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The induction motor was found to work well on frequencies around 50 to 60 Hz, but the materials available in the 1890s would not work well at a frequency of, say, 133 Hz. There is a fixed relationship between the number of magnetic poles in the induction motor field, the frequency of the alternating current, and the rotation speed; so, a given ...
The 50 Hz (60 Hz in North America) AC grid was already established at the beginning of the 20th century. Although series-wound motors can in principle run on AC as well as DC (the reason they are also known as universal motors ) large series-wound traction motors had problems with such high frequencies.
Mains hum, electric hum, cycle hum, or power line hum is a sound associated with alternating current which is twice the frequency of the mains electricity.The fundamental frequency of this sound is usually double that of fundamental 50/60 Hz, i.e., 100/120 Hz, depending on the local power-line frequency.
Other three-phase voltages, up to 830 volts, are occasionally used for special-purpose systems such as oil well pumps. Large industrial motors (say, more than 250 hp or 150 kW) may operate on medium voltage. On 60 Hz systems a standard for medium voltage equipment is 2,400/4,160 V whereas 3,300 V is the common standard for 50 Hz systems.
Some lines in the United States have been electrified at 12.5 kV 60 Hz or converted from 11 kV 25 Hz to 12.5 kV 60 Hz. Use of 60 Hz allows direct supply from the 60 Hz utility grid yet does not require the larger wire clearance for 25 kV 60 Hz or require dual-voltage capability for trains also operating on 11 kV 25 Hz lines. Examples are:
An induction generator produces electrical power when its rotor is turned faster than the synchronous speed.For a four-pole motor (two pairs of poles on stator) powered by a 60 Hz source, the synchronous speed is 1800 rotations per minute (rpm) and 1500 RPM powered at 50 Hz.
This is because as long as the motor torque is constant, I 2 R or winding resistance losses are the same at 50 Hz and 60 Hz. The motor output power, however, increases linearly with speed, increasing by 20% when the frequency is increased from 50 Hz to 60 Hz. In general, the 60 Hz efficiency is about 2.5% to 0.5% greater than the 50 Hz values.
Converted in 1978 from Pennsylvania Railroad 11 kV 25 Hz system to the 12.5 kV 25 Hz on the Rahway-Matawan ROW and 12.5 kV 60 Hz electrification extended to Long Branch in 1988. The Matawan-Long Branch voltage converted from 12.5 kV 60 Hz system to the 25 kV 60 Hz in 2002. New Haven to Boston: Northeast Corridor (NEC), Amtrak