(OT) Need inductive load

The test method we are testing to (MIL-STD-202, method 109, available at

't the best I've seen. As for the inductance, it states "Proper precaution shall be taken to duplicate the normal load in respect to torque, voltage, current, inductive reactance, etc. In all instances it shall be considered preferable to operate the specimen as it normally functions during service use." However, when you look at MIL-SPEC switches that are already rated for use in explosive atmosphere, that are always tested at the maximum inductive current "in accordance with MIL-STD-202, method 109", so that is what we are trying to do.

And as far a litigation, we are covered by "The Government Contractor Defense". ;^)

#! rnews 1379 Xref: xyzzy rec.crafts.metalworking:615347 Newsgroups: rec.crafts.metalworking Path: xyzzy!nntp From: "Ken Finney" Subject: Re: (OT) Need inductive load X-Nntp-Posting-Host: e244847.nw.nos.boeing.com Message-ID: X-Mimeole: Produced By Microsoft MimeOLE V6.00.2800.1441 X-Priority: 3 X-Msmail-Priority: Normal Lines: 18 Sender: snipped-for-privacy@news.boeing.com (Boeing NNTP News Access) Organization: The Boeing Company X-Newsreader: Microsoft Outlook Express 6.00.2800.1437 References:

Date: Thu, 31 Mar 2005 17:28:30 GMT

Sorry I wasn't clearer, yes, we have to close and open the switch under test. And no, the inductance isn't specified (even though it should be).

isn't the best I've seen. As for the inductance, it states "Proper

Well, it does now sound like you've got a problem on your hands and if it were me I'd jump up and down screaming that the inductance should be specified or at the very least, the specific piece of equipment being controlled by that switch, such as a motor, a big solenoid actuator or whatever be defined as the expected (and only) load your swich will be rated to work with.

Is this perhaps an "explosion proof" switch? i.e. one mounted inside a strong metal housing so that even if a hazardous atmosphere inside the enclosure gets touched off by a spark from the switch it won't "leak out" enough hot gas to ignite a hazardous atmosphere outside of the enclosure. IIRC one operating principle of such housings is that the path length of the cover flanges on them is long enough so that any hot gasses from an explosion inside them which squirt through the joints get cooled by contact with the metal path so that they aren't hot enough to ignite the atmosphere outside the enclosure.

IMHO breaking 12 amps of dc with even a tiny amount of inductance in the circuit is quite liable to set off the atmosphere specified in the document you referenced, I'd run like hell if the switch isn't an "explosion proof" design.

Jeff

Heck no. If I were in his shoes, I'd use the standard value for that: 2 picoHenries!

Jim

At 12 amps and 28 volts, the inductance value doesn't matter. Even a purely resistive load will produce enough spark to ignite an explosive mixture. Adding inductance increases the duration, length and energy of the spark, but once ignition is accomplished, more ignition is irrelevant.

Yes, do it that way and he can probably save himself about $21 million and still get into orbit.

Jeff

That was not my point -- the question had been asked if the available inductor had too low a resistance was it legit to add series resistance. My answer stands -- you are correct that series resistance does not change the value of the inductance, HOWEVER, if you simply pick some coil and add series resistance to limit the current, you do NOT have anywhere near the inductance that you would have if you had enough wire in the coil to limit the current with it's own resistance. Look at the case I gave -- taking it to the extreme, 1 loop of wire with a series resistor is NOT the same as a large inductor with 2+ ohms worth of wire in it. Go back and READ YOUR BOOKS.

That was the question, and yes it is.

OK.