Will this suppressor work?

PhilipD · Oct 29, 2011

Hi all,

I have a PLC that is used to energize a contactor to control a motor. Actually there are five of them. I want to put a suppressor on the coil to reduce back feed spikes to the output module. These are all 120vac coils. This suppressor was recommended but I'm not sure it will work. Will this one work or can you point me to one that will work. Thanks.

http://search.digikey.com/us/en/products/5KP170CA/5KP170CALFCT-ND/2095373

DamianInRochester · Oct 29, 2011

Hi Philip,
That's just a diode. That would be OK for flyback on a DC coil. You're better off with an RC style snubber.

Something like this
http://www.alliedelec.com/search/productdetail.aspx?SKU=3170077

DamianInRochester · Oct 29, 2011

Most coils we buy nowdays has the suppression built in, but when we do need to add one to an AC coil, these are the ones we use.

http://www.paktron.com/pdf/Quencharc_QRL.pdf

geoplc · Oct 29, 2011

Hi PhilipD,
The part in your link looks as if it is more for protecting a device from transient voltages not preventing them from being induced. That is basically what an MOV meatl oxide varistor does. I would use something similar to RedLions SNUB0000
http://www.alliedelec.com/search/productdetail.aspx?SKU=3170077

This is what I believe you are trying to accomplish, preventing your contactor coils from inducing noise in your system. You can also make your own with a capacitor and resistor in series but I cannot remember the exact values of the components. Hope this helps.

KalleOlsen · Oct 29, 2011

Hi PhD!
Here's an earlier post from "ddnnis" with a link to a relevant file.
http://www.plctalk.net/qanda/showpost.php?p=409668&postcount=6

Kalle

PhilipD · Oct 29, 2011

DamianInRochester said:
Hi Philip,
That's just a diode. That would be OK for flyback on a DC coil. You're better off with an RC style snubber.

Something like this
http://www.alliedelec.com/search/productdetail.aspx?SKU=3170077

Thanks Damian,

I don't have much experience with this type of stuff but I thought a diode was more for DC and that is why I wanted to check before I ordered any. The link you provided appears to be what I need. Again, Thanks!

PhilipD · Oct 29, 2011

geoplc said:
Hi PhilipD,
...Hope this helps.

Yes geoplc, it helps a great deal. Thank you.

PhilipD · Oct 29, 2011

KalleOlsen said:
Hi PhD!
Here's an earlier post from "ddnnis" with a link to a relevant file.
http://www.plctalk.net/qanda/showpost.php?p=409668&postcount=6

Kalle

Thanks for the link Kalle, it was most helpful.

JRW · Oct 29, 2011

What brand of contactors do you use?
Alot of time the manufacturer has a type that mounts nicely on their
contactors or starters

PhilipD · Oct 29, 2011

JRW said:
What brand of contactors do you use?
Alot of time the manufacturer has a type that mounts nicely on their
contactors or starters

2 are AB, 1 is Telemecanique, 1 is Square D and the last one is unknown. This last one was built in 1963 and I think most of the electrical is original.

RDS · Oct 29, 2011

That part is a TVS rated at 170V and is bipolar, which means it will work for AC. These type transient suppressors are very good for protecting semiconductor devices since they operate so fast. MOVs and RC snubbers are also good options. Your choice.

keithkyll · Oct 29, 2011

DamianInRochester said:
That's just a diode. http://www.alliedelec.com/search/productdetail.aspx?SKU=3170077

It's a TVS. Transient Voltage Suppressor. Bidirectional. Works like an MOV. It will work fine.
I like these.
http://www.factorymation.com/s.nl/it.A/id.61234/.f
RC snubber and MOV in a package with leads.

PhilipD · Oct 29, 2011

Thanks RDS, I'm happy to know it will work.

Keith, good link. That looks good to use also. Might just go with that one. But as long as the PLC is protected I guess any one of these will work.

Will this suppressor work?

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