Re: Techie Question

Cathode Ray <RBCatlow@xxxxxxx> wrote:

I still can't understand why 66's soldier on with DC series wound
traction motors when their manufacturer (EMD) almost exclusively uses
three phase AC induction motors for the North American market with
their inherent advantages and improved perfromance.

Actually, the sales of DC traction and AC traction locomotives in North
America are about even, in terms of the number of locomotives delivered.
EMD, in particular, was not able to sell many AC traction locomotives at
all for a number of years, and solely made DC traction locomotives. It
has only been recently that their AC traction business has picked up
again.

The decision on what type to purchase is an economic one, considering the
life cycle cost of the locomotive. Since the purchase price of AC
traction locomotives is significantly higher, the railroads only purchase
them where they need the extra tractive effort available from their
highly refined control system.

Where the tractive effort offered by DC traction is adequate, they will
save money by buying the less expensive design. The savings in traction
motor maintenance with AC motors has not been sufficient to repay the
higher initial cost of the locomotives without also gaining savings
through reduced fleet size.

An example was the Union Pacific purchase of about 1,200 DC traction
locomotives a just few years ago, which was the largest ever purchase
order that EMD received. The locomotives were intended to provide a
general purpose locomotive that could replace older locomotives at
essentially a one-to-one ratio in lower mileage services. At the same
time, UP was also purchasing AC traction locomotives that were destined
to heavy haul services. In these heavy haul services, they anticipated a
reduction in the fleet size as a result of needing fewer locomotives per
train. Thus one railroad purchasing the two types of locomotives for
different services.

As far as the Class 66 locomotives are concerned, EMD had delivered AC
traction locomotives with heavier axle loads to places like Queensland,
so it isn't as though they are unwilling to offer such locomotives to the
export market. I suspect the problem isn't that EMD doesn't offer such
locomotives in the European market, but that nobody wants to pay the
premium required for such a locomotive when loading gauge, axle load
limitations, and safety cases are considered.

.