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Setting up instantaneous breaker and thermal overload for drag motor..

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ctaylo360860

Senior Member
Location
colorado
Occupation
ME
Hi I’m hoping to get some advice on setting up the instantaneous breaker and thermal overload for a drag motor on a grain bin system... the drag motor needs to stay on so that while they’re running leg and filling up the south bin it doesn’t plug the drag and spout back to the distributor. The motor is fed with #6 copper thhn. Thanks in advance all help and advice is much appreciated! 35B46E9A-59D6-446D-970F-7A7C74360346.jpeg
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
The IT and OL instructions will have the information you need.
As understand the manufacturer wants the overload to be set at the motor nameplate. the overload should then trip at 125% of what the overload is set at... the instantaneous breaker needs to follow 430.52 (3) exception no. 1... motor is design A- so I should be able to go up to 1300% if I understand what I’m reading correctly...
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
Looks like the OL is already set correctly. IT needs to be dialed back a bit IMO.
I agree with you there. If I understand 230.55 (3) exception one I should be able to adjust up to 1300% of the breaker handle? I haven’t set it in this picture, but that’s what I was inquiring about. I just really don’t want to have the drag motor trip out and plug up an 80ft legg, and another 30ft of the distributor pipe...
 
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ctaylo360860

Senior Member
Location
colorado
Occupation
ME
I hope you have some other control or power monitoring built into the system.
the leg motor Is on a soft start And Has a maxi tronic monitoring system. I didn’t not install this equipment, but as I understand this device will slow the leg motor down or completely shut it off if it begins to become overloaded. There is a buzzer and amp Meter that the guys who are running the equipment should be monitoring...however the drag motor on the top that I’m trying to set the ol and it for doesn’t have any monitoring. Word of mouth is the leg and the drag are rated the same bushel per hour, but no proof of this as there are no prints...

A2F93D79-6786-451D-92A4-1E15986A0CF8.jpeg
 

cpickett

Senior Member
Location
Western Maryland
Occupation
Electrical Engineer
I agree with you there. If I understand 230.55 (3) exception one I should be able to adjust up to 1300% of the breaker handle? I haven’t set it in this picture, but that’s what I was inquiring about. I just really don’t want to have the drag motor trip out and plug up an 80ft legg, and another 30ft of the distributor pipe...
The exception is that your instantaneous trip setting can be no more than 1300% of the FLC of the motor. Your FLC is 45A so your inst. setting should be 585A or less. Ideally you start low and work your way up to the max allowed.

The instantaneous really comes into play on startup of the motor, and the overload is going to protect the condition of running too much product for too long. If your OL is set properly (it is) and you have an issue of it tripping then either you have a mechanical binding, too much product, or the motor is undersized for the load.

*caveat - above #s assume 480V supply voltage*
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
The exception is that your instantaneous trip setting can be no more than 1300% of the FLC of the motor. Your FLC is 45A so your inst. setting should be 585A or less. Ideally you start low and work your way up to the max allowed.

The instantaneous really comes into play on startup of the motor, and the overload is going to protect the condition of running too much product for too long. If your OL is set properly (it is) and you have an issue of it tripping then either you have a mechanical binding, too much product, or the motor is undersized for the load.

*caveat - above #s assume 480V supply voltage*
When I spoke to the rep at Schneider electric he said that the value should be turned up to the breaker sized inside of the bucket not the motor fla... I also thought that’s how I should set the it too, but I can’t even get it to hold at 528 amps with no product running through it.... if I go up to the next value 631 it will hold but I’m worried once product is going through it, it will trip and cause a big problem... schnider rep says I should be able to go up to 13x the 80a breaker...
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
When I spoke to the rep at Schneider electric he said that the value should be turned up to the breaker sized inside of the bucket not the motor fla... I also thought that’s how I should set the it too, but I can’t even get it to hold at 528 amps with no product running through it.... if I go up to the next value 631 it will hold but I’m worried once product is going through it, it will trip and cause a big problem... schnider rep says I should be able to go up to 13x the 80a breaker lol. Do you think the motor is just that undersized, or do you think there is a mechanical problem with the drag? It’s all brand new, so we haven’t got to run it with product... the existing bin is built exactly alike and runs, but I’m pretty sure the existing electrician turned the breaker all the way up and the over load clear to 70amps...
 

paulengr

Senior Member
When I spoke to the rep at Schneider electric he said that the value should be turned up to the breaker sized inside of the bucket not the motor fla... I also thought that’s how I should set the it too, but I can’t even get it to hold at 528 amps with no product running through it.... if I go up to the next value 631 it will hold but I’m worried once product is going through it, it will trip and cause a big problem... schnider rep says I should be able to go up to 13x the 80a breaker...

Schneider rep is totally wrong. The setting is based on NEC Code and is based on FLC of the motor. If you put in a different size breaker the answer does not change. The setting is based on the breaker so if the handle reads 100 A and you set it to 5x, the setting is 500 A. But what setting you are allowed to use initially is 11x the FLC of the motor or less. If it trips you are allowed to increase it, ONE notch at a time, until it is no more than 17x FLA. So if it is 50 A you can set it to 5x using my example, no more since 50x11 is 550. If it trips, move to 6x and try again. Continue to no more than 50x17 or 850 A which means 8x even if the breaker has higher settings.

