Converting 110 volt to 220 v (single phase) with transformer .... ok idea ? - Page 2
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  1. #21
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    Quote Originally Posted by SomeoneSomewhere View Post
    Ah, I meant the motor expected 60Hz or 50hz specifically. Not the transformer. I agree that transformers generally don't care.

    I just mean that a VFD doesn't just throw a different frequency at the same voltage; it varies both voltage and speed together. So saying "well, a VFD can make the motor run at 30Hz just fine, so running a 60Hz 230V motor at 50Hz 230V must be fine" is a bit of a false equivalence.

    When a VFD is programmed for a 230V 60Hz motor, and told to drive it at 30Hz, it will reduce the voltage proportionately down to 115V; hence the term 'V/Hz' - the ratio of voltage to frequency remains constant. Special modes like low-end torque boost, parabolic V/Hz, and vector modes are different but you will still see less voltage at lower speed. I'm pretty sure you already know that, though.
    Over-thinking it.

    MOST motors are NOT run right at their ragged-edge of performance.

    Warranties eat too-slender margins when they are. "Bean counters" have a LOUD voice in the choice. Long time ago, Engineers had to BECOME "bean counters" same as if they had been born Accountants.

    Life-cycle costs are lower to have some reserve. So they have it.

    MANY motors are optimized in Iron and Copper @ 55 Hz.
    Of course they will obey Hz for RPM.

    But when making hundreds of different models "already", why ALSO double the SKU number of your major components when 5 Hz either way isn't that big of a deal, otherwise?

    Commodity motors JFW on either service.

    Uber-efficient, bespoke purpose, designed-in for particular advantage, or otherwise "bleeding edge" are whatever the tasking needs them to be, and change is fast-moving. Cordless especially.

    That might include rather low-priced corded OR cordless hand tools or kitchen-counter appliances BUT.. the VOLUME .. is insanely high compared to machine-tool motors.. and easily justifies "custom" optimization.

    End of any given day?

    It's always "all about the money".

    And H.R Herz was a physicist. Not a banker.


  2. #22
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    Quote Originally Posted by thermite View Post
    Over-thinking it.

    MOST motors are NOT run right at their ragged-edge of performance.

    Warranties eat too-slender margins when they are. "Bean counters" have a LOUD voice in the choice. Long time ago, Engineers had to BECOME "bean counters" same as if they had been born Accountants.

    Life-cycle costs are lower to have some reserve. So they have it.

    MANY motors are optimized in Iron and Copper @ 55 Hz.
    Of course they will obey Hz for RPM.

    But when making hundreds of different models "already", why ALSO double the SKU number of your major components when 5 Hz either way isn't that big of a deal, otherwise?

    Commodity motors JFW on either service.

    Uber-efficient, bespoke purpose, designed-in for particular advantage, or otherwise "bleeding edge" are whatever the tasking needs them to be, and change is fast-moving. Cordless especially.

    That might include rather low-priced corded OR cordless hand tools or kitchen-counter appliances BUT.. the VOLUME .. is insanely high compared to machine-tool motors.. and easily justifies "custom" optimization.

    End of any given day?

    It's always "all about the money".

    And H.R Herz was a physicist. Not a banker.

    For 240V, sure. For 480V they are optimized for 60hz.

  3. #23
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    Quote Originally Posted by Strostkovy View Post
    For 240V, sure. For 480V they are optimized for 60hz.
    *yawn*

    "THEY?" Siemens been told that?

    What's your explanation for 400 Hz motors?

    Ever wonder that that eerie WHINE is on passenger electric rail as the string of cars comes off-rest?

    Some fool Asian Engineer not "get the memo"?

    Stuff is "optimized" for whatever it NEEDS to be "optimized" to do well.

    Semantics thing. Not just Engineering. Nor even ALWAYS "money".

    See SR-71. F-22 Raptor.

    ;D

  4. #24
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    All this verbiage over a simple problem.

    Transformers do care what frequency they are run at because the cycle time determines the time the flux has to approach saturation. The other factor determining the degree of saturation is voltage. You can run a 50 cycle transformer at 60 cycles at the same or a little higher voltage. Running a 60 cycle transformer at 50 requires lowering the voltage.

    Transformers made for service like 120 to 240 will have the turns ratio adjusted to make up for the inevitable losses. Most don't and it usually does not cause hardship.

    Typical power line transformers have two 120 volt windings and two 240s. By seriesing or paralleling windings you can set it up for 120, 240 or 480 and input or output and higher voltages as an autotransformer. In the shop I have three 15 KVA transformers connected for 120/208, 240, and 480, three phase, all on wall outlets so I just plug into the voltage I need. Since in some cases I am only using one of a pair of windings, I can only use 7.5 KVA from each transformer for 22.5 KVA total from the three, but I never need that much. Such transformers are common in many KVA ratings.

    If you run a 50 cycle induction motor on 60 cycles, it will run about 20% faster and be happy. If you run a 60 cycle motor on 50, you will have to reduce the voltage or it will draw too much current.

    That's about the size of it. I would look for a transformer with two 120 volt windings or a center tapped 240 and run it as an autotransformer because the losses are smaller and you can get by with a smaller unit.

    Bill

  5. #25
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    Quote Originally Posted by 9100 View Post
    All this verbiage over a simple problem.

    Transformers do care what frequency they are run at because the cycle time determines the time the flux has to approach saturation. The other factor determining the degree of saturation is voltage. You can run a 50 cycle transformer at 60 cycles at the same or a little higher voltage. Running a 60 cycle transformer at 50 requires lowering the voltage.

    .......
    Typical power line transformers have two 120 volt windings and two 240s. By seriesing or paralleling windings you can set it up for 120, 240 or 480 and input or output and higher voltages as an autotransformer. .......... Such transformers are common in many KVA ratings.

    If you run a 50 cycle induction motor on 60 cycles, it will run about 20% faster and be happy. If you run a 60 cycle motor on 50, you will have to reduce the voltage or it will draw too much current.

    That's about the size of it. I would look for a transformer with two 120 volt windings or a center tapped 240 and run it as an autotransformer because the losses are smaller and you can get by with a smaller unit.

    Bill
    You are describing the classic "4-way" transformer that I mentioned above. Available from 500 VA up. Lots of sizes, available widely.


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