5/03 analog scaleing

[DavisIMI 0]

I'm in the process of troubleshooting a bailer, the 100amp hyd. pump keeps tripping the main breaker, I first checked the PT, which is the only analog device on the machine, I was logging measurements off of the PT and noticed it was only maxing out a 12ma, so I thought something was wrong with the PT, out of calibration or something, untill I found in the program the scale w/parameters instruction and the input max is set to 12000. ?? I was thinking I would find 20000, is this a normal setup? To me that means the PT is inputing the correct pressure input. I only had time last Friday to take this one logging session, more test will be run this week. I just wanted to ask if this is normal. One more thing, this program has 600 lines of code and 5 subroutines and not the first word of any rung comments in the whole program. I hate it when that happens.

[lccllc 0]

Is this a three phase pump, if so have you metered the motor with an meter and a megger, this will tell you alot about the windings of the motor. Is the motor tripping the breaker or is the plc tripping it due to overcurrent via a shunt or 0 volt coil, or it the plc using this scale for display.

[DavisIMI 0]

No, like I said I only had time to take some reading last Friday of the PT, which was the first thing I tested, I plan on doing test with the megger tomorrow. The operator gets the bailer to work by running it in manual and toggling a button to keep the breaker from tripping. As I've had a chance to think about it this weekend, I think it is the motor windings because its a 100hp 3phase motor, FLA should be around 124amps according to my little calculator, and its tripping a 400amp main, so to me, its should be the motor windings. I have a AEMC 5070 5000V megger so It should be able to find the problem. I also received Friday the operators manual to read this weekend, I found out at the operator station they have a little HMI where they can change the materials, like a recipe, so that could be the problem, which it shouldn't be tripping the 400amp main. It's hard to tell the dang program has no document ion whatsoever, hard to follow. I've been going through it and trying to document what I think is going on to help in troubleshooting later this week. On paper of course, I'm not messing with the program at all. It's been working for years, heck I put the machine in back in 2001, but its been having this tripping problem for a while now, nobody else wanted to mess with it and I just went in to business last year, so its my first shot at this problem.

[Guest]

Greetings DavisIMI ... and welcome to the forum ... it seems that your major question right now is about the "Input Max" setting on the SCP ... we can't tell whether this is "right" for your system without knowing more about how everything is set up – but here's something that MIGHT be helpful ... the "Input Max" setting does NOT (I repeat: does NOT) mean the "highest/maximum input signal that should ever come in" ... instead it just helps set up a ratio between the INPUT signal and the SCALED signal ... specifically, you don't have to use the MAX/HIGHEST value for the input signal – you just need a value that CORRESPONDS with whatever value that you enter for the "Scaled Max" setting ... more specifically, the SCP does NOT perform any type of "limiting" function ... in other words, if the actual input signal happens to go higher than the "Input Max" value that you entered, then the output value will simply GO HIGHER than whatever "Scaled Max" setting you entered ... so ... it's entirely possible that the numbers you've reported are OK for your system – just as long as the "Input Max" entry correctly corresponds with the "Scaled Max" entry - and likewise, that the "Input Min" entry correctly corresponds with the "Scaled Min" entry ... incidentally, I've seen a least one popular "text book" (not an official Allen-Bradley publication) that misinterpreted the meaning of "Max" and "Min" ... so be careful if you're basing your troubleshooting on something like that ... not all books are correct ... anyway, I know that this sounds like it's going in circles – but if you can post your .RSS program, we'll be glad to go through it and nail everything down for you ... incidentally, if you're interested, you can find a lot more about "scaling" by downloading the "Scaling with y=mx+b" material from the Sample Lessons page on my website ... it's in two parts so download them both ... as far as the "rung comments" issue, you might want to take a look under "View / Properties / Comment Display" from the RSLogix500 main menu and make sure that the "Rung Comments" feature is turned on ... some people turn it off to save room on the screen ... years ago I actually drove 120 miles (one way) to help a new programmer debug a piece of used equipment that his company had just bought ... when I got there he was fussing and fuming because there weren't any rung comments in the existing program ... he went ballistic when I clicked the magic spot and the comments popped up all over the screen ... hope this helps ... good luck with your project ...

[DavisIMI 0]

I have the program saved on my laptop, I opened it up and I clicked view and it didn't give a properties option.?? Maybe I need to be on line with the processor? Edited 13 Jul 2009 by DavisIMI

[DavisIMI 0]

Also Ron, I plan on attending you PLC Boot Camp but right now the way business and the economy is I really can't appropriate the funds, which means I don't have that kind of money right now to spend on training, although I'm sure its worth every penny. Hopefully within next year.

[DavisIMI 0]

Here is the file.5054.RSS

[DavisIMI 0]

Ron, Thanks for the tip on the scaler pdf. I downloaded them both and a great read. Do you have any such info or could you direct me to a post that has info of the like on programming say a PT controlling a FCV and a VFD or something to that nature. I know how it all works, I just don't understand how to implement that into a program. Any info will be greatly appreciated. Thanks