[GreenKeys] Constant Current Spice Magnets

[Bob Camp]

Hi

Based on the model I can now take a stab at constant current loops. The 
question has always been just how much voltage you need to get the same 
effect as with a resistive loop.

If the "magic" point is the 40 ma current point then you need about 60 
volts on the loop to get to there in 830 us.

One error on the last message - the data on release was for a 10 ma 
rather than 20 ma release point. The 20 ma release point happens in 
about 320 us. That makes the "distortion" even larger assuming it is 
the only source of distortion.

One other observation. The coils are well coupled to each other even 
with the armature in the open position. If you wire the magnets in 
"anti-parallel" (this was on purpose .... repeat ... this was not a 
mistake ... it's a deliberate experiment ...)  you get an inductance of 
about 0.1 H rather than 2H.

Bottom line on the tube based constant current driver: it adds a little 
distortion. Not enough to worry about but it does add a measurable 
amount of distortion.

Bottom line on the Teletype solid state driver: It adds even more 
distortion. It probably adds enough to notice. It's quiet but you don't 
get a free lunch.

	Enjoy!

		Bob Camp
		KB8TQ