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  1. #61
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    Gerbil I am not even sure you would need an autotransformer.. US three phase is 207V but they people who make their own phase converters use the 240V connected to their houses and their three phase motors run alright.

    Their voltage are 110, 207, 240. Similar to ours at 240, 415, 480.

  2. #62
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    I run all my 415V 3 phase motors from a hybrid static/rotary phase converter running 480V (i.e. no transformer) and have not had any issues with motor overheating or failure.

    I also can easily start a 5-7HP load from with a 3HP "idler" (it's actually my dust collector motor), however this could be because the dusty's fan is quite heavy (maybe 10 or so kg's) and it acts as a flywheel.
    Cheers.

    Vernon.
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  3. #63
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    How do you reckon I would go running 3 phase welders off 480 volt single phase?

    Many '3 phase' welders are really single phase welders - they use 2 legs of a 3 phase supply.

    Spaznet (SP Ausnet) reckon that my 2 phase supply will actually be closer to 460 volt across phases. My Transtig will run on 2 legs of a 440 volt supply (some of the bars on the input terminals will need to be moved around according to the manual), and when I checked with CIG they reckon that 460 volt will be okay because most electrical equipment is designed to handle a 10% tolerance in supply.

    Question is, is there an issue with with running a welder (or motor for that matter) off a power source with different phase angle (120 deg for 3 phase versus 180 deg for 2 phase)?

  4. #64
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    I'm not an electrical engineer .... but ....

    A welder (single phase, be it 240, 415, 480, or whatever) works on the the voltage placed across the primary of the transformer and as such is not phase angle sensitive.

    Motors on the other hand (and this is where I get a little more sketchy) do have some reliance on phase angle. That said, the use of split phase (i.e. 180º phase shift) to run a phase converter (which subsequently runs said motor) is common practice and from what I have experienced, does not cause any issues with overheating, failure, excessive vibration, etc.
    Cheers.

    Vernon.
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  5. #65
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    This is quite a learning curve for myself.

    As best I understand there are three ways to run 3 phase motors from single phase power supply.

    1) Rotary motor method
    2) Transformer method
    3) A phase changer (professional model)

    The last method do not really understand is it like an inverter welder that uses some sort of circuit board (using the term IGBT what ever that means) rather than a old transformer.

    I'm not sure if the link below is something similar.

    Although it does not put out more than 240v.

    "http://cgi.ebay.com.au/3-7KW-5HP-Brand-New-single-three-phase-VSD-/280390763825?cmd=ViewItem&pt=AU_B_I_Electrical_Test_Equipment&hash=item4148978531[/URL]"

    Two questions
    Are there other methods of powering 3 phase from single phase?

    What exactly is the third method?

    Thanks

    Pulpo

  6. #66
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    Quote Originally Posted by Pulpo View Post
    This is quite a learning curve for myself.

    As best I understand there are three ways to run 3 phase motors from single phase power supply.

    1) Rotary motor method
    2) Transformer method
    3) A phase changer (professional model)

    The last method do not really understand is it like an inverter welder that uses some sort of circuit board (using the term IGBT what ever that means) rather than a old transformer.

    I'm not sure if the link below is something similar.

    Although it does not put out more than 240v.

    "]http://cgi.ebay.com.au/3-7KW-5HP-Brand-New-single-three-phase-VSD-/280390763825?cmd=ViewItem&pt=AU_B_I_Electrical_Test_Equipment&hash=item4148978531[/URL]

    Two questions
    Are there other methods of powering 3 phase from single phase?

    What exactly is the third method?

    Thanks

    Pulpo
    The commercial "Phase Changer" is nothing more then a rotary phase converter..

    It comes in both 240V and 480V models... The 240V has a step up transformer that firstly changes the voltage to 415V... It then makes three phase the same as every other rotary phase converter out there... The difference is most rotary phase converters only have one set of capacitors and are only balanced when one particular load is applied...By balanced I mean the voltages between phases are close to one another...

    The "Phase Changer" is different by having seven sets of capacitors and the voltages are monitored by electronics... When different loads are applied it will vary what capacitors are switched on and off to try to keep the phase to phase voltages the same...

    With the simple single capacitor rotary units if you are running say a 2hp motor and at that the voltages between phases are say 415, 400, 410.. If you switch on a 7.5hp motor the voltages will change to maybe 415, 360, 430, this is because the single capacitors can only balance the voltage at one particular load, which when you build it you work out by putting in different value capacitors.

