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Converting frequency on US devices (60Hz - 50Hz)

Discussion in 'General Electronics Chat' started by circuit44, Aug 31, 2017.

  1. circuit44

    circuit44 New Member

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    Hi guys, I need some assistance on using small US devices designed to operate at 60hz. I'm in the UK (50Hz) trying to use US clippers. Because of the frequency difference, the volt transformers alone don't work. The clippers become loud and violently rattle.

    Some say the solution is an AC to 12v DC converter and a DC to AC 110/60Hz car Inverter as seen below.
    http://www.buythebest10.com/wp-content/uploads/2015/09/6101v4Z8YML._SL1000_.jpg




    Are these methods efficient/accurate? I've heard some say that you need a pure sine wave, but most reviews seem good.

    Just needed to make sure. Appreciate any assistance.

    Thanks.
     
  2. Diver300

    Diver300 Well-Known Member

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    The clippers probably won't mind a modified sine wave inverter, but they may be noisier on that than on a pure sine wave one.

    Conversion via 12 V is one of the easiest ways of doing it because both the 230 to 12 V converter and the 12 V to 110 V converter are readily available.

    Efficiency is usually defined as power out divided by power in, and that won't be good if you convert via 12 V, but I don't know if that is important. The cost of electricity will be low on the list of priorities for a set of clippers, as they are quite low power and they probably won't run for long. The efficiency will be poor because there are multiple stages in the conversion. It is probably something like this:-

    12 V power supply:-
    Rectify 230 V rms 50 Hz mains to give DC at 350 V
    Switch 350 V DC on and off at around 30 kHz
    Transform 350 V 30 kHz to around 12 V (peak) 30 kHz
    Rectify 12 V 30 kHz to 12 V DC

    110 V inverter:-
    Switch 12 V DC on and off at around 30 kHz
    Transform 12 V 30 kHz to about 160 V (peak)
    Rectify 160 V (peak) to give 160 V DC
    Switch 160 V (peak) on and off at 60 Hz to give 110 V rms 60 Hz

    As you can see, that is a lot of stages, with power lost at each stage.

    I don't know what you mean about accuracy. The frequency and voltage produced by a cheap inverter won't be very precise, but why would you care for clippers.

    I think that clippers are a rather different device to many, if they are anything like the electric razor my father had. The cutters actually move at the frequency of the mains. The voltage causes current to flow, which causes acceleration of the cutters, so speed builds up, and the cutters move, and that is stopped by the mains voltage reversing and the whole lot happens in the opposite direction, with the process repeating 60 times a second.

    If you run from 50 Hz, there is more time for the current to build up so more current, more time for the acceleration, with a larger current, so much more speed, and then more time for the speed to give distance. It is likely that the noise is the cutter hitting the end stops hard. This could be made worse by a transformer that gives out 120 V or so with a full load, and your clippers are just a small load, and the transformer voltage is higher

    It is common for electrical devices like transformers and motors to work on a lower voltage with 50 Hz than with 60 Hz. In the case of the clippers, you may need to look at a much less, maybe 110*(50/60)^3, or about 65 V if they are to work at 50 Hz. If you do that, the cutters will run more slowly, but you will probably only notice that the pitch of the sound they make is lower.

    You could try something like this:-
    http://uk.farnell.com/multicomp/mcta250-35/transformer-toroidal-2-x-35v-250va/dp/9530800 but that is quite expensive for a test which might not work.
     
    • Informative Informative x 1
  3. Pommie

    Pommie Well-Known Member Most Helpful Member

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    If the clippers state a wattage then use that to calculate a series resister that will drop the voltage to around 100V. So, if the clippers are 20W then they are drawing 20/110 = 2/11 or 0.18A. A suitable resistor would be (110-100)/0.18 0r around 60 to 70 ohms. If it works it's a very cheap solution.

    Mike.
     
  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    My clippers (ancient, Wahl brand) work like the razor Diver mentions and have an adjuster (small 'dial' on the side, with a screwdriver slot) to set the oscillation amplitude. Do yours?
     
  6. crutschow

    crutschow Well-Known Member Most Helpful Member

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    The clipper "motor" may be designed to resonant around 60Hz, and thus the improper operation at 50Hz.
    If so, you will have to go the 60Hz inverter route.
     
