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230V 50Hz to 110V 60Hz (I've read the others!)

  1. Sep 2, 2014 #1
    Hello everyone! I'm new to the forum so please forgive me if I've messed something up.

    My question is as follows:

    I need to generate a 110V 60Hz power supply (as used in the US) from 230V 50Hz. It's for some old electronics that rely on the 60Hz AC for timing, so I promise you I can't get away with 110V 50Hz :)

    Would it be possible to convert 230V 50Hz to 12V DC using a 12V battery charger with a high amp rating (something like 40A) and connect that directly to an everyday inverter that would give me 110V 60Hz? Originally I planned on charging up a few batteries this way then running the inverter off those for a while, but I was curious if I could skip the batteries altogether, just so long as I don't draw too much current from the battery charger. I don't have motors or anything that is going to suddenly draw a large amount of current.

    Essentially it would look like this...

    Australian GPO (Out: 230V 50Hz) --> Car battery charger (Out: 12VDC 40A) --> Inverter (Out: 110V 60Hz)

    Does this sound like a feasible solution? Obviously it wouldn't be able to run for extended periods of time due to overheating and whatnot (particular if I get cheap eBay-grade gear) but perhaps for a couple hours every now and again? I thought I'd ask the forum before I went out and bought anything just to confirm. I've added my ramblings at the very bottom of the post for someone to read through and undoubtedly find a fault in. Please let me know :)

    Thanks so much in advance!
    Abe.


    I need at most 250 watts of power for my 110V 60Hz appliance.
    I have 230V 50Hz connected to a battery charger that now supplies 12V 40A. This guy is around 85% efficient so I'm getting around 400 watts of power. I then connect that to my inverter which is also around 85% efficient and rated for 500 watts. So I could potentially draw 340-ish watts from my final outlet (at the very best).
     
  2. jcsd
  3. Sep 2, 2014 #2
    An old computer power supply might do the trick in place of the battery charger. And it would avoid any issues the charge controller might cause. There are many tutorials for converting an old computer PS into a bench PS.

    Do you need a clean sine wave? Many inexpensive inverters do not have a pure sine wave output.
     
  4. Sep 2, 2014 #3

    NascentOxygen

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    Staff: Mentor

    It's not feasible to construct a low power 60 Hz oscillator to cater for the timing need, and supply the rest with 50Hz 110V?

    No?

    Thought not. :tongue:
     
    Last edited: Sep 2, 2014
  5. Sep 2, 2014 #4

    Averagesupernova

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    Not sure what you timing needs are but I would certainly not count on the frequency of an invertor being as accurate as commercial power.
     
  6. Sep 2, 2014 #5
    As others have said, the signal from the inverter is likely pretty noisy...

    However, your line of thinking is correct - what you described would work if the 60Hz is clean enough for you. The voltage waveform may look more like a mix somewhere between a poor sine wave and a poor square wave. If you go this route, I would still use a battery to help clean up and smooth out the power from the battery charger. Battery chargers are very noisy and do not have filter capacitors so your voltage actually crosses 0V twice per cycle feeding into the rectifier, resulting in 120Hz "pulsed" DC. A large (1F?) filter capacitor or connecting it to a battery will smooth out this pulsing to the inverter - the larger the load, the higher value capacitor that is needed.

    There is one other option... driving a generator/alternator at the appropriate RPM from a motor off the 240VAC 50Hz, the problem is i think you'd need to spin the 60hz generator at a specific RPM, such as either 1800 or 3600 depending on the number of poles, but a motor running on 50Hz would be either 1500 or 3000 rpms, depending on the type of motor, etc...

