RE: (ET) Traction motor current

[Larry Elie <lelie ford com>]

Hmm.... I need to do some digging.  You are right of course that it is the 
voltage dropped 
across the breaker that matters, but I'm not convinced that this is the 
same for a 36V, 50 A 
load as for a 220 V, 50 amp load.  For example, if the breaker voltage 
drop is 0.1%, on a 
220V, 50 Amp load is we have 4.4ohm total, .04ohm, the drop is .2 V.  The 
same breaker, 
4.4 ohm on a 36 V, 50 Amp load won't drop the same .2 V.  It drops 
significantly less V.  
I suspect proportionally less V.  That it is less than 1 V, or even .1 V  
in either case is not 
the important part; how different they are is the important part.  I 
missed that yesterday, and 
I don't want to neglect it today.  

Larry Elie


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From:   Paul and Sue Abendroth[SMTP:pabendro gemair com]
Sent:   Wednesday, October 27, 1999 4:20 PM
To:     Larry Elie; elec-trak cosmos5 phy tufts edu
Subject:        RE: (ET) Traction motor current

At 01:20 PM 10/27/99 , Larry Elie wrote:
>  I thought; so what, current is current, right?  Wrong.  The breaker in 
> an ET is a bimetallic strip.  It works by heating the strip to a given 
> temperature.  Current?  Well, the TEMPERATURE is related to the POWER 
> (current x voltage) and time.  Guess what?


Yes, but the voltage here is the drop across the breaker (less than a 
volt), not the voltage of the battery or the load. Therefore very little 
change in rating with voltage.

Paul and Sue Abendroth
pabendroth juno com
pabendro gemair com