Overload protection - grizzly vibrator

[enxago]

Hello,

First of all, i want to tell you that english is not my mother tongue so sorry for my mispelling.
I want to know if you would tell me if a falk coupling with some teeth broken could cause an increase in the torque that outcome in an electric motor overload.
Do you understand me?

Thanx. Bye.

 

[msquared48]

Seems that missing teeth could produce an "impact" loading, if you will when the remaining teeth reingage, depending on the pattern of missing teeth and the length of the engagement.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[enxago]

Thanx for your answer.

But do you think that a semibroken-coupling can increase the current that gets into the electric motor? Can a coupling affect to the torque that an electric motor has to provide?

 

[desertfox]

hi enxago

No the broken teeth on the coupling wouldn't increase the motor torque.
The torque from the motor is governed by the load on the vibrator. If the load demand increased on the vibrator, then the motor would supply more torque and the coupling would fail if it was undersized or overloaded beyond its designed torque.Another possibility was the coupling was assemblied misaligned during installation.
If the machine as been running a while it could be fatigue.If you can post a picture of the failed coupling we might be able to help you further.

desertfox

 

[MintJulep]

Doubtful.

It seems much more probable that whatever overload exists on the Grizzly broke the coupling and tripped the motor protection.

 

[FMJalink]

Enxago,

Looking to the application of the gear coupling: being in between two vibrators. It could be that the missing teeth cause some misalignment, with as result a (substantial) increase in required torque.

I do not know whether you have problems during start-up, normal operation or high speed (assuming you that the vibrator is of the unbalance type)?

Assuming the problem to be with high speed: If the torque required by the vibrator assembly at a rotational speed is higher than the AC electric motor can supply, will the motor “try” to compensate this with more slip. This will increase the electric current through the motor.

 

[ornerynorsk]

Short answer is that if any of your broken coupling parts are causing binding, yes, it may greatly increase the load. We had this exact experience in a circulator drive in one of our powder ovens.

 

[bklauba]

Grizzly vibrators applications normally require some pretty rugged hardware. Asking a gearbox to adjust the motor speed to the required vibration speed needless complicates things: You would be better off using a vibrator with the correct speed initially, and if some adjustment is needed, go the VFD route.

Rotary electric vibrators are probably the most commonly overloaded electric motor apps in industry. Grizzly apps are even worse. There are plenty of good vibrators to chose from, but some good installation and testing procedures are needed to keep whatever you use within its range of "non-destructive-ness". Good overload protection is a must; we have had the best results by using solid state overloads, and in very rugged apps, an RTD embedded in the motor windings, with suitable module in concert with the O/L circuitry, to provide the most comprehensive protection. Much easier and cheaper to tighten bolts or weld repair cracked welds, than have to rip out (esp a large) vibrator and replace it.

It's amazing how much mechanical use, almost abuse, a motor can take if you limit overloading and the heat it generates.

BK