alfuller194(at)gmail.com wrote:
> In the original post, the device in question was described as a 'continuous'
solenoid.
>
> Is that relevant, or am I just being pedantic?
The primary difference between continuous and intermittent duty solenoids is in
their coils. Continuous duty generally have higher resistance coils designed
to draw less current and therefore heat up less. They're designed to be on all
the time without overheating. Intermittent duty solenoids have lower resistance
coils that draw larger current. This makes them close "harder" at the expense
of greater heat, so they can't stay on continuously.
There is often a difference in their contacts as well. Intermittent duty solenoids
are often rated for much higher surge current than continuous duty. Their
aggressive closing velocity and pressure helps them carry higher loads.
The ones we use as battery contactors are continuous duty, while our starter contactors
are intermittent duty. Whether or not to run starter currents through
an already-closed battery contactor is open to debate, but I'm not doing it.
There are ways to protect the starter circuit against unwanted activation without
doing so (one example: a small automotive relay interrupting the starter
switch circuit, with its coil in parallel with the battery contactor's coil,
so that it pulls in at the same time as the battery contactor).
Does the OP's aircraft route starter current through the battery solenoid? If
so, could that have burned its contacts, causing a high resistance connection?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=516720#516720
