C-Pap power usage
So, I have been using my 12v(6.6 amps) C-Pap machine for a few years in my Creek Side. Now..........my wife is using a C-Pap. So far I have had my wife use my home unit(same exact one as in the trai...
Forum Discussion
pnichols wrote:MEXICOWANDERER wrote:
Again stick your finger onto the starter motor power terminal crank the engine release the key then scrape yourself off the wall.
It first - takes voltage (higher than 12 volts), then second - adequate current driven by that voltage for a person to get plastered to the wall.
I understand that the necessary current is available, but where is high voltage coming from during the engine starting procedure? The alternator of course is a source of relatively high AC voltage when it's spinning, but it's hardly doing that during engine start.
Induction in the starter motor or solenoid coils when the circuit is broken. Recall that an inductor is the complement of a capacitor; it tends to prevent changes to current (rather than voltage) by supplying or sinking voltage (rather than current). Open the circuit, and the current immediately goes from many amps to zero, and the response of the inductance of the coils causes the voltage there to spike. For this reason, coils on relays etc. often have snubber diodes or resistors to provide a path for these transients to discharge.
That particular voltage spike oughtn't make it back into the 12V system since it's on the disconnected side of the circuit, but there are other sources of probably lesser voltage fluctuations when the vehicle is started. Car and truck electrical systems are not particularly clean or stable supplies.
