Motor OC protection

[ptonsparky]

I get data from a PLC system I set up years ago that is sent to me about midnight each night. I made changes to portions of the logic a week ago so I am looking at it each morning.

I noticed this morning that a 60 HP motor ran at 153.699 amps for just over 11 minutes. My arbitrary shut down via logic is > or = to 154 @ 5 seconds. Yes, twice the NEC FLA for a 60HP. No, it was not part of my recent change but it will be soon. Probably some sort of sliding scale. Normally run is 30-35 A.

Where the operator was, IDK. Restroom break? I haven't talked to them yet.

Shouldn't the motor overloads have tripped sometime in that 11 minutes? I do have PFC at the motor and we do reduce the OLs accordingly.

IDK if it was the operator or overloads, but it did shutdown for about 15 seconds before being restarted to run normally again.

 

[ptonsparky]

Well, motor overloads did trip and everything did shut down as needed. My logic locked in the 153.699 Amp reading until he restarted. I will fix it.

Sorry for the panic attack.

 

[Dzboyce]

Well at least the high amps weren’t from the operator getting sliced and diced.

 

[Cow]

What does the motor run?

 

[Dzboyce]

Sounds to me like whatever the motor runs got plugged up. Took that long for the operator to wake up and notice it. Does the operator know you get thst daily report?

 

[ptonsparky]

Looking at things more closely now that I’ve talked to the operator, my logic shut things down before the overloads had time to trip.

Motor normally runs 30-35 amps. Operator was in a front end loader moving finished product. Normally they stop the feed before leaving the building but not this time. Operator error?

 

[ptonsparky]

Sounds to me like whatever the motor runs got plugged up. Took that long for the operator to wake up and notice it. Does the operator know you get thst daily report?

Yes, he knows and I try not to be a PI rear. H knows how to disconnect the web connection if I am.

 

[Tony S]

Where the operator was, IDK. Restroom break? I haven't talked to them yet.

Best of luck, many moons ago I wrote a program for a transportation system. The first operator on the line had to measure the hot casting and press just one button to let it continue on its journey or be scrapped. According the process management my program was cr@p, they weren’t happy when I showed them a photograph of the operator fast asleep.

Other incidents happened (one a close fatality) and so I was well and truly p****d off. End result, 750 8 bit registers used just to monitor the one operator station. The management didn’t know I’d put it in there.

Operator error was the bain of my life!

 

[ptonsparky]

Best of luck, many moons ago I wrote a program for a transportation system. The first operator on the line had to measure the hot casting and press just one button to let it continue on its journey or be scrapped. According the process management my program was cr@p, they weren’t happy when I showed them a photograph of the operator fast asleep.

Other incidents happened (one a close fatality) and so I was well and truly p****d off. End result, 750 8 bit registers used just to monitor the one operator station. The management didn’t know I’d put it in there.

Operator error was the bain of my life!

The operators I deal.with here do care. Doesn't mean there isn't an occasional error.

 

[drktmplr12]

The operators I deal.with here do care. Doesn't mean there isn't an occasional error.

its a beautiful thing when o&m and engineering have mutual respect. its too bad that in many industries there is this notion from the engineering side that somehow operators are most often to blame for problems and from the operator side engineers don't know a darn thing about how things actually work. :slaphead:

 

[kwired]

its a beautiful thing when o&m and engineering have mutual respect. its too bad that in many industries there is this notion from the engineering side that somehow operators are most often to blame for problems and from the operator side engineers don't know a darn thing about how things actually work. :slaphead:

The problem is each side has different goals. Engineers didn't design things for what the operators want it to do.

Then comes in the owner and the fact they didn't want to spend extra $$ on something, though they want more production out of what they got than it was designed for.

Was setting up ammeter on a brand new grain elevator leg (so operator can tell when it is near full rating and adjust the product feed accordingly). Owner happened to be there when running one of the first loads and says "we need to be able to unload trucks faster than that". Wanted to say then you should have spent the money on something larger, which possibly was an option but he chose this one. I just told him that if you go more you are overloading that motor and it will shorten it's life.

