Author Topic: Loco current draw question  (Read 114 times)

ON28

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Loco current draw question
« on: September 13, 2020, 11:33:11 AM »
Hello all--

I've been wiring my HO NCE-powered layout and came across an interesting issue. My Intermountain F3 RP-Keep Alive-equipped loco showed a substantial voltage drop on a short (full wheelbase) segment of unwired track, slowed, then picked up speed when the KA kicked in. Conversely, my Atlas dual-mode GP38 -- without KA -- showed little hesitancy when crossing from powered to unpowered track. Is there a difference between these locos' minimum voltages? Should there be any slowing with a KA-equipped loco?  Thanks for your input.

KPack

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Re: Loco current draw question
« Reply #1 on: September 13, 2020, 07:08:34 PM »
Yes, KA-equipped locomotives slow dramatically when they hit a section of unpowered track.  A typical KA drops voltage very quickly and you will see that in the speed of the locomotive since it is by far the largest current draw between motor, sound, and lights. 

Ring did a really nice job with their KA (the PBM-2) because it's not just capacitors like everyone else.  They added some electronics to keep the voltage mostly stable when power is totally lost.  You will still notice a slight drop in speed, but not anything like a normal KA.  All my KA's now will be Ring's PBM-2.

-Kevin

ON28

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Re: Loco current draw question
« Reply #2 on: September 13, 2020, 09:14:58 PM »
Thanks for that.