Eutectic Alloy Overload Relays

[adamscb]

I feel like I should know the answer to this question, but here we go: Normal eutectic alloy overload relays, if they trip on overload and you try to reset them immediately, will they trip very soon? Or do they 'reset' in a sense, and start off again as if you just started the motor?

If I were to guess I'd say the first choice, but not 100% sure.

 

[GoldDigger]

I feel like I should know the answer to this question, but here we go: Normal eutectic alloy overload relays, if they trip on overload and you try to reset them immediately, will they trip very soon? Or do they 'reset' in a sense, and start off again as if you just started the motor?

If I were to guess I'd say the first choice, but not 100% sure.

You are absolutely right. They will not be starting from scratch until they have had time to cool. Which is good because the same applies to the motor temperature.
A good electronic overload will use memory to behave the same way.

 

[ptonsparky]

Eutectic overloads can be ruined by resetting them to soon and or repeatedly. AB were notorious for the alloy separating. I picked on AB because those are the ones I am most familiar with.

 

[jim dungar]

Eutectic overloads can be ruined by resetting them to soon and or repeatedly...

Many thermal units that spin freely can be 'fixed' by heating them to their melting point, about 140F, and then letting them cool down.

 

[ptonsparky]

Many thermal units that spin freely can be 'fixed' by heating them to their melting point, about 140F, and then letting them cool down.

I've done that but was never satisfied over the long term and that could very well have been the operators failing to "wait". They are pressed for production and I tell them to have patience and slow things up.

 

[jim dungar]

I've done that but was never satisfied over the long term and that could very well have been the operators failing to "wait". They are pressed for production and I tell them to have patience and slow things up.

You almost can't really break a eutetic type of element.
The good thing about them 'failing to wait' is that the motor gets a chance to properly cool down while you are installing replacement elements.

 

[Jraef]

Eutectic overloads can be ruined by resetting them to soon and or repeatedly. AB were notorious for the alloy separating. I picked on AB because those are the ones I am most familiar with.

So a LONG time ago, the old "N" type OL heaters had the solder pot and pawl in the relay base and just the heater element was placed over it. So if people got annoyed with nuisance tripping, they'd keep increasing the size of the N heater element until they would literally cook away the solder by over heating it until the seal on the pot case melted (let's leave out the motor damage issue for this). In the early 80s, A-B changed to the "W" elements, in which the solder pot and pawl are on the replaceable element part, the relay base only holds the ratchet and contact mechanism. So when you replace or increase the size of the W heater, you are also replacing the solder and pot, therefore repeatedly trying to make it fail is less likely to succeed. The motor damage still happens of course...

Back to the OP's question, the reset time, which for a eutectic is the solder solidification time, is part of the eutectic alloy preparation, specifically to match the cool-down rate of a standard NEMA spec motor. You cannot* make it reset any faster than it is designed to.

*That's not meant as a challenge... I suppose with some cold spray or something exotic like that, you could.

 

[ptonsparky]

So a LONG time ago, the old "N" type OL heaters had the solder pot and pawl in the relay base and just the heater element was placed over it. So if people got annoyed with nuisance tripping, they'd keep increasing the size of the N heater element until they would literally cook away the solder by over heating it until the seal on the pot case melted (let's leave out the motor damage issue for this). In the early 80s, A-B changed to the "W" elements, in which the solder pot and pawl are on the replaceable element part, the relay base only holds the ratchet and contact mechanism....

I am still replacing those "N" type overloads but at a much lower rate and LONG time ago is a matter of perspective.

 

[kwired]

I've done that but was never satisfied over the long term and that could very well have been the operators failing to "wait". They are pressed for production and I tell them to have patience and slow things up.

Seen that before. Got a service call one time on a product auger that kept tripping motor overload, and they needed to get their run of product done because a truck was coming same day to pick up that product. Might have taken 30-45 minutes for me to get there. Starter was in a location remote from the motor and at that point they had dedicated one employee to sit in front of the motor starter and reset it as soon as it tripped.

I go out to the production area and the motor is hot enough to cook with. Of course I find a mechanical problem as the cause for overloading, but since it was an electrical component that was the item causing the shut down it must be an electrical problem right?

 

[Jraef]

... and LONG time ago is a matter of perspective.

When I started doing industrial work in 1978, the 509 starters (where they began using the W heaters) were not yet released. When they did, it was a total PITA for us, because we had thousands of 709 starters installed with N heaters. So we had to build a new huge rack to start holding the Ns + the Ws for a few years. When I left the steel mill, so few of the 709s remained that they merged the racks into one, and I took the old rack for the Ns home and made it into a spice rack. Still have it to this day.

Yeah, it is a matter of perspective...