415 Volt D.I.Y. Phase Converter Idea's For Australia
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  1. #1
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    Default 415 Volt D.I.Y. Phase Converter Idea's For Australia

    I am posting this to give encouragement to those who are not sure if they could safely build, or how and where to get started on their own phase converter. I ask others who have built their own 415v converter, how did they do it.
    I say Australia only because I know the secondhand market reasonably well.
    I have built myself several phase converters of the Rotary and High Voltage Transformer types. I think the rotary type 415v is the better choice if it is for operating different motors, or machines with more than one 3phase motor, and if the machine has a 415v control circuit there is no further consideration, just plug it in.
    If a converter is required that outputs 415v and inputs 240v, a transformer is needed.If you wanted to use a dry isolation (double wound)type secondhand (used) say 5kVA it would probably cost you more that $1000 if you could find one, then you would still need good advice for the Neutral Bonding arrangements for the secondary side of the transformer.
    What I do, is to use old choke welding machines, because they are available and cheap on Ebay. The welder with least amount of work is something with input voltages (primary side of transformer)of 240v and 415v and then by simply re-arranging the links (jumpers) this primary winding becomes an Autotransformer which will input 240v and output 415v single phase.
    Now this welder maybe advertised as being 3phase so check the affixed manufacturers specification plate and it will usually say Single Phase. In Australia a 3phase choke welder would be a rare thing and a very big industrial thing with multiple chokes usually associated in industry like ship yards. If the power supply cable is using two conductors and an Earth whether the two conductors are a Neutral and Active or both are Actives, that means Single Phase. A lot of people think if you plug into a 3phase socket outlet that the machine must require 3phase.
    So now we have 415v single phase if it is connected to two of the terminals of a suitable 415v 3phase Idler motor and have a way of starting this Idler motor,(pony motor, button start with capacitors, button start voltage relay with capacitors, button start current relay with capacitors, rope around the shaft) we now have a working converter but you will probably want to do some balancing of the phases with the addition of run capacitors.
    By using a welder as a Autotransformer some of the advantages are, very cheap if not free, they are very available, they have their own metal enclosure.
    I would like to hear about other peoples success stories, maybe not quite there yet, maybe thinking would this thing safely work.

    Jim

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    I'm confused about the term "choke welding machine".

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    Near as I can tell, it means a transformer-based machine (not inverter). At least that seems to make some sense.

    I'm waiting for the true explanation also !

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    Hi CalG,
    A choke welder has a moving iron, or one of the Coils slides on an Iron limb.
    Like I said, in Australia they are nealy all single phase. But 415v single phase supply comfortably produces 400 or 500 Amps or more.
    It sounds like in the U.S. you achieve this with 3 phase. Would 208v be correct.

    Jim

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    Hi JST,
    All I am trying to pass on is using a welder transformer to step up our single phase voltage (240v) to the motor voltage 415v and then powering a standard 3 phase 415v motor so then we have a R.P.C. to run other 415v machines or motors.

    You have got me wondering what explanation you are waiting for.

    Jim

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    Hi jim
    Are you available for a chat?

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    Hi Laurence
    Yes I'm available.

    Jim

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    I live in Australia and need some advice on building a rpc for my 3 phase lathe

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    Canít seem to find a suitable welder to use as a transformer,found a transarc 300 but it doesnít seem to have a 240v connection

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    Hi Laurence,
    What is the power of your 3 phase Lathe motor. If you find a welder you think may be suitable, send me a picture of it's rating plate, also what area are you in because distance needs to be factored in.

    Jim

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    Quote Originally Posted by Laurence Parker View Post
    Can’t seem to find a suitable welder to use as a transformer,found a transarc 300 but it doesn’t seem to have a 240v connection
    If all else fails, strip off the welding winding and add a new winding for the 240v side - this will also give you isolation between 240 and 415, so despite the hassle a Good Thing. I did the opposite, 9 kva welder running from 240, wound a new coil for 415.

    First, you'd need to find the volts per turn of the existing windings - run five turns or so of *insulated* wire on the core, around the welding winding, measure the AC voltage on its ends and divide by number of turns, then work out how many you need for 240v, probably 150 - 200 turns but measure it and do the Hard Sums! My 415 volt coil needed 240 turns and I also added a 5v and a 10 v coil in case it needed adjustment up or down.

    I 3D printed a new coil bobbin/former to the same dimensions as the core laminations, "delaminated" the core and removed the welding winding, wound the new coil in 3mm (diameter, not CSA!) enamelled copper using a rotary table, clamps and a pistol drill (cheap turns counter from Chinese gent on EvilBay so I wouldn't lose track, under a fiver), ran the copper through a W in bearings to straighten it out - worked OK, then potted it in epoxy by bagging it and attaching vacuum pump - a bit messy but worked. Reassembled, back in the oil tank, worked fine until t he UK weather got to it and filled the tank with rain... Got around that, though!

    coil-windingf.jpg20190407_174726.jpg

    Dave H. (the other one)

    Edit: I was quoted £1500 for a transformer the spec' I needed, so even if I'd had to buy the 6" rotary table etc. to wind the coil (and the 3D printer!) I'd be quids in - the welder cost me £20 and a bad back for a week (twice), enamelled copper about £70, half a £10 roll for the 3D printer, a couple of hours each modelling the coil bobbin, winding/potting it and dismantling / assembling the transformer.