 

[Tony S]

From an article I wrote many years ago.

"In a production environment you will soon discover everything is an electrical fault. A conveyor motor won’t run, the overloads must be faulty! It’s got nothing to do with the tonnes of spillage burying the conveyor and the overloads are doing their job protecting the motor."

 

[Jraef]

From an article I wrote many years ago.

"In a production environment you will soon discover everything is an electrical fault. A conveyor motor won’t run, the overloads must be faulty! It’s got nothing to do with the tonnes of spillage burying the conveyor and the overloads are doing their job protecting the motor."

When I’ve said such things I’ve been accused of being too cynical. But the reality is, it’s all too true...

Last week I got a complaint that some overloads we supplied are all defective, because one kept tripping, so they replaced it and the replacement kept tripping, so they repeated that again. Must be a batch of defective OL relays I guess. Oh and what was the current reading when it tripped?

“I don’t know, we didn’t measure it. But the motor didn’t feel hot at all, I could put my hand on it.”

Uh huh...

 

[Cow]

The problem is each side has different goals. Engineers didn't design things for what the operators want it to do.

Then comes in the owner and the fact they didn't want to spend extra $$ on something, though they want more production out of what they got than it was designed for.

Was setting up ammeter on a brand new grain elevator leg (so operator can tell when it is near full rating and adjust the product feed accordingly). Owner happened to be there when running one of the first loads and says "we need to be able to unload trucks faster than that". Wanted to say then you should have spent the money on something larger, which possibly was an option but he chose this one. I just told him that if you go more you are overloading that motor and it will shorten it's life.

I am having that exact same problem on grain leg at a facility our shop wired 18 years ago.

They burned the 15hp leg motor up a couple weeks ago, I came on site to check something else out and they mentioned the leg motor had burned up. I decided to open the MCC bucket for the leg to verify the OL's were set correctly, they were set to max scale, something like 85+ amps. I turned them down to 19 or so, don't remember exactly. The very next load semi load of grain came in a few minutes later and started tripping the leg overloads. It was running 21-28 amps. I simply told them either you have a mechanical issue or too small of a motor.

Now they are complaining trucks take to long to unload. Go figure.

 

[ptonsparky]

I am having that exact same problem on grain leg at a facility our shop wired 18 years ago.

They burned the 15hp leg motor up a couple weeks ago, I came on site to check something else out and they mentioned the leg motor had burned up. I decided to open the MCC bucket for the leg to verify the OL's were set correctly, they were set to max scale, something like 85+ amps. I turned them down to 19 or so, don't remember exactly. The very next load semi load of grain came in a few minutes later and started tripping the leg overloads. It was running 21-28 amps. I simply told them either you have a mechanical issue or too small of a motor.

Now they are complaining trucks take to long to unload. Go figure.

One my aggravation’s. They want 10,000 bu per hour out of a 3 to 5000 setup. Or new 10” bin unloads but still using a 6” truck auger. Or visa versa. The breaker is getting weak I hear. That dang red button keeps popping out.

 

[kwired]

I am having that exact same problem on grain leg at a facility our shop wired 18 years ago.

They burned the 15hp leg motor up a couple weeks ago, I came on site to check something else out and they mentioned the leg motor had burned up. I decided to open the MCC bucket for the leg to verify the OL's were set correctly, they were set to max scale, something like 85+ amps. I turned them down to 19 or so, don't remember exactly. The very next load semi load of grain came in a few minutes later and started tripping the leg overloads. It was running 21-28 amps. I simply told them either you have a mechanical issue or too small of a motor.

Now they are complaining trucks take to long to unload. Go figure.

The one I mentioned earlier was brand new, kind of a small leg only 20 HP motor maybe only 80' tall. I don't know how many bushels per hour it would have been rated for, but probably sounded fine when it was purchased, and most likely looked fine compared to whatever next size would have been price wise. Even if they would have run it hard until motor quit, you can about bet they would consider replacing with a larger motor - but thing they don't consider is the gearbox, belt and other components were not rated for the increased load either.