  7. BobW

    BobW Active Member

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    Yes these clippers are designed to have a mechanical resonance at 60Hz. The amplitude adjustment that alec_t mentions is in fact a spring tension adjustment. Unfortunately, it's fairly fine adjustment, and wouldn't be able to tune the resonance down to 50 Hz. Might be theoretically possible to add some additional mass to the armature to lower the resonance, but the simple solution is a 50Hz inverter.
     
  8. crutschow

    crutschow Well-Known Member Most Helpful Member

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    You mean an inverter that generates 60Hz, right?
     
  9. Diver300

    Diver300 Well-Known Member

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    On the Yankee clipper video, the presenter's term for what Hertz measures is "hurtage"

    I just hope that doesn't propagate like the monstrosity that is "wattage" instead of "power"
     
    • Agree Agree x 1
  10. Diver300

    Diver300 Well-Known Member

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    This device http://www.bestekcorp.com/product/power-strip-travel-converter/4-usb-port-with-uk-us-au-eu-plug.html also changes the frequency.

    The plug adaptor for the UK doesn't meet the UK standards, but you could use a better adaptor, or just change the mains lead, which just plugs in and uses a standard C5 connector to the converter.

    That converter works something like this:-
    Rectify 230 V rms 50 Hz mains to give DC at 350 V
    Switch 350 V DC on and off at around 30 kHz
    Transform 350 V 30 kHz to around 160 V (peak)
    Rectify 160 V (peak) to give 160 V DC
    Switch 160 V (peak) on and off at 60 Hz to give 110 V rms 60 Hz

    So it misses out some of the stages that you get with going via 12 V
     
  11. BobW

    BobW Active Member

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    Oops, Yes 60Hz inverter.
     
  12. circuit44

    circuit44 New Member

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    So I went with this set up.

    Converter
    https://www.maplin.co.uk/p/12v-5000ma-car-accessory-socket-ac-dc-power-supply-l25ay

    Inverter
    https://www.amazon.com/gp/product/B06W9NMXVZ/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

    The clippers will only switch on maybe 70% of the time. The inverter red light will often show. I think the issue is converter related as I've since tried another converter (below), matched up the Bestek inverter and the clippers fare even worse. They cut great, when they'd manage to switch on.

    https://www.amazon.co.uk/gp/product/B07125GXGY/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

    I've been warned about 'cheap' converters made in china, so maybe that's the issue. Other than that, I can't think of a reason why this wouldn't work. The converters have more than enough capacity for my devices.

    Any help greatly appreciated.
     
  13. Diver300

    Diver300 Well-Known Member

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    The problem could be that the clippers take more than their rated power for a fraction of a second, to start up.

    Have you tried the inverter when running from a car? Have you tried plugging them in an turning on before connecting the inverter to the 12 V power supply? You could also try turning on and off at the input to the power supply.

    A lot of power supplies like the Maplin one will not support anything more than the rated current, even for short durations, but the car socket will provide as much current as you want for a fraction of a second.

    You could try an NTC inrush limiter like this:-http://uk.farnell.com/epcos/b57237s0330m000/thermistor-ntc/dp/9754229

    If that is in series with the clippers, the inrush current will be reduced.
     
  14. Carolie

    Carolie New Member

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    I just got a bestek power converter as you mentioned. Thanks for your specific explanations. Just learnt a lot.
     
  15. schmitt trigger

    schmitt trigger Active Member

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    I hear that term so much, that it makes my head hurt.
    There are other examples, like saying "replace that resistance, because it is damaged". Resistance is the parameter, resistor is the device which possess that parameter.
     
  16. Carolie

    Carolie New Member

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    Don't know whether it is the sane with the power converter I just saw on Amazon. I'm looking for a power converter 110V to 230V, I'm going to travel in Britain. So should I get another plug adapter? Its UK plug is three-pronged.
     
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  17. Diver300

    Diver300 Well-Known Member

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    That looks like a converter to convert to 230 V. If you are travelling to Britain, that device would be fairly useless, as it would replicate the sockets that are everywhere.

    What country are the appliances you want to use from?
     
  18. hyedenny

    hyedenny Member

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    Why spend $40 (or more for a power supply or inverter) when you can buy a new clipper for under $20? It seems like a waste of time to even talk about it!
     

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