When would the Auto reset on motor starter be used?

[ptonsparky]

Power blips should very seldom cause problems with overloads especially if a PLC is invloved. Try a phase loss monitor. We have been starting stopping pivots, wells etc, for years with mechanical relays and phase monitors that don't come close to what is available today. Overloads should be tripping for reasons other than power condition if you have done you homework. Even with a sump I would think you would want to know the frequency of those ovld auto resets.

Then again 4hr service calls in the middle of the night should just pay pretty good.

 

[One-eyed Jack]

Why in the world did he go up on the conveyor without locking the thing out in the first place? LOTO is not just about something that might start up on its own. Its also about the guy who walks by from a downstream department to see why there is no product coming to him and sees the conveyor is stopped and restarts it not realizing his buddy was on the conveyor.

Its a little different with a PLC controlled system because presumably you have some fault detection and decision logic built in, and can alert someone what actually happened. Hopefully the logic realized it tripped and reset, and thats OK for now but it needs to be flagged so someone can go check on why it tripped.

I would not ever trust my life to pushing the stop button and hoping that the thing stays stopped while I climb on it, nor am I going to be climbing on something that mysteriously stopped for no obvious reason. Its not nice to say so, but the guy that gets himself hurt because he did not follow the proper LOTO procedure is the problem (or maybe the company is for letting him be so stupid), not a control system that restarted itself after a legitimate fault recovery procedure.

I didn't say he was the brightest bulb in the box Yes if he had LOTO it would not have happened. Personaly I don't trust anything not to go unless I have the fuse or the keys to the lock in my pocket. If it turns round and round and you get into it YOU get hurt. Same place OWNER was sweeping sawdust off a flat belt with his hand. It was running at the time and it grabbed his hand and ran it around the end roller. Damn near pulled his arm out of socket. He looked like he went a coupla rounds with a heavyweight boxer. Oh yeah,broke his arm in a place or two.

 

[John120/240]

Don't they usually have a horn or buzzer sound 20 seconds before restart?

 

[K2500]

Don't they usually have a horn or buzzer sound 20 seconds before restart?

Some equiptment does, but I've only seen it done on very large/long, or exceptionly dangerous equiptment.

 

[petersonra]

Don't they usually have a horn or buzzer sound 20 seconds before restart?

Its a good idea, but it makes no sense on equipment that starts and stops a lot. A lot of places have gone to shutting down conveyors that would otherwise run empty as an energy saving device. Its also a lot quieter.

Its not unusual for a conveyor to only be in use for short periods of time. Why run it all day when it only needs to run for a fraction of that time?

 

[hockeyoligist2]

Yes it would as you're talking about an unmanned facility and who would want to deal with the mess when the ca-ca hits the fan?

However, as the service tech, (I am presuming) it would be unwise for you to take on the decision to change those starters to auto-reset. Only the designer/engineer should make that decision.

Besides, if you get paid extra to respond to those calls, why cut yourself out of a nice cash cow? :grin:

"designer/engineer" is out of the picture.

It is up to me and the plant supervisor.

"Besides, if you get paid extra to respond to those calls, why cut yourself out of a nice cash cow?"

I get paid 4 hours for the first call if it takes me 10 minutes. If I have to go out 10 times in 4 hours, I don't get any extra!

LOL,

I'm getting too old to go out in bad weather in the middle of the night!

 

[hockeyoligist2]

Power blips should very seldom cause problems with overloads especially if a PLC is invloved. Try a phase loss monitor. We have been starting stopping pivots, wells etc, for years with mechanical relays and phase monitors that don't come close to what is available today. Overloads should be tripping for reasons other than power condition if you have done you homework. Even with a sump I would think you would want to know the frequency of those ovld auto resets.

Then again 4hr service calls in the middle of the night should just pay pretty good.

Yes, it pay's good on the first call, then it goes down hill!

Power blips very often cause problems with overloads when it is blink after blink. Not enough time for the PLC or phase protection to know that the power is off, but enough time to cause the starter to drop out and back in several times in a row. Most all of the motors are sized to the bare minimum ( Government bidding goes with the lowest bidder you know!) and pulling the max or close to max FLA.

Then you also have problems because of other machines feeding these pumps. If they drop out for a few seconds/minutes, the DooDoo gets thicker and makes it harder to pump!

Most people are not familiar with the problems at sewer plants. They are almost always at the end of the line when it comes to the power grid. Not many businesses or people locate on the flood plain of a river or creek! The POCO doesn't get around to trimming trees and doing maintenance over the hill and through the woods, if you get my drift?

 

[mxslick]

So now it comes down to a simple question:

Is it worth the money to allow motors to keep resetting automatically and run to failure or is it more cost-effective to deal with the manual resets?:grin:

I would imagine we're not talking about small motors either.

As for the four hours/ten minutes thing, in your position if I had to go out on a call to reset due to power blips, I would simply wait on site for an hour or two rather than turn and leave right away.

 

[big john]

This is a timely thread: Had a little 2HP 480V sluice-gate motor that had been dumping on O/L because of bearing-lube problems.

