mikeeasley(at)aol.com
Guest
|
 Posted: Thu Oct 15, 2009 6:14 am Post subject: Bi-Directional Zener vs. Diode and Zener in Series for Coil |
 |
|
In the SnapJack literature, Eric shows the comparative merits of various forms of coil suppression. One option is the diode and zener in series. Eric list this option as "second best", showing the downside of having to get the polarity right. I think I can overcome that!
I ran this question by the engineer at Kilovac Tyco, specifiying the Tyco LEV100 contactor in a 24-28V electrical system and his response was:
Use a 1N5406 or equivalent for the blocking diode, and a 1.5KE39A voltage suppressor diode or equivalent for the clamping diode. Connect them common anode, and connect the cathode of the blocking diode to the +24 Vdc line of the coil, the cathode of the TVS diode to the coil return. Common clamping for a 28Vdc aircraft system is -42V maximum, and most contactors rated to MIL-Specs have coil suppression using a diode+zener diode combo. Bi-directional zeners are not generally used due to concerns of higher overvoltages expected during lightning strikes. The failure mode, you have to assume is the worst thing, which is a short, but as I mentioned, this suppression method is pretty robust, and common for this type of application. This will also give the best performance for the contacts.
So is anyone willing to explain why the diode-zener diode is more robust than the bi-directional zener (SnapJack) method?
I understand that you have the ability to control the ratings of each diode which might be preferable to a bi-directional diode where you don't.
Mike Easley
Colorado Springs
[quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