    Airplanes run on 400Hz 115VAC, there used to be rotary converters used to power on the ground from facility power, basically a 60hz motor turning a 400hz generator, but now you rarely see any and most are solid-state, and most airports now, they don't use ground power carts, they use giant converters installed in the facility - possibly generated on-site from a mechanical generator. Belts can be used to change ratio, but from reading on this site, the magic numbers are 10 and 12; a 10 pole AC motor coupled to a 12 pole generator would do 50hz to 60hz.... google "Product Rotary Motor Generator Belt Coupled" and read up on the first result, at "georator" they claim some of their units can be as high as 90% efficiency at full load! obviously their products are way overkill for you though :)

    What is the mystery device you want to power? Is it resistive? inductive? If you really need precision, the 60Hz inverter may not even be precise enough, it may vary between 58 and 62, or who knows. I have a very cheap inverter at home. If I remember tonight, I'll throw my scope on it and let you know...
     
  7. Sep 2, 2014 #6
    he needs precision :)

    your idea is fine. also you dont have to worry about overheating as long you are below rated power of your mid-circuit equipment. rated power can be delivered constantly, by definition.
     
  8. Sep 3, 2014 #7
    What an overwhelming response, thanks everyone!

    'montoyas7940': I'll definitely consider that. Thank you.

    'NascentOxygen': Do I detect a hint of sarcasm? ;) As you predicted, I don't believe that will work here, no.

    'Averagesupernova': Worst case scenario, if I can get a frequency within +/-2Hz of the 60Hz I'd be satisfied just for very short testing purposes I suppose.

    'mp3car': You suggest running the battery charger into the battery and THEN out into the inverter for stability? I've got a 220V inverter already that is supposedly "pure sine wave" and doesn't look terrible when I run a CRO over it, but I highly doubt I'll find an eBay seller willing to do that for me before I buy! Also, I had considered the generator/alternator situation already but decided against it for now. Perhaps later on I'll think about it again if/when I need precision.

    Regards,
    Abe.
     
  9. Sep 3, 2014 #8
    Ooo, forgot. The mystery devices include a few clocks, old cathode ray-based gear, some vintage computer gear etc. All of which I have either read require AC for timing, or know because they don't operate correctly.

    I've also come across some old Commodore-brand floppy disk drives today which obviously have motors in them. Since they're 60Hz specifically, I'd imagine that they won't read or write correctly at 50Hz. Other bits and pieces have chips like the 6526CIA which again reply on the power frequency for correct operation.
     
  10. Sep 3, 2014 #9

    davenn

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    The 6526CIA can take a 50 Hz or 60Hz TTL input for its internal clocking :smile:

    They don't rely on power freq. just a programmable 50/60Hz TTL signal

    cheers
    Dave
     
  11. Sep 4, 2014 #10
    'davenn': Brilliant, well that solves at least a couple things. Thanks!
     
  12. Sep 4, 2014 #11

    Baluncore

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    A “Variable Frequency Drive”, VFD, or “Variable Speed Drive”, VSD, will generate an accurate programmable voltage at a precise frequency.
    Look on eBay for a low cost unit. Cost new will be about AU$100.
     
  13. Sep 5, 2014 #12
    'Baluncore': Thanks for your answer, that looks like a pretty decent way of achieving what I'm after.

    Do you know if VFDs exist that halve voltage? I can see plenty that double from 110V to 220V but after a quick search I can't seem to find any 220V to 110V. I'll have a more thorough look over the weekend and fire off some emails but it'd be great to hear from you if you know.

    Regards,
    Abe.
     
  14. Sep 5, 2014 #13

    Baluncore

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    Voltage and frequency are usually just programmable parameters.
    It is very easy to program a lower the voltage, but more expensive to raise the voltage.
    You will need to download the instruction manual for your choice of VFD.
    Identify in the manual the register values you must set for 110 V and 60 Hz.
    Often a potentiometer is available as an input, but you probably don't need that facility so program it out.

    You can probably use a three phase unit, but only connect to neutral and one phase.

    The lowest cost units are designed to drive small single phase induction motors. They provide neutral and a single phase, plus a second phase that is shifted to replace the capacitor circuit.
     
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