    While with the phase changer when you switch on the 7.5hp motor it is just like you manually switching over to a different set of valued capacitors, except the machine does it automatically via electronics, and thus the voltage is restored to a semi balanced state... No phase converter will give you 415, 415, 415 between voltages, there is always a difference...


    One phase to phase voltage will always be 415V as this is the phase that originates at the power station.

    There is another company in WA making rotary phase converters as well... I could not follow there website back when I was looking so went with the victorian company..

    The only other method to create three phase is by a static phase converter...This is a solid state electronic device that you connect to the motor...AFAIK you can only run one motor off a single solid state converter at a time.. I am not sure that these devices change the 240V incoming voltage to 415V either...Some might...

  7. #67
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    A static phase converter is basically just a rotary phase converter, but without the idler motor. So effectively the motor you are starting is and becomes the "idler" motor. You can then start other motors (even bigger HP ones) because you now have a kind of supped up rotary phase converter - i.e. one that can start motors under load, plus you now have an idler motor running.

    The big downside to static phase converters is that you can't run a "non-motor" off them until you have at least one motor running.

    You could have a transformer in a static phase converter to change 240 to 415.
    Cheers.

    Vernon.
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  8. #68
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    Default It all sounds correct except for the last paragraph.

    Quote Originally Posted by .RC. View Post
    The commercial "Phase Changer" is nothing more then a rotary phase converter..

    It comes in both 240V and 480V models... The 240V has a step up transformer that firstly changes the voltage to 415V... It then makes three phase the same as every other rotary phase converter out there... The difference is most rotary phase converters only have one set of capacitors and are only balanced when one particular load is applied...By balanced I mean the voltages between phases are close to one another...

    The "Phase Changer" is different by having seven sets of capacitors and the voltages are monitored by electronics... When different loads are applied it will vary what capacitors are switched on and off to try to keep the phase to phase voltages the same...

    With the simple single capacitor rotary units if you are running say a 2hp motor and at that the voltages between phases are say 415, 400, 410.. If you switch on a 7.5hp motor the voltages will change to maybe 415, 360, 430, this is because the single capacitors can only balance the voltage at one particular load, which when you build it you work out by putting in different value capacitors.

    While with the phase changer when you switch on the 7.5hp motor it is just like you manually switching over to a different set of valued capacitors, except the machine does it automatically via electronics, and thus the voltage is restored to a semi balanced state... No phase converter will give you 415, 415, 415 between voltages, there is always a difference...


    One phase to phase voltage will always be 415V as this is the phase that originates at the power station.

    There is another company in WA making rotary phase converters as well... I could not follow there website back when I was looking so went with the victorian company..

    The only other method to create three phase is by a static phase converter...This is a solid state electronic device that you connect to the motor...AFAIK you can only run one motor off a single solid state converter at a time.. I am not sure that these devices change the 240V incoming voltage to 415V either...Some might...

    This all seems right, but there is a mistake in the last paragraph. Let me say first up that I have no electrical training, in fact I am a rigger, although I do have an interest in things electric and electronic.
    I don't know the specific models mentioned, and can't comment on them, but the statements all sound o.k. and the last paragraph would be right if the words "static phase converter" were chamged to V.S.D. or V.F.D. (which stand for variable speed or frequency drive). As Vernonv has stated the static converter is basically a rotary converter without the idler motor. It is nowhere near as good as a rotary converter, but would be ok for a suds pump or other small loads, or even for tools like grinders which you could spin over by hand if they were reluctant to start on their own. They can usually be readily converted to a rotary phase converter by adding a suitable 3 phase idler motor.
    A VSD has some useful advantages, such as adjustable speed, acceleration and deceleration, all this with comprehensive motor protection. Although the common wisdom states that they can only run one motor at a time, I have heard that some can run a seperate motor as well, such as a suds pump as long as the primary motor was running first. I have not seen this done however.
    Again I can't give model numbers, I am fairly certain that some VSDs do incorporate a transformer or an auto-transformer to raise the 3 phase voltage from 240 to 415 volts. These models would likely cost more than the standard variety however.
    For those who are not familiar with the various modes of connecting electric motors, most 3 phase motors can be connected in delta or star, or as our american friends would say in "Y" configuration. This is done by changing the links in the connection box, or in some cases by digging into the windings to find the star point, this best being done by a rewinder. A motor wound for a 415v star configuration, when connected in delta requires a 240v supply, and as most of the 1hp and above 3 phase motors were wound star for 415v this works o.k. with the majority of VFDs.
    Let me stress again that I do not have electrical training, but if I have made any major blues hopefully someone will correct me. Hope this helps,
    Ropetangler.

