On Thu, 31 Mar 2005 14:57:41 -0500, Jeff Wisnia
wrote:


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.

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.