[PRCo] Re: Interurban PCCs ???

[Boris Cefer]

Yes, the balancing speed (assumed on dead level) of an average PCC car with
full field excitation is roughly 30 mph. With the exciting field weakened by
the field shunts the speed at which all mechanical resistances equal the
tractive effort is higher, roughly 42 mph. That's correct for roughly 50 %
field shunting. With higher field shunting (67 % on those 16s and 17s with
WH equipment) the balancing speed on dead level would be higher, but I can
only speculate how much. When the high field shunting is applied, the rate
of acceleration at higher speeds (with the accelerator resistance
shortcircuited) is slightly higher, which was possibly the main intent of
that improvement. Possibly the high shunting allowed the cars to gain speeds
in slight excess of 50 mph and therefore the overspeed relays were included
in the schematics to avoid motor damage (maximum safe motor speed is just 50
mph).

Am I missing anything by the EMF? Ah, the language! :-)

Boris

----- Original Message -----
From: "John Swindler" <j_swindler at hotmail.com>
To: <pittsburgh-railways at dementia.org>
Sent: Sunday, March 27, 2005 7:46 PM
Subject: [PRCo] Re: Interurban PCCs ???


> Does that mean, Boris, that the balancing speed of a PCC motor would be
> around 30 mph on level track with 600 volts.  And it is the weakening of
the
> field that allows the motor speed to increase to propel a PCC car to
around
> 42 mph??  In other words, at what track speed would the back EMF equal
> applied force without field shunting??  And with field shunting???
>
> John