Motor starter sticks temporaily in the on position - ideas?

[Brian Ruhlman]

I have a very heavy looking starter running a 5 HP single phase motor. I must hold the off button for an extented period of time before the contacts release. The contacts seem to sort of weld together - very lightly. One screw removes one contact. I pull all four contacts out, sand them smooth then use them again. After several starts it takes a longer period for the starter to open. I had used the machine for several years before this began. I am wondering if there is a coating installed orginally that prevents this arc induced pitting on the contact faces? It is time again to clean up the contacts.

All help is appreciated.

[Leo Zick]

resistance in the motor could be building up causing too much electron flow to the contacts. have you measured the resistance across them with an ohm/multi-meter? not sure of cause, but brushes could be on their way out. best to replace imo..

[jim sauterer]

if contacts are pitted badly they need to be replaced you shouldnt file them.you could end up burning out the motor.just my 2 cents

[Ken Fitzgerald]

First I'd check the brushes in the motor.

To pit the contacts, something is drawing too much current. That can be caused by either the motor drawing too much current. ...check the brushes or too much voltage applied to the motor causing it to draw more current.

[Bill Neely]

Most motor contacts have a silver alloy coating to prevent oxidation of the copper. When you start filing or sanding the contacts you aren't likely to be able to get the same profile that the contacts originally had and they will arc more as they make and break.

Could be mechanical too. If you haven't done so already, turn the power off and try operating the contactor by hand.

Cheers

[Rod Sheridan]

Brian, as I assume that this an induction motor, it doesn't have any brushes.

The most likely cause of the contactor sticking closed is dirt in the core of the contactor making it stick in the closed position. Remove the moveable core piece and carefully brush or blow the dirt out. Do not sand the core pieces.

The next most likely cause is a weak return spring.

It's rare for a contactor to be able to open welded contacts with just spring pressure. Often the contacts are welded together so well that you cannot salvage them.

If all else seems OK, replace the contact kit in case it is actually welding.

Regards, Rod.

[Brian Ruhlman]

Correct - no brushes. I will replace the contacts. I suppose the local electric supply shop.

Best Regards.

[Josiah Bartlett]

If you do need to file a set of electrical contacts, always use a points file, not sand paper. This was a common problem in the days of mechanical voltage regulators. You probably will have to replace them. The garnet in the sand paper leaves gouges, sticks in the gouges, and causes the contact area to get smaller, leading to local microwelds that make the contacts stick.

[Ron McAllister]

These guys have it pegged. You can sand the contacts for a temp solution, but in the long run, the start switch needs to be replaced. Once you compromise the factory coating, your on a session by session use after cleaning. Keep your motor as clean as possible and free of obstructions and routinely check your connections. If you have an amprobe (Amp meter) from time to time check your amperage. Make sure it dosen't exceed the FLA on the spec plate. Hope this helps.

[Brian Ruhlman]

I have looked for Lifeline Starter size 1-1/2 contact sets to no avail. Size 1 and size 2 sets range from 200 to $330. I am thinking I should be able to get a starter rated 5HP / 1 phase / 220v for less than what I think a contact set would cost.

Questions:

Know of a source for these contacts? Perhaps price will be favorable.
Alternatively, where would one purchase a good used starter?Thanks in advance.

[Ed Kilburn]

Give this site a try, I've used them often very quick to ship and great customer service anytime I needed to speak with someone.

http://web6.automationdirect.com/adc/Shopping/Catalog/Motor_Controls

[Leo Zick]

they normally arent the cheapest but did you check grainger?

http://www.grainger.com/Grainger/wwg/productIndex.shtml?L2=Motor+Starter&operator=prodIndexRefinementSearch&originalValue=motor+starter+contacts&L1=Contacts%2C

ebay also has a ton of starters listed.

[Brian Ruhlman]

I have not found contact sets for less that $250. I am thinking I will look for a good used or rebuild starter.

[Chee Fang]

I have a similar problem with my 5 HP single phase motor. When I push the "ON" button, the motor will run. But, it wouldn't turn off when I push the "OFF" button. You guys suggest that the contacts are sticking. Where are the contacts? Are they in the magnetic starter box?

Thanks for any help.

Chee