(erielack) Transition

["JOHN J BOEHNER" <jjbchian_@_msn.com>]

Listers,

Mike has done an excellent job of explaining "transition". The EL guys all said they liked the ALCO RS Road Switchers as they had to "shift them", which means manual transition. Early EMDs could be operated in "Manual" or "Automatic". Automatic transition us usually around 18 MPH. 

When starting a commuter train, there was nothing that could compare to the RS-3, they could really accelerate! 

JJBoehner 





From Archives_@_Railfan.net<about:blank>
Message-ID: <892666.41522.qm_@_web31612.mail.mud.yahoo.com<about:blank>> 
In-Reply-To: <461173BD.9070601_@_verizon.net<about:blank>>
Date: Tue, 3 Apr 2007 08:44:58 -0700 (PDT)
From: Mike Spinelli <idrsspin_@_yahoo.com<about:blank>>
Subject: Re: (erielack) Re: Transition

Basic electricity. You have CURRENT and VOLTAGE. If
you think of a hose, the current is the amount of
water going through it, and the voltage is the
pressure it's under.

Current gives you torque. Think of a water wheel that
needs a lot of water to get moving. Voltage gives you
speed. Once moving the pressure of the water will make
the wheel turn faster. If you could put a bunch of
water on the wheel paddles at first, it'll start
easier. As it  gets going good, if you could increase
the pressure (even if decreasing the amount of water),
it'll be better for your top speed.

(Maybe not a good analogy, but it's the best I can
come up with after only 2 cups of coffee LOL)
 
Traction motors start out in series. The motors all
get full CURRENT, providing low speed torque. The
voltage is divided between the motors.

As speed increases, the motors are switched or
"transitioned" from series to parallel. In parallel,
the motors all get full VOLTAGE, the current is
divided among all of the traction motors. This is
better for high speed running.

They don't all jump from series to parallel at once,
there are different sequences of different
combinations depending on the speed. This may be where
manual transition didn't work. It either went full
series to full parallel all at once, or it was too
hard to figure where to set it for a given load and
speed. Alco may have thought that it's operation was
close enough to the old Johnson Bar on the steam
engines and the engineers could become adept at using
it in a similar way.

In electricity, SHUNTING means something much
different, and I can't think of it being used in the
generator-tracion motor circuit.

      Mike Spinelli


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