: : > : > :> I do thanks, unlike you, your description of a CDU, : > :> which is laughable. : > : : > : Lets hear yours, if you think you can do better. : > : : > : Here's a good walk-through : >> : where you will see that any sensible CDU design : > : includes the current limit on the recharge side. This : > : > Does it, looks to me that it limits current draw on the recharge : > side *when the CDU is discharging*, thus protecting the : > recharging side from possible overload. : : Doesn't that amount to the same thing!!!!!!
No, and you seem to have a sticky key on your keyboard.
: This type of CDU is only of any use at all if there is
: voltage drop in the wiring to the point motor when it operates,
: power supply is not up to supplying the full current required
: motor. Otherwise after initial switch on the capacitor does
Thus it would be bloody useless on a layout were one might be
operating multiple numbers of solenoids, sometimes simultaneously
(via a route setting matrix for example) and at other times
sequentially - the latter being the more usual.
: > : limits the *power* but allows the capacitor to charge
: > : to almost the full voltage (hence the same *energy*
: > : stored).
: > A CDU has to recharge in seconds, that is because the next
: > operation could (and probably will) be in seconds, the larger
: > CDU is (thus the more work it can do, either bigger or a
: > number of solenoids) the MORE current it will draw during
: > recharging phase -from the power bus in this case- and as the
: > OP's problem appears to be a lack of available amps...
: No, the amount of current drawn will be dependant entirely on
: resistance of the motor. As long as there is sufficient energy
: capacitor to throw the point a larger capacitor will be no
: than being able to throw another motor without re-charging.
Exactly, so unless the capasitor is overly large the unit must
charge quickly, or the next operation might not happen, these
units are not about limitting current draw during charging but
current avalible during discharge.
: > All a CDU is designed to do, to use a figure of speech, is to
: > give a "good kick up the arse" to the solenoid - it is not
: > designed to limit power draw during recharging because that
: > not the point of the unit, or shouldn't be...
: Yes, it must otherwise you will overload the psu.
Which, unless one designs the unit not to (as mentioned below, in
which case the solenoid will fail to operate and the unit will be
prevented from recharging) that is exactly what will happen if
the power supply or the unit is not of sufficient capacity, A CDU
is no substitute for an inadequate PSU!
: > :> Next you'll be suggesting perpetual motion...
: > :
: > : Why would I need to do that?
: > Because that is what you are suggesting, clue there is no
: > thing as a free lunch, if you double the voltage, you need to
: > double the current as there is little point in having mega
: > but no amps , think about it... One of the reasons why the
: > national grid distributes at a HIGH volts/watts and then
: > down to *lower* volts/watts (ultimately to 240v, typically,
: > UK domestic use), have it your way -with your magical
: > doubler"- and the national grid would distribute the street
: > supply @ ~ 110v and then up-convert to 240v at the intake of
: > end user.
: You miss the point doubling the voltage will double the current
: the motor (Ohm's Law), that will kick it harder. Because of the
: pulse the motor is not overheated by the higher voltage.
No, I get the whys and wherefores thanks, what I'm saying is that
in doing so (stepping-up) you need to increase the input current
used, always far more efficient (power use wise) to step-down.
It would actually make more sense for these point solenoids to be
made to work at a (continuous rating) of ~ 6 to 8 volts and then
power them for short periods at 12 to 16 volts, without any need
for a CDU.
10 years ago