good enough. Its all being replaced in some form or fashion in the next couple months which will lead to another thread on how the heck to give a price to someone that does not know what or how they want to do what they think they want done. Logic?
    Hummm --
    You just got demoted to "Engineer-of-Record". And the customer needs to have a price before they have a scope. Hopefully you have a good relationship with the customer - if not, well, "yer screwed" (using precise engineering terms - of course)

    Maybe:
    work up a scope for a generic.
    price out material and labor for a PLC with sufficient I/O
    Price out material and labor for a VFD(s)
    Be specific about the material you are providing.
    Be specific any changes to meet their scope changes are extras

    And absolutely charge for your engineering. You probably can't call it "engineering" - but you will think of something to call it that you can bill for.
    Without data you’re just another person with an opinion – Edwards Deming

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