Burning contactors

[weldon]

I have an 36 volt electrical Hyster standup lift. The lift has two elctric motors, one for movement of the lift the other is movement of the mast. The contactors for the mast motor completely burn out in 7 - 10 days. I am unable to find a reason for this. There is minimal arcing on the break of the contactors, less than the contactors for the drive motor. Battery has been removed and load tested by manufacturer. Motor has been removed and bench tested by an outside company. All connections are clean and corrosion free. Amp draw under full load is within specifications. Hyster repairman ran up a bill of over $1000 replacing parts. Still having the same problem. Does anyone have any ideas?

 

[instrument1717]

My Opininon : If possible Try with Better Contactors of different make ( Fast switching with bettter rating specs ).

 

[oldfieldguy]

Make sure the contactor is connected with the correct polarity across the power contacts. Many high-current DC contactors depend on the correct polarity for magnetic arc suppression.

old field guy

 

[dV8r]

Duty cycle.
Most operators jog themselves into position, this generally exceeds the Start/Stop duty cycle. Builds up heat and current, the weakest link will suffer from this.
So instrument1717 may have a point.

 

[jraef]

I agree on the duty cycle. Your current may be within spec, but too rapid of cycling will overheat them nonetheless. Go with a higher rating at least. And I didn't know about the polarity issue, interesting.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
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[Mike2468]

Have you considered a solid state contactor?

 

[itsmoked]

Duty cycle; You may have a weird driver in the graveyard shift or something along those lines. As the contact temperature rises from cycling - the contact life severely drops.

The other thing is that the hydraulics could have a restriction so the motor always starts against head pressure or the head pressure builds in only a revolution or so. This is the one area you have not had tested and I have seen this kind of problem with regard to the hydraulics.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[waross]

It sounds like operator error. The other thing to check is the field circuit. If you have any high resistance points in the field circuit that are reducing the field current the armature current will be excessive.
respectfully

 

[dydt]

how about the infamous mercury contactor... i have an application that constantly burn contacts and blowing SSR's and after we installed a 3 pole mercury contactors, my electricians now have more time reading newspaper in the shop..

btw...i am talking about sets of 14 starters

 

[ScottyUK]

The rather old-fashioned looking bar type contactors are a great choice for heavy DC switching. Most types employ a magnetic blowout in the pole assembly which makes for a very effective arc extinguishing action. The only downside might be physical size and perhaps cost, although for $1000 you should be able to oversize it at least one full frame size and solve the burning out problem the Victorian way: brute force. ABB's R-Line contactors are one species; similar types are also offered by Telemechanique, Hubbell, and Siemens. From personal experience the Telemecanique product is very tough - we had some employed on a DC timestarter which had a 'minor' wiring problem which resulted in a peak breaking current of 1400A through a contactor pole rated for 170A and the pole was almost pristine. I rarely have anything positive to say about Telemecanique products, so take that as high praise indeed!

http://www.abb.com/Product/seitp329...8e0040fe25.aspx?productLanguage=us&country=US

http://www.telemecanique.com/en/search/index.htm

and enter [blue]cv1 cv3 bar[/blue] in the search bar for a load of hits. Doesn't work too well in Firefox - use IE6 instead.

The Siemens online catalog is so awful that I'm not wading through that mess looking for their contactors - the paper CA 01 catalogue is a better bet if you can get a copy.

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