The mechanics "trouble-shooting" the problem got sick of re-setting the OL. So instead of "bugging me" they just put the OL reset in Auto. I can't say how many times over the next 24 hours that motor reset, but it was one-too-many:

Replaced the motor this morning.

-John

 

[hockeyoligist2]

So now it comes down to a simple question:

Is it worth the money to allow motors to keep resetting automatically and run to failure or is it more cost-effective to deal with the manual resets?:grin:

I would imagine we're not talking about small motors either.

As for the four hours/ten minutes thing, in your position if I had to go out on a call to reset due to power blips, I would simply wait on site for an hour or two rather than turn and leave right away.

The one that gives the most problems is a 10hp motor. The plant supervisor doesn't want to install a bigger motor until this one lets the smoke out. I have a 15hp, the manufacturers recommended size, sitting on the shelf waiting for it to happen. Which will probably be 2AM with no help to change it out!

The sitting on site thing doesn't work out very well. I wait around at least a half hour to make sure everything is OK. It is usually after midnight and I have to get up at 5AM to go back to work. The boss doesn't care if you have been up all night, he expects you to be there bright and early!

PS The plant supervisor decided to put it in auto reset mode after my first post.

 

[Besoeker]

Power blips very often cause problems with overloads when it is blink after blink. Not enough time for the PLC or phase protection to know that the power is off, but enough time to cause the starter to drop out and back in several times in a row.

If it's long enough to cause the starter to drop out, it's long enough to drop out a timer that would prevent an instant restart.

 

[TxEngr]

Your last post raised a few questions.

Does the motor only trip out on O/L at night or is it also doing this during the day when you are there to reset it? If it's only tripping off at night, you might want to do a little investigating to see why that is. There may be a problem with some other part of the process tripping things off.

The next time you get called out in the middle of the night, just replace the motor. No one will know the difference of whether it failed or just tripped out and you will have solved your problem. Stage your new contactor and overloads (and fuses or breaker) for the larger motor before you go home and just plan the job for an odd time. Then make sure the motor is fully failed when it goes to the motor shop. Or if you're like us, it just gets tossed anyway. Problem solved.

We can now begin the ethics discussion......

 

[mcclary's electrical]

Your last post raised a few questions.

Does the motor only trip out on O/L at night or is it also doing this during the day when you are there to reset it? If it's only tripping off at night, you might want to do a little investigating to see why that is. There may be a problem with some other part of the process tripping things off.

The next time you get called out in the middle of the night, just replace the motor. No one will know the difference of whether it failed or just tripped out and you will have solved your problem. Stage your new contactor and overloads (and fuses or breaker) for the larger motor before you go home and just plan the job for an odd time. Then make sure the motor is fully failed when it goes to the motor shop. Or if you're like us, it just gets tossed anyway. Problem solved.

We can now begin the ethics discussion......

you're a crook:grin:

 

[hockeyoligist2]

Your last post raised a few questions.

Does the motor only trip out on O/L at night or is it also doing this during the day when you are there to reset it? If it's only tripping off at night, you might want to do a little investigating to see why that is. There may be a problem with some other part of the process tripping things off.

It normally only trips during storms, It is manned during the day and the plant operator resets it if it trips. And yes it is mostly due to the process. Some things go off with a power blip and then they are restarted by the PLC after a delay of a few minutes. It is a sludge pump that runs for 5 minutes every 30 minutes and doesn't have a restart delay. I had one in the PLC program when I first wrote it and it caused other problems within the plant so I had to take it out. The other machinery being off for a few minutes causes the sludge to get thicker and the already maxed out motor can't handle it, especially if the power blinks while it is running.

 

[kwired]

Your last post raised a few questions.

Does the motor only trip out on O/L at night or is it also doing this during the day when you are there to reset it? If it's only tripping off at night, you might want to do a little investigating to see why that is. There may be a problem with some other part of the process tripping things off.

The next time you get called out in the middle of the night, just replace the motor. No one will know the difference of whether it failed or just tripped out and you will have solved your problem. Stage your new contactor and overloads (and fuses or breaker) for the larger motor before you go home and just plan the job for an odd time. Then make sure the motor is fully failed when it goes to the motor shop. Or if you're like us, it just gets tossed anyway. Problem solved.

We can now begin the ethics discussion......

If the motor was not the problem you solved nothing.

It also would not look good at all on say a 50 hp motor. Someone would notice there was a fairly significant cost and that the thing still does the same thing it did before you "fixed" it.

 

[TxEngr]

My somewhat 'tongue-in-cheek' comment was based on the statement that they were going to upgrade the motor to 15 HP as soon as the 10HP motor failed. Since they were going to upgrade anyway, he could simply hurry the process. Also, the problem seems to be based on process which is an increase in the consistency of the product being moved after a power outage creating a larger horsepower requirement than the 10HP motor can handle. The manufacturer's recommended 15 HP motor would likely help with this problem. I'm also assuming that the 15 HP is the maximum HP for this piece of equipment.

Since they plan on upgrading to 15 HP once the 10HP fails, they probably have the spare 15HP motor staged and the purchase is already made, so it wouldn't be obvious to anyone.