Rotary Phase Inverter

Save yourself a lot of work, weight and electricity. Go on ebay, search for phase converter. There is (or was) a guy on there selling Toshiba solid state converters. Last year I wanted to be able to run my 3 phase milling machine in the basement of my home. It's small, its quite and for $200 (1hp unit) all I had to do is hook it up and use it. But if you're determined, there is also a guy on there who for $5 will sell you all the plans for several variations of rotary schemes.

Looking back at your question I see you need a boosted voltage output. I think to do that you will have to add a transformer no matter which way you go unless maybe you use the below post route but that sounds a bit more expensive at ~$9000. For that kind of money you could probably buy a small portable generator to do 5hp.

Hello,

for £4560.00 you can buy a rotary phaze converter to run most 3 phaze machines without the need for complicated switching, I find these much better than solid state converters

Hay guys, I do this (voluntary work) for a small rural tech-school lab. your suggestion to go out and buy it, means 2 years of their budget!. Wish I could.

Can you give me the link for the plans? I could (with some efforts) get the $5.00 and scrap some parts, but not much more than this.... I have a 220V/380v transformer, and I realize that I need one. Thing is How big should this one be? is this the same power as the idler ? same power as the load? I am not an electronics engineer, and just need the converter for plasma research (physics lab), my only solution is to build one, and I don't mind it at all.

Wangito.

Well 1hp =746 watts. So you have to support 5 x 746 divided by your efficiency and I'm not sure about that but let's say 0.7 (70%). Yes the idler will eat up additional power but I really don't know how much. It was not designed to be used as a rotary transformer so I would guess you should plan on an overhead for that that is approximately 1/2 of your load but I am completely guessing. I'm surprised you couldn't find any more info than that online but maybe someone who has actually used one of these rigs will offer more advice. Good luck!

if you can send me your e-mail i will be able to send a schematic on which you could make it without much expense, we us to do it in areas without 3 phase power, phase converting s an easy task and cheap if you have a good electrician who is knolwedgeable in motor phasing

andy

nichevnh2@gmail.com

One method that I used until I moved to a place with 3 phase was to use a 3 phase 415 volt alternator driven by a 6kw 240v 50hz single phase motor. I cannot remember the exact size of the alternator but can check if you need more details. The equipment it powered was a lathe fitted with 3HP motor and a combination woodworking machine that had 3hp motors fitted. Typically the machines were used in cycles throughout the day averaging 40 to 60 minutes at a time. This method worked without any problem for about 18 months until we moved house. The motor was coupled to the alternator by 100mm dual pulleys and vee belts. Before anyone condems its inefficiency, it worked and was a lot cheaper than getting three phase installed. At the time I lived in the UK and purchased all bits from a company called Machine Mart. If I remember the whole lot cost about 500 UK pounds at the time. Hope this helps,

John

Thanks John

Every bit of information helps. I have tried to use a 3 phase motor instead of an alternator, no good. I can't spend the money for a real alternator and I HAVE the 5 HP 3phase motor... How did you excite the alternator?

Wangito.

You already have what you need. You don't even need plans. Connect the "idler" in parallel with the load with a switch (probably already on the machine). Connect the line voltage to two phases (also switched). You must have switches in order to first connect the idler before you connect the load. Apply power to the idler. It will not start on its own so you have two choices. The first one is potentially dangerous depending on how you do it. You can spin up the idler by a pull cord or use a single phase motor with a clutch to do the job. Once the idler is running it will self generate the additional phases required. Alternatively, you can attach a motor start capacitor sized for the idler motor between one of the single phase line connections and the third phase that is not connected to line. You should use a push button to only connect the capacitor until the idler is running. Once the idler is running disconnect the capacitor or disengage the starter motor and you can connect the load. This is from the plans I have, which are copyrighted so I can't send them to you but it is so simple you should be fine following this description. Let me know how it works if you try it. Remember to be safe! I don't recommend the pull cord if students are going to use it, someone might get wound up in the works!

Hi

I don't have 2 phases, as in the US distribution system (L1-L2+Neutral). The 220V We have are single phase. 2 wire only. I also need a booster transformer which I am not certain how to calculate. I have already made some plans for remote starting which is a requirement, I just don't want to invent the wheel...I understand your concern regarding copy rights. It is refreshing to know someone still respect those.

Wangito.

All you need is single phase. With only two points of connection it doesn't matter what you connect to you can only get one phase. All grid power is three phase. What is brought into your home is transformed between two of the three phases but that does not make it two-phase power. There is no such thing as two phase power with only two connections. The "ground" we have in US is only a center tap on the transformer at the pole and does not constitute a "phase". As far as your voltage is concerned if your transformer is single phase put it ahead of this rig. I assume both of your motors are of the higher voltage you want to achieve, they must be the same in this configuration. If your motor operates at the supply line voltage then you could still use it but you would then need a three phase transformer to step up the voltage to what is required for your load. This arrangement is not "ideal" in that the "generated" third phase from the idler is a bit weak due to losses but apparently it works since a lot of people have used it. I would recommend you keep an eye on the temperatures of all your components to make sure nothing is damaged. You may have to limit run time accordingly.

If you can convert to 220 single phase to 380 volts you can operate a small hp probably 5 hp with a VFD Varial Frequency Drive. This will operate on the 380 single phase after stepped up from the 220 transformer. Make sure the VFD supplier knows it is single phase input with three phase motor.

The phase converter such that are rotary will probably work, however I am not aware of the 50 hz. market. Basically all the converter consist of an induction motor with capacitors on from the powered legs to the wild leg. The wild leg does have a problem with phase angle shifts in relationship to loading and shoul not be used to operate VFD.

Basically, this was my first suggestion. However, if you read the entire thread he indicates that he has a motor to use for the idler but not the $$ to buy a cleaner solution. You are correct that the phase relationships are not perfect but it apparently works well enough to use. There should be no concern about 50 Hz since I would expect he has 50 Hz motors. The solid state converters (at least the one I used) has a selectable 50/60 Hz output. Since the only convert the line to DC they can put out any frequency and in fact you can use them that way and they compensate for motor heating at off frequencies.

Hi

I am getting smarter by the day. I also want to point out that my load although inductive, is not an electrical motor but a power transformer (power supply). I don't think that this makes any difference, but. Everything here is 50Hz , and the motor I have is a Baldor 380V/3φ/ 50/60Hz. no problem here. Reading the last paragraph of your reply, I didn't understand it. could you please explain.

Wangito.

I was responding to comment 11. I am not sure what part you don't understand but it really has more to do with a solid state phase converter and since you aren't going to use one of these it doesn't matter. Since these devices rectify the line voltage to DC and then use switching transistors to produce 3 phase AC you can vary the frequency to control the speed of the motor. I agree that the load should not matter but since you aren't getting perfect 3 phase AC from the idler you should expect some de-rating of the power supplied. It could cause additional heating or low voltage. The phase that is being generated by the motor may be a lower than normal voltage and I don't know how that might affect your device.