Power systems operating frequencies


Thread Starter


Been enjoying your blog...I maintain emergency engine generators here at our regional airport,so any info on power systems interests me!

So while I was in Japan in the US Navy I got to ride the Bullet train there. What a ride! Naturally I was fascinated by the power system & started studying other bullet train systems mainly Europe's. So why do some European railway power supply systems use 16 2/3 HZ frequency??? (not 50HZ) Some even use 25 HZ.



The basic reason is that early 'analogue' electric motors had slow 'dynamics', thus requiring low-frequency AC (or DC) for the power supply. Wikipedia in:


explains it as "Common DC commutating electric motors can also be fed with AC (universal motor), because reversing the current in both stator and rotor does not change the direction of torque. However, the inductance of the windings made early designs of large motors impractical at standard AC distribution frequencies. In addition, AC induces eddy currents, particularly in non-laminated field pole pieces, that cause overheating and loss of efficiency."

Once thyristors and other more modern power conversion equipment came along, this restriction became obsolete and railways started using 50/60 Hz on new systems, and when replacing older systems.

If you are interested, I am sure I have some books that give more details, or a proper electrical engineer (I am a mathematician with an interest in railways) may be able to give more complete/accurate reasons.