[modeleng] Re: Electric Traction Problems

John,

As you are well aware, any system of regulating electricity that involves 
any type resistor (other than those wee little fellows in electronic 
circuits) gobbles up power just like the regulated device does, just turns 
it into heat instead of usable power..  I ain't an electronic wizard as I 
lose the electrons when they get into them diodes etc, but I have designed 
many control circuits for 12 volts up to 440 volts AC.  I suggest you find 
some electronic brain who can design you a circuit that does not employ 
heavy resistors, but instead, it regulates electronically and also has 
regenerative braking to help keep your batteries charged longer.

Surely someone out here in the model engineering world can come up with 
something that will be capable of handling the load.

Jesse the REDNECK over in the New World

I'm not sure how to make a carbon pile regulator, but I imagine there must 
be something on the net. It's old technology after all.

Just a couple of other thoughts..

1)rotary stud switch with home made BSRs (big sweaty resistors), perhaps 
from a scrap electric fire. I haven't done any sums on this, I suspect you'd 
need several in parallel to take the current.

2)I looked at some fork lift truck control circuits many years ago. In those 
days the only high current device available was a thyristor, which was fine 
for turning on but needed something a bit clever for switching off. From 
memory, one thyristor was turned on, and to turn it off, another thyristor 
in parallel shorted it out (the only way to turn them off was to remove the 
supply or let the current drop to zero). The cunning thing was that this 
second thyristor had a capacitor in series, which charged up to the supply 
voltage. At this point the current in the second thyristor fell to zero, so 
it too turned off. I seem to remember the capacitor was referred to as a 
commutating capacitor. One obvious question is how the second thyristor 
turns off the first - I guess something is arranged to ensure that the volts 
drop across the second is less than the first.

You've whetted my appetite so I'll have a rummage on the web and see what I 
can find.

JohnP

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