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    How good ! I’m just getting into this as a hobby and I have been seeing soo many nice 3 phase lathes but haven’t taken the plunge for fear of not being able to power it (I rent )
    I’m going to try build one of these , thanks �� perfect timing

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    Quote Originally Posted by Ads View Post
    How good ! I’m just getting into this as a hobby and I have been seeing soo many nice 3 phase lathes but haven’t taken the plunge for fear of not being able to power it (I rent )
    I’m going to try build one of these , thanks �� perfect timing
    Once you have the converter it's not just lathes, there are mills, TIG welders, grinders bench and surface - the world's your slimy shellfish

    Dave H. (the other one)

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    Default Need help

    I have a 240v small ish mill but I am excited at the prospect of more machines
    What I need to know is who has built one in aus and can give me some guidance please ? I have a reasonable grasp of whatís needed except for capacitor sizing and what can be supported on a normal 10amp circuit as found in a standard house ?
    Cheers
    Oh and I spotted a welder but it has 5 pin 3phase plug and no mention of single phase or 240v any ideas on suitability ? And what effect does a larger welder have on the setup ?

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    Hi Ads,
    The sizing of capacitors will not be a big issue. With only a 10 Amp circuit, must be smallish motors, although I think your circuit would be either 16 Amp or 20 Amp circuit breaker. It's no good looking at the plug on a welder, you need to get information from it's rating plate. I am not sure what you mean when you ask about a larger welder.

    Jim

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    a 10A 240v circuit isn't going to power much - you's be limited to about a 3HP idler, so probably 2HP usable for the biggest 3-phase machine. Is there no way to add a bigger breaker etc. for workshop use?

    I too am in a rental, asked the landlady nicely whether "a mate who's an industrial electrician" could add some circuits and now have a nice shiny metal distribution box teed into the meter tails, bunch of 16 and 32A sockets, hardwire to an isolator from a 40A breaker for the RPC, lots of 13A sockets on a ringmain... Guess who the "mate" is! Check with your landlord/landlady, although in Oz you have to have a licenced electrician do ANY work, I believe?

    Re the welders - if it's a transformer welder (i.e. not one you could lift without mates / mechanical aids) there will probably only be 3 wires in the 5-pin, for 2 of the 3 phases and the protective earth, so it can run from the 415v between phases.
    A larger welder will have a higher idling current when you're not drawing power, my 9 kva which I haven't fitted power-factor correcting capacitors to yet pulls about 8A reactive without the RPC motor running, the RPC balance caps actually reduce that once it's spinning the motor!
    The big worry with a big transformer is the initial surge on switch-on, on mine it spikes up to about 60A for a fraction of a second, so I have a "type D" time-delay breaker feeding it AND some relay logic to prevent connecting the load until the motor's spinning and prevent spinning up the motor until the transformer's powered - to separate the initial inrush currents in time.

    If you can't get 3-phase any other way, there's always generators (but neighbours might get a bit toey...)

    Dave H. (the other one)

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    Hi Jim
    I read a post from you saying a larger welder for larger motors , I canít remember where I saw it but what I mean is say a 300amp welder as opposed to the transarc tradesman one ? Probably no difference for my purpose .
    Dave I havenít looked in the fuse box but the garage is on the same circuit as almost all of the house I donít know why they did it that way but probably the same guy that poured the slanted garage floor (substantial slant !)
    Iíll check tonight , the lathe i want is an old Nuttal
    That has a 5 hp 10amp motor .
    The welder I spotted was a transarc contractor

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    Hi Ads,
    Generally welders that operate from both 240V and 415V only go as large as about 300A output, then their primary winding is only for 415V input.
    In you case as a hobby I think the transarc contractor would suit you fine. I think it has 3 input voltage options 240V, 415V, 480V as long as you are not paying to much. If you were living around Sydney or Melbourne I would think around $60 within a few weeks. But before buying make sure it's rating plate says 240V and 415V and don't be confused if it has a 3 phase plug attached. I will add that being hobby you would never be able to work that 5HP motor anywhere near full amps.
    About the Nuttal (good choice) is it cone head or gear head? but either way it will have a clutch.
    I would suggest caution before anyone changes a circuit breaker with a higher current capacity. The job of the C/B is to protect the installation.

    Jim

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    It's worth mapping out exactly what is on which circuit. It's unlikely that the garage is on the same circuit as 'almost all of the house' - but it might be on the same RCD.

    Even if you are using nothing else on the circuit, a 16-20A supply is still rather limiting. You won't be able to run a 5HP motor at continuous full power even with a VFD, let alone an RPC. Maximum welder size is likely around 200A peak, 120A continuous. Fine for most work.

    A new 32A circuit would be a really good idea.

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    Iím not sure what it is , I havenít seen it close up yet because I have no way to power it ... yet
    Would a VFD be a better choice ?
    I will continue looking for something around $50
    I think I will have access to a 4kw 3 phase motor to use as well


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