The initial surge is caused by the initial magnetization of the motor frame. It has nothing to do with the load at all. You get the same surge whether it is loaded or even uncoupled.
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
Your problems will be at startup. Once the equipment is loaded and if running properly you should not see anywhere near 500 or 600 amps.

You are starting a new system that is already giving grief. Look for a mechanical problem. Literally a wrench in the works. Is it turning the correct direction? Is the gear reduction correct?
Yeah tomorrow I planed on putting an amp meter on it to see what it’s pulling after start up... Yeah the existing one they did, had no gear oil in it, and only ran About 40,000bushel... It is turning the right way I believe as I heard wheat fall into the bottom of the bin. How would I check that? I’m not overly mechanically inclined, and there is absolutely no prints I have seen....
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
Schneider rep is totally wrong. The setting is based on NEC Code and is based on FLC of the motor. If you put in a different size breaker the answer does not change. The setting is based on the breaker so if the handle reads 100 A and you set it to 5x, the setting is 500 A. But what setting you are allowed to use initially is 11x the FLC of the motor or less. If it trips you are allowed to increase it, ONE notch at a time, until it is no more than 17x FLA. So if it is 50 A you can set it to 5x using my example, no more since 50x11 is 550. If it trips, move to 6x and try again. Continue to no more than 50x17 or 850 A which means 8x even if the breaker has higher settings.

The initial surge is caused by the initial magnetization of the motor frame. It has nothing to do with the load at all. You get the same surge whether it is loaded or even uncoupled.
I agree with you the Schneider rep is confused... wouldn’t I only be able to go up to the 1300% since this motor is design a and not b? Yeah so I set the it at 528, and it tripped Instantly. if I go to The next value on the breaker 631 it holds, but it’s over the 1300% by 46amps. The max I should be able to adjust the breaker should be 585, but I don’t know how I would tell where that setting is because it jumps from 528 up to 631.... the existing system runs, but they do not have the it breaker orthe overloads set up correctly. the breaker is as high as it can go on setting 1x from manufacture, and the overload is set at 75 amps with #6 wire.... tho I costing system has different type of it breaker. I believe it’s type h and the type in my mcc are type b...
 
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Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Yeah tomorrow I planed on putting an amp meter on it to see what it’s pulling after start up... Yeah the existing one they did, had no gear oil in it, and only ran About 40,000bushel... It is turning the right way I believe as I heard wheat fall into the bottom of the bin. How would I check that? I’m not overly mechanically inclined, and there is absolutely no prints I have seen....
Wheat falling in the bin is a good sign that it is turning correctly.

I do not believe I have ever seen a 3500 rpm motor on an auger. Sounds odd but we work with corn.
 

cpickett

Senior Member
Location
Western Maryland
Occupation
Electrical Engineer
OL should be set at 45A, the scale on the OL block already has 125% factored in.

Sounds like some more troubleshooting is in order. Uncouple the motor and try it. Is the motor wired for low voltage instead of high voltage? I was on a coal plant startup where we had a shaker screen that kept tripping the overloads, even after we cranked them up to max, above the motor limits. The millwrights doubled the motor size (new breaker, OL and wire to match) and it was still tripping. They loosened the belts and verified that the motor ran normally. Then they found the gearbox was full to the brim of oil and once they drained it to the proper level, ran perfectly.
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
Wheat falling in the bin is a good sign that it is turning correctly.

I do not believe I have ever seen a 3500 rpm motor on an auger. Sounds odd but we work with corn.
Yeah, I’m not sure what are rpms are on our augers Motors, but we run A few different products including corn... this name plate is for the drag motor so it’s more like a belt with a a chain on it...
 

ctaylo360860

Senior Member
Location
colorado
Occupation
ME
OL should be set at 45A, the scale on the OL block already has 125% factored in.

Sounds like some more troubleshooting is in order. Uncouple the motor and try it. Is the motor wired for low voltage instead of high voltage? I was on a coal plant startup where we had a shaker screen that kept tripping the overloads, even after we cranked them up to max, above the motor limits. The millwrights doubled the motor size (new breaker, OL and wire to match) and it was still tripping. They loosened the belts and verified that the motor ran normally. Then they found the gearbox was full to the brim of oil and once they drained it to the proper level, ran perfectly.
Yes I agree on the overload. that way your motor and conductors stay protected... by uncouple do you mean take the belts off and see if I can get the it breaker to hold at the lower value, or see if it trips instantly as well? I wired the motor I'm working on currently, so I'm pretty positive connections are correct. The old system seems to be wired correct as well. I just don't know why the old electrician set the values up so high in the mcc. I was hoping someone would have a some type of logical reason.... Yeah first thing the dam millwright did when he was filling the gear box was spill about 5 gallons on top, and down the side of the bin right where i was trying to work.... The guys I work with said that its full, but idk if the have checked to see if its too full.. looks like I will be doing more trouble shooting today... Corn harvest is here and I'm pressed for time, I would just really hate for the leg to get plugged because of me. I was wondering do you think exception in 430.52 wants you to use the full load current values given in 430.250 40hp motor shows its 52amps on 480 volts which would allow me to go up to 676amps? the dial I have it set on now is 631 and holding with no product running. as you said the In rush is what's tripping the breaker and they should have the drag motor up and running before they start running product through the drag, so if I can get it to hold at 631 because of inrush, it shouldn't be a problem once we start pulling product through as long as there are no mechanical issues causing the motor to overwork... or it being undersized...
 
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