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ECP braking -Better Call Saul

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Posted by CSX Robert on Thursday, March 9, 2023 4:37 PM

adkrr64

What voltages are involved in the locomotive MU cables? Those get plugged/ unplugged all the time without any special precautions to power them down.

 

According to this, 74 volts DC.  Something else to consider, I believe the MU cabling is all signal and control, and not providing significant power to anything so wouldn't provide much current, whereas the ECP brake cable would have to provide enough current to power 200+ brake controls.

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Posted by tree68 on Thursday, March 9, 2023 4:50 PM

adkrr64

What voltages are involved in the locomotive MU cables? Those get plugged/ unplugged all the time without any special precautions to power them down.

I just asked someone who would know, but he's not here on the forum.  I'd guess nothing over 72VDC.

Edit:  MU cables carry 74 VDC control voltages, at least in the old stuff we run.  I'd have to believe we could still MU our old ALCOs with anything modern.

LarryWhistling
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Posted by oltmannd on Monday, March 13, 2023 7:49 PM

tree68

 

 
adkrr64

What voltages are involved in the locomotive MU cables? Those get plugged/ unplugged all the time without any special precautions to power them down.

 

I just asked someone who would know, but he's not here on the forum.  I'd guess nothing over 72VDC.

Edit:  MU cables carry 74 VDC control voltages, at least in the old stuff we run.  I'd have to believe we could still MU our old ALCOs with anything modern.

 

74VDC.  And they don't carry for more than a dozen or so connections, reliably.  RRs have rules about how many locos can be MUed.  Also, you have to do a continuity check every time you build a consist.

MU connectors and cable do fail and get burned contacts, but they are pretty reliable - they also "fail safe".  

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by BaltACD on Monday, March 13, 2023 9:48 PM

oltmannd
 
tree68 
adkrr64

What voltages are involved in the locomotive MU cables? Those get plugged/ unplugged all the time without any special precautions to power them down. 

I just asked someone who would know, but he's not here on the forum.  I'd guess nothing over 72VDC.

Edit:  MU cables carry 74 VDC control voltages, at least in the old stuff we run.  I'd have to believe we could still MU our old ALCOs with anything modern. 

74VDC.  And they don't carry for more than a dozen or so connections, reliably.  RRs have rules about how many locos can be MUed.  Also, you have to do a continuity check every time you build a consist.

MU connectors and cable do fail and get burned contacts, but they are pretty reliable - they also "fail safe".  

All depends on what the definition of SAFE is.

https://www.ntsb.gov/investigations/AccidentReports/Reports/RAR0202.pdf

 

Because of MU failure engineer only had Dynamic Braking on the lead unit, not all three units like he thought.

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Posted by jeffhergert on Tuesday, March 14, 2023 9:54 PM

When an engine is acting up for no obvious reason, pull the MU cable and see if that helps.  Many engines now have a dummy receptacle for both ends of the MU cable.  Sometimes leaving one end plugged into the live receptacle, even with the other end in the dummy slot can cause strange things to happen.

Jeff

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