United StatesTransformer Frequency
What is Transformer Frequency
The three common frequencies available are 50Hz, 60Hz and 400Hz. European power is typically 50Hz while North American power is usually 60hz. The 400 Hz is reserved for high-powered applications such as aerospace and some special-purpose computer power supplies and hand-held machine tools. Such high frequencies cannot be economically transmitted long distances, so 400 Hz power systems are usually confined to the building or vehicle.The transformer cannot change the frequency of the supply. If the supply is 60Hz, the output will also be 60 Hz. In most parts of the Americas, it is typically 60Hz, and in the rest of the world it is typically 50Hz. Places that use the 50 Hz frequency tend to use 230 V RMS, and those that use 60Hz tend to use 117 V RMS.
The frequency of large interconnected power distribution systems is tightly regulated so that, over the course of a day, the average frequency is maintained at the nominal value within a few hundred parts per million. While this allows simple electric clocks, relying on synchronous electric motors, to keep accurate time, the primary reason for accurate frequency control is to allow the flow of alternating current power from multiple generators through the network to be controlled.
Frequency of the system will vary as load is added to the system or as generators are shut down; other generators are adjusted in speed so that the average system frequency stays nearly constant. During a severe overload caused by failure of generators or transmission lines, the power system frequency will decline. Loss of an interconnection carrying a large amount of power (relative to system total generation) will cause system frequency to rise. Special protection relays in the power system network sense the decline and may automatically initiate load shedding or tripping of interconnection lines, to preserve the operation of at least part of the network. Quite small frequency deviations, on the order of 0.5 Hz on a 50 Hz or 60 Hz network, will result in automatic load shedding or other control actions to restore system frequency. Smaller power systems, not extensively interconnected with many generators and loads, may not maintain frequency with the same degree of accuracy.
50 Hz vs. 60 Hz Power Transformers
More iron and/or more turns of wire are required to have the same transformer winding inductive reactance at a 50Hz frequency. As a result, power transformers designed for use in U.S. 60Hz applications run very hot, and sometimes extremely hot, if used in 50Hz power mains, even if they have windings to accommodate the higher voltages. Iron-core and copper-wire both cost money and take physical space, so transformer designers generally use no more of either than necessary to keep power losses reasonable at an intended operating frequency.One of the most common questions is "what will happen if I plug my 60Hz dryer, heater into a 50Hz outlet?" The most likely answer is "it depends." If the appliance is not motorized, there may be no noticeable affect. Otherwise:
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What happens if you connect a 60Hz motor to a 50 Hertz mains:
- The motor turns 17% slower
- The internal current goes up by 17%
- The power (watt) goes down with 17 %
- The mechanical cooling is less, because of 17% less turns
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