  9. #69
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    Quote Originally Posted by Ropetangler View Post
    I don't know the specific models mentioned, and can't comment on them, but the statements all sound o.k. and the last paragraph would be right if the words "static phase converter" were chamged to V.S.D. or V.F.D. (which stand for variable speed or frequency drive).
    There is a new type of phase converter that sells in the US that is essentially a static phase converter, no moving parts but is not a VFD.


    Phase Converter, Digital Phase Converters - Phase Perfect

  10. #70
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    Quote Originally Posted by Ropetangler View Post
    ..., but would be ok for a suds pump or other small loads, or even for tools like grinders which you could spin over by hand if they were reluctant to start on their own.
    That is not quite true - a static phase converter can be configured to start pretty much any motor regardless of load (for the most part - certainly if a RPC can start it, an SPC can also be configured to start it).
    Cheers.

    Vernon.
    __________________________________________________
    Bite off more than you can chew and then chew like crazy.

  11. #71
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    Quote Originally Posted by .RC. View Post
    There is a new type of phase converter that sells in the US that is essentially a static phase converter, no moving parts but is not a VFD.


    Phase Converter, Digital Phase Converters - Phase Perfect
    Hi all,
    While it is true that the digital phase converter which .RC. has linked to in his post above, is a static converter in the sense that it contains no idler motor to generate the missing phase, I was using the term in the accepted vernacular way, or convention, meaning a phase converter consisting of capacitors to generate a phase shift to run a motor, without having an idler motor.
    If we take a static phase converter to be any phase converter, not having an idler, then even VFDs would have to be called static converters, which as far as I know, is not accepted convention.
    I don't have any knowledge of Phase Perfects digital phase converter, (they don't refer to it as a static converter as far as I can see) but I imagine that it might be basically a VFD type device without user changeable frequency. It may also have switchable (by electronic means) capacitors to maintain balance, or it may just adjust the phase generation to keep the currents balanced. I could imagine that this would be a minor redesign of pretty standard VFD practice. It may have advantages such as simplicity where there is no need of speed variation, and perhaps costs would be lower and the interface having fewer controls to be fiddled with and to go wrong could be advantageous to some. Regards,
    Ropetangler.

  12. #72
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    Quote Originally Posted by Vernonv View Post
    That is not quite true - a static phase converter can be configured to start pretty much any motor regardless of load (for the most part - certainly if a RPC can start it, an SPC can also be configured to start it).
    Hi again, you are right Vernonv, I gave a poor example of an RPCs advantage over a Static Converter. The main benefit of an RPC is possibly the ability to run a whole workshop of 3 phase machines, off the one machine, whereas the static converter would be less happy with changing loads, as it only has the 2 phases it generates and would not generally be as well tuned to its load as a rotary would be. I guess that if you optimised it for largish loads, and you were running a big load, any smaller loads would be getting a reasonably acceptable supply, but it would be different if you mainly ran light loads, and had the unit tuned to suit, but on occasions needed to run a heavy load, I think an RPC would do it better. That's my take on it anyway, Regards to all,
    Ropetangler.

  13. #73
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    Found this on youtube....

    Seems to be getting 400V out of a 240V supply using a motor only...

    [ame=http://www.youtube.com/watch?v=TXVlIU73yFg]YouTube - 230 Volts 1 phase to 400 Volts 3 phase rotary converter[/ame]

  14. #74
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    And a pile of capacitors.
    I thought that was how all rotary convertors worked?
    I'd like to say I understood these things but really dont. Something about using the capacitors to put the windings out of phase, 400V phase to phase, easy lol.
    The problem (as i understand it and I could be wrong) is that the size of the capacitors needed changes with load. So you need to set your capacitor size to a mid point.
    Still he does make my wiring look neat

    Stuart

  15. #75
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    Quote Originally Posted by Stustoys View Post
    I thought that was how all rotary convertors worked?
    I don't know of any that convert 240V to 415V without a transformer on the input...

    But you are right on the phase to phase bit...

    If you generate 3 separate 240V AC circuits and put them out of sync by 60 degrees with each connected via common neutral you get 415V between phases but still have 240V from phase to neutral.

    Here is a question... With the people who have built 240V phase converters, what voltage do you get from a phase to neutral? I guess it is 133V. (240 cosine 60)

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