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    reason for 50 Hz ac current

    hi,

    how did engineers decided to use AC electricity of 50 Hz frequency for homes? why not any other value ? what if we change frequency to some other value say 75 Hz or 100 Hz ?
    will it have any side effect ?


    thanks

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    Re: reason for 50 Hz ac current

    Half the World uses 60Hz and some places use DC.
    All are compromises, lower frequency means generators in power stations turn slower and so last longer, higher frequecies have more losses in distribution. Somewhere below 100Hz is optimal and 50 or 60 were chosen as convenient values. DC is used in some remote places but the inability to step-up and step-down with transformers limits the distance it can be carried.

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    Re: reason for 50 Hz ac current

    Quote Originally Posted by betwixt View Post
    Half the World uses 60Hz and some places use DC.
    All are compromises, lower frequency means generators in power stations turn slower and so last longer, higher frequecies have more losses in distribution. Somewhere below 100Hz is optimal and 50 or 60 were chosen as convenient values. DC is used in some remote places but the inability to step-up and step-down with transformers limits the distance it can be carried.

    Brian.
    >>>>> power stations turn slower and so last longer

    so why we have not decided to use much lower values say 30 Hz ??? what if i use 30 hz ac with a supported 30 hz electric led. will bulb not glow ? will it fluctuate ?



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    Re: reason for 50 Hz ac current

    Here in the US we have 60 Hz. It's easier to calculate and build gear mechanisms to drive clocks (60 seconds per minute, 60 minutes per hour, 12 hours on a clock face). 60 is evenly divisible into thirds and quarters.

    When making low voltage power supplies, a 60Hz step-down transformer can be less bulky than one made for 50Hz, and ripple frequency is higher at the smoothing capacitors, allowing lower Farad values.



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    Re: reason for 50 Hz ac current

    what if we change frequency to some other value say 75 Hz or 100 Hz ?
    How, running your own electricity plant? Reworking all applicances designed for 50 respectively 60 Hz?

    so why we have not...
    Admit, you are just guessing

    If you want a substantiated answer, you can review the introduction chapters of Electrical Power Engineering text books. Or read a summarizing article on Wikipedia like https://en.wikipedia.org/wiki/Utility_frequency



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    Re: reason for 50 Hz ac current

    Instead,

    so why would have...
    There is currently a plethora of equipment which extracts samples from the network mains in order to synchronize their PLLs (e.g UPS, TV, etc...), and therefore however much the 50/60Hz values have been arbitrated based on the current circunstances or material tecnologies available when it was decided more than a century ago, switching to any other value would have an impact in a chain of products and systems. In short, will not have an absolute answer as to the why of 50/60Hz, as for every aspect there will be pros and cons to increasing or decreasing that frequency.
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    Re: reason for 50 Hz ac current

    Quote Originally Posted by FvM View Post
    Or read a summarizing article on Wikipedia like https://en.wikipedia.org/wiki/Utility_frequency
    Great link, thank you!

    More examples on unusual frequency: here in Germany, railway for historic reasons use 16.7 Hz instead of the usual 50 Hz, because in the early days high power electric motors where easier to design for lower frequency. To my knowledge, they even operate some special power plants for that frequency.



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    Re: reason for 50 Hz ac current

    16.7 (nominal 50/3) Hz is central European standard used in Austria, Germany, Norway, Sweden, Switzerland since early- 20th century. German railway power supply has about 3 GW installed power (as of 2000) with a national 16.7 Hz grid, supplied by a combination of dedicated power plants, static and rotating converters and links to Austria and Switzerland. See Andreas Steimel, Electric Traction - Motive Power and Energy Supply, 2nd issue 2014 (Elektrische Triebfahrzeuge und ihre Energieversorgung)



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    Re: reason for 50 Hz ac current

    another reason for AC is it means relays get less damage from switching....eg, a relay for 250vac would only handle switching 30vdc

    >60hz means there is too much stray capacitve coupling from the mains
    <50Hz means transformers have to be too big.

    - - - Updated - - -

    also skin effect losses get too high if >60hz

    - - - Updated - - -

    core losses in mains supply system transformers get too high if >60hz

    - - - Updated - - -

    in the old days, 50hz was chosen because in incandescant light bulbs the flicker cannot be seen



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    Re: reason for 50 Hz ac current

    The main reason for commercial power 50/60 Hz was chosen and not a lower frequency is twofold:

    -Lamp flicker and radio hum. Lower frequency ripple requires larger filter components.
    -The transformer size increases significantly with lower frequency.

    Having said this; The lower frequency helps electrical traction motors to operate more efficiently.
    As previously explained, that is the reason electrical railways have their dedicated power lines at a lower frequency.
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