Although ac traction motors are emerging for very heavy drag service, particularly in western North America, and its supply of Powder River Basin coal to other areas of the U.S., the simpler dc traction motor system remains the most popular, with Union Pacific alone having over 1,500 current model SD70Ms with dc traction motors (plus an additional 1,000 SD70MACs with ac traction motors).
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After 1891, polyphase alternators were introduced to supply currents of multiple differing phases.
Alternator | alternator |
When commissioned in 1912, the station had two John Musgrave & Sons steam turbines of the Zoelly impulse type, each driving a Siemens Brothers 2,000kW alternator, generating a three-phase output of 6,000V at 50Hz.
The station was originally equipped with two turbo-alternators rated at 7.2 megawatts (MW), made by AEG of Germany, and two turbo alternators rated at 6.25 MW and 13.2 MW, made by Brown Boveri of Switzerland, for a total generating capacity of 33.85 MW.
When the core is subjected to a changing magnetic field, as it is in devices that use AC current such as transformers, inductors, and AC motors and alternators, some of the power that would ideally be transferred through the device is lost in the core, dissipated as heat and sometimes noise.
Modules are available for brushless permanent magnet motors (BPM), outer rotor BPM motors, induction motors, permanent magnet dc machines, switched reluctance motors, synchronous machines and claw pole machines.
After a strong early showing in the race in which Francevic had held 2nd for some time behind early leader Tom Walkinshaw, a failed alternator diode put them many laps down.
Owing to the delay of the third Dick, Kerr unit, a single Curtis 7.5 MW turbo-alternator from General Electric of Schenectady, New York, USA was brought into temporary use in 1917 in the unit number four position.