15 kV AC railway electrification
The 15 kV, 16.7 Hz AC railway electrification system is used in Germany, Austria, Switzerland, Sweden and Norway. The high voltage enables high power transmission with the lower frequency reducing the losses of the traction motors that were available at the beginning of the 20th century. Railway electrification in late 20th century tends to use 25 kV, 50 Hz AC systems which has become the preferred standard for new railway electrifications but extensions of the existing 15 kV networks are not completely unlikely.
Due to high conversion costs, it is unlikely that existing 15 kV, 16.7 Hz systems will be converted to 25 kV, 50 Hz despite the fact that this would reduce the weight of the on-board step-down transformers to one third that of the present devices.
History
The first electrified railways used series-wound DC motors, first at 600 V and then 1,500 V. Areas with 3 kV DC catenaries (primarily in Eastern Europe) used two 1,500 V DC motors in series. But even at 3 kV, the current needed to power a heavy train (particularly in rural and mountainous areas) can be excessive. Although increasing the transmission voltage decreases the current and associated resistive losses for a given power, insulation limits make higher voltage traction motors impractical. Transformers on each locomotive are thus required to step high transmission voltages down to practical motor operating voltages. Because transformers require alternating current (AC), high voltage electrified railways adopted AC along with the electric power distribution system (see War of Currents).
Podcasts:
Key Of C
by: Cory LeeI really can't remember why
Why I loved you
I really can't remember when
When I gave a care
Everytime I think of you
You keep on fading
And everytime I hear your name
I feel nothing deep inside
I know that your callin
I know that your tryin to change my mind
Anyway that I sing it
It is still the same
Your a G out of key
And one note remains
In the key of C
I don't give an F about you
Anyway that I sing it
It is still the same
Your a G out of key
And one note remains
In the key of C
I don't give an F about you
I really can't remember why
Why I need it
I really can't remember how
How you layed me down
Now you seem to come around
Uninvited
But you don't seem to understand
Or even hear my words
I could sing acapela
Or do re mi fa
With an orcastra
You won't change my tune
Anyway that I sing it
It is still the same
Your a G out of key
And one note remains
In the key of C
I don't give an F about you
Anyway that I sing it
It is still the same
Your a G out of key
And one note remains
In the key of C
I don't give an F about you
Oh (oh) I know (know)
Let go (let go, let go)
Sitting in the key of C
Oh (oh) I know that your missin me
Let go (let go, let go)
(Sitting in the key of C)
I could sing acapela
Or do re mi fa
With an orcastra
You won't change my tune
Anyway that I sing it
It is still the same
Your a G out of key
And one note remains
In the key of C
I don't give an F about you
Anyway that I sing it
It is still the same
Your a G out of key
And one note remains
In the key of C
I don't give an F about you
And you keep on tryin to call me
And I see that you are lonely
In the key of C (key of C)
I don't give an F about you
After all the lies and games
Heres my note and my note remains
In the key of C