[PRCo] Re: Polarity

[Jim Holland]

Another thought:
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The 3-wires in Cin DO amount to Polarity Reverse.
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I-F the hot is the curb wire under normal operation, then the TrolleyCar 
on the oeft side 2 wires of the 3-wire system has the hot in the left 
side pole!!!       If the center of the 3 wires is hot, then one of the 
two sets of overhead is polarity reversed for the TrolleyCar sitting 
under it.
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So the Cincy PCCs had to be able to accommodate polarity reverse in the 
OH.       And somewhere out of view the polarity is reversed in the 
overhead  --  Possibly at the X-Ings of the two lines were insulators 
would be needed anyhow  --  need to think about this some more!!!
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Jim___Holland
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Jim Holland wrote:

> Clarifying Words added in [CAPS] in Brackets!!!!!!!
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> Jim Holland wrote:
> .
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>> The 'Principle' behind reversing the motor on a PCC is what Fred
>> described -- dassn't work like models where we simply reverse the
>> polarity because models use permag motors while prototype have field
>> wound motors -- [SIMPLY] reversing [OVERHEAD] polarity on the
>> prototype reverses both commutator and field without a change in
>> direction!! But I am preaching to the Choir here -- you know
>> that. Think this is the point where the two wires were minus an
>> insulator and you and Fred shorted out!
>> .
>> But for the Average TrolleyCar there wouldn't be the need to switch
>> polarity -- Don't Want Positive In The Rails!!! -- so there shouldn't
>> be a need to protect against polarity reverse in the overhead wire -
>> singular! But where TrolleyCars share overhead with TCs o-r where
>> TrolleyCars are equipped with dual poles, the 'possibility' of
>> polarity reverse in the overhead wires does exist.
>> .
>> SF-Muni TrolleyCars share some TC overhead but nothing complicated and
>> nothing where polarity reverse would be any problem -- only have 2 or
>> 3 such locations in the TC overhead where polarity is reversed and
>> these are far from TrolleyCar tracks.
>> .
>> ETI's Do Operate through polarity reverse sections -- must be
>> something common to Trolley Coaches so the ETI's are protected against
>> this.
>> .
>> I-F Sparky (Robert__"S"__Parks!) hasn't changed his website, here is a
>> photo of polarity reverse in TC overhead at Union and Fillmore in SF:::
>> .
>> Interesting, if you care to follow the current paths. The third image
>> shows the interesting jumper arrangement used to get 600V to the
>> curbside wire.
>> .
>> Overview image (attached):
>> .
>> http://www.sfmuni.net/overhead/070105-120517-Union-Fillmore-fr5491-ReversedPolarityOverhead-E-lg.jpg
>> .
>> Leading switch:
>> .
>> http://www.sfmuni.net/overhead/070105-120529-Union-Fillmore-fr5491-ReversedPolarityOverhead-E-lg.jpg 
>>
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>>
>> .
>> Trailing switch:
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>> http://www.sfmuni.net/overhead/070105-120544-Union-Fillmore-fr5491-ReversedPolarityOverhead-SE-lg.jpg 
>>
>>
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>> .
>> Robert Parks
>> .
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>> .
>> Jim___Holland
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>> .
>> .
>> Boris Cefer wrote:
>> .
>>
>>> I am aware some PCC equipment with "variable polarity". I have to
>>> look whether my books contain any such diagrams and what that
>>> "variable polarity" means in the term of function.
>>>
>>> Semiconductor propulsion is far more sensitive on polarity. Unless
>>> there is a sophisticated system that allows automatical polarity
>>> conversion, it can't work. If there are experts on electrical
>>> engineering in relation to transit, each comment is welcome!
>>>
>>> B
>>>
>>> ----- Original Message -----
>>> From: "Jim Holland" <prcopcc at p-r-co.com>
>>>
>>> ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
>>>
>>>> .
>>>> VERY___Interesting your comments about polarity and the PCC -- the
>>>> Muni older Flyer TCs were simple beasts but the electronic ETI's are
>>>> more PCC-esque and I wonder about polarity reverse in relationship
>>>> to them. We do still have some overhead like that here in SF; we
>>>> just had a discussion about same on the SFMuniHistory list!!!
>>>> .
>>>> Now, Lettuce see if this goes through -- And When -- If-Ever!!!
>>>> .
>>>> .
>>>> .
>>>> Jim___Holland
>>>
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