I got a new project last week, a bailer at a land fill, I know, yuck, its not that bad they keep it pretty clean around the machine, the smell is not that great though, you get use to it after about 30 min. Any way, it has this one 3phase 100amp motor that will trip the main in auto. The operator can get it to produce a bail by toggling a push button a the OCP. I don't know which button it is, I only had 1.5 hrs to look at it and take some measurements Friday. When the operator had to leave I had to leave, so I'll start back on it tomorrow. The first thing I did was log some readings from the PT, which is the only analog instrument on the machine, which usually controls most processes in one way or another, The measurements made me think it was the problem so thats what I spent most of my time on Friday. It only reached 12-14 ma before the machine tried or did trip. There are 4 pressure relief valves on the bailer controlling this motor. 1=1200psi, 2=1200psi,3=1200psi, and 4=1200psi. The two 1200psi are different flow rates or something I forget, I'd have to look it up. Any way my PT reading 12ma so I thought that could be the problem, I thought it should have been 20ma, but when I checked the program the scale w/parameters was set up for max input of 12. So now I'm thinking its prob ally the motor windings, this motor should be 124FLA and its tripping a 400amp main. So I'm thinking there is prob ally a small pin hole in the windings and it doesn't fault out until the motor is pulling a lot of amps, like when 100% pressure is being called for. So thats the first thing I'm checking tomorrow if I can, they might need the machine to run for a while. Any comment welcome.

__________________
DavisIME

One other thing, this program has about 600 lines of code and 8 sub routines, and not the first rung comment in the whole program. Man I hate it when people do that. Thats the first thing they teach you in school, document, document, document. How hard is it to DOCUMENT!!!

__________________
DavisIME

Job security, job security , job security....

I would check a few things.
I have seen simular things happen.
loose conection to the breaker causing thermal tripping.
Instantanious current settings not set properly.
And last a bad breaker.

I think if the motor had bad windings they would have failed completely by now.
Does this only happen on startup of the motor, or is it running steady when it trips?

The breaker I'm talking about is the main breaker from the 1600amp switchboard 40' away. The control panel has a 450amp breaker and the one at the main pnl is a 400amp breaker.
If it was an overload the OL on the starter should trip not the main. Thats what makes me think its the windings.

I've seen situations like this before where the windings have a short and the motor runs fine, untill there is a heavy load on it which draws more amps than normal and the motor trips out. Very hard problem to troubelshoot if you have no knowledge or experiance with this kind of problem. Also if you dont have a megger with enough voltage output it can still drive you crazy. You megg it with 500V it shows no problem, but put 1000V or more through it and there she is. Its one of the reasons I bought the new megger that I did, AEMC 5070 5000V.

__________________
DavisIME

I'm sorry, I see that I didn't answer your question.
This only happens when the baler is in the process of making a bale. Right before the bale should be complete, which is when its at its highest pressure, is when its tries to trip the breaker. The operator has figured a way out to keep the breaker from tripping, which they've been doing for years now apparently, and thats to toggle a push button as he's making the bale. He does this by listening to the sound of the motor, it must be a momentary contact, I didn't get that far like I said a quitting time he and everyone else was out of there, Friday. So I'll be able to check all these items tomorrow.

__________________
DavisIME

i had a similar problem with a bailing machine 2 weeks ago...there is a switch which energies the main solenoid to feed all the cylinders which open and close the bailing press...if that switch is faulty or if the tank return is blocked or not opening it will keep the pressure in the pipes and the motor will stall on startup.

the one i was working on is only manually operated there are no auto functions.

Silly question perhaps but there isn't a shunt trip arrangement on the 400A breaker is there?

Or maybe an e/stop arrangement. I imagine there are some mechanical stresses at that point which may be affecting something seemingly unrelated.

Hey Davis,... Hey Guys...

Interesting problem. Is it possible the accumulative load is at the teter point on the main breaker, and when the motor comes under load it trips the main breaker. Perhaps something was installed by the plant personal putting more load on the circuit.
Another thing I'd look at. Is it possible there is a stuck by-pass valve allowing the pump and motor to become overloaded, and draw excessive current.
Anyway... Good Luck. I'd be real interested in knowing what you find.


Sometimes the old ways are the best.

WORK SAFE!!!!

Glenn D

Sounds like you have plenty of suggestions to choose from. One of the wisest moves is exactly what you have done already....talk to the operator. No one knows the machine like the one that uses it.

Several of the comments would be similar to my suggestions.......I worked on a bailer in the textile plant that bailed the waste material. It was an automatic setup that would startup when the waste material would block an electric eye w/ a reflector. The ram would move back and forth until the "eye" was able to see the reflector. This process would continue until a hydrualic pressure switch would open due to the amount of material being compressed. This signaled the operator to remove the bale. All of the Auto functions could be accomplished in a manual mode too.

I would connect at the tripping breaker with something to log with (I don't know your tool arsenal). It would be interesting to see what the voltage and current were doing just prior to the trip. Especially if you could plot the current....does it ramp to the trip point or hold for some time?

I wonder if this baler works in a similar way to the one I described. If so, in "auto" is there a problem that would prevent the ram from going into reverse to release the pressure? Could this event be avoided when operated in a manual condition??

Just a few thoughts.....

Tom