Setting thermal overloads three phase direct on line motor

[Buzz1980]

Hi all can anyone give me there thoughts on setting of thermal overloads. I have heard all types such as set them at 110% of FLA. Set them 125% of FLA. Set them at 100% of FLA. Get running current and set them 10% above this. But I have heard a lot set them at 110% to avoid nuse tripping?

Thanks trig

 

[Engineer54]

Set standard motor controler thermal overloads at 100% FLA, not at 110 or 125%!! Just think about what you are doing by setting the thermal protection of a motor.....

 

[Buzz1980]

Set standard motor controler thermal overloads at 100% FLA, not at 110 or 125%!! Just think about what you are doing by setting the thermal protection of a motor.....

Hi there thanks for replying. I was just wondering why so many people I speak to set them at 110%. Why are they setting them higher than 100% ?

thanks

 

[Engineer54]

Hi there thanks for replying. I was just wondering why so many people I speak to set them at 110%. Why are they setting them higher than 100% ?

thanks

Because most of those have little to no working knowledge of motor protection. I've even heard of college lecturers coming out with this sort of crap, which to me just goes to show the standard of some of these college lecturers today. let alone some of the scaremongering views many persist in perpetuating!!

Those 110/125% etc of FLC, stem from the era of the old oil filled dash pot overloads, they have long since disappeared, no compensation is now necessary on the modern motor overload modules of today....

 

[Darkwood]

As expressed already by E54....set to FLC of motor, if you are experienced in this area then lower than FLC may be set up by knowing the running current demand of the motor - this can be used as an early warning indicator of issues like worn bearings etc etc which can be rectified immediately by changing O/L to FLC and programming a shutdown service in when more convenient.

 

[Knobhead]

Those 110/125% etc of FLC, stem from the era of the old oil filled dash pot overloads, they have long since disappeared, no compensation is now necessary on the modern motor overload modules of today....

They’re still out there. Most will have a plate stating the setting level. For cane duty they also provide S/C protection. Cranes are a special case where the motors are dual rated for short term and continuous running.

Thermal O/L’s set at 100%

 

[Engineer54]

They’re still out there. Most will have a plate stating the setting level. For cane duty they also provide S/C protection. Cranes are a special case where the motors are dual rated for short term and continuous running.

Thermal O/L’s set at 100%

Let's hope these old dash pot contactors are being maintained then. But i'm sure you're right in that there still lurking around and still filling a function, although i haven't personally seen any of them around for now for literary donkeys years....

 

[Knobhead]

I doubt you will in your line of work.

Not all of us work with nice shiny new gear.

 

[joel89]

They’re still out there. Most will have a plate stating the setting level. For cane duty they also provide S/C protection. Cranes are a special case where the motors are dual rated for short term and continuous running.

Thermal O/L’s set at 100%

I've only ever seen them on fuses tony, never knew they used Thermals OL'S

 

[Knobhead]

Non of the cranes I’ve worked on had fuses or thermal O/L’s.

 

[Geordie Spark]

Non of the cranes I’ve worked on had fuses or thermal O/L’s.

Surely they would have had Fusible Plugs in their boilers in case the water got a bit low??? :angel_smile:

 

[Knobhead]

No joking Geordie, I have worked on a steam crane. It’s now at Rutland railway museum along with two of our loco’s.
I’ve got some pictures of it, I’ll send them to you later.