Contactor Not Getting Dropoff for Long Distance Cable Due to Cable Capitance.

Check out this link : moeller

Dear Sridhar,

I had already gone thru Moeller litrature & based on same I had calculate Coupling Cap.

Ah, sorry, i didn't know. Anyway, my preference would be to use DC coils... easier now since most good companies are offering electronically controlled contactors, fom50A(AC3) onwards ...

Dear Sridhar,

Thanks for your suggestion, but as you know using AC as control supply is totally customer/consultant choice. As a design engineer we can suggest but final descion is of customer/consultant . I normally suggest adding capacitor & it works fine. Am looking for any new idea /sugesstion for above problem.

Thanks

In our mining applications (emergency and normal stops on long conveyors), we used DC. Most of the control was AC, and the details on what we did are a little hazy, but we converted the minimum amount of the circuit to DC by installing a full wave rectifier to send DC through the stop circuit, and, typically, used an auxillary control relay at the motor starter to accept the DC and open the circuit to the motor starter coil.

(Actually, these were always field changes to a variety of manufacturer's equipment, so we looked for the easiest ways to accomplish this based on the design of the control circuit.)

This was all 30+ years ago. If anyone had been resistant to using DC instead of AC for the control circuit, I would have told them that the control circuit was AC, but we had to make special provisions (a "long distance stop circuit" ;-) for long conveyors and such.

Thanks all friends, Am aware that using DC in this type of application is fine, but am looking more solution in AC only.

Just looking back at what I wrote, maybe the last paragraph is a little ambiguous--today I would change the "was" to "is" and make it read as follows:

"This was all 30+ years ago. If anyone had been resistant to using DC instead of AC for the control circuit, I would have told them that the control circuit is AC, but we had to make special provisions (a "long distance stop circuit" ;-) for long conveyors and such."

Also, just to be clear, that added relay was (is ;-) wired into the circuit so that loss of signal stops the conveyor (and all are control was 3-wire control).

I found two possible pieces of info

1. http://www.eng-tips.com/viewthread.cfm?qid=217821

2. From another site

Can you inform me your mail ID thro this forum's mailbox so that I can send you some interesting articles on the subject? The articles are too large to copy & paste directly.

Can you provide links or citations to those articles, as I (and maybe others) are interested as well.

Are you using a solid state relay?

Solid state relays (optically coupled) will sometimes pick up enough AC voltage to stay closed. This can be prevented by placing a resistor in parallel with the input to the relay.

I would be uneasy with using a solid state relay in this application.

We use SEL which is having inbuild debouncing time feature. Please note Most of scheme We use contactor for interposing. It accept command from LCS. I know the problem ,I have working solutions. Am looking for new solutions in AC systems along with contactor to eliminate cable capitance voltage.

Thanks for your valuable feedbacks.

Regards