[How do I?] My 2017 Rotary Phase Converter Build

[Eddyde]

Hi markba633csi,

Thanks for your response, I see you like BMW coupes

My third paragraph is talking about how the RPC works within the YouTube video that I posted where the design gives 2 ghost legs when the Idle motor is running and only uses the Neutral within the circuit upon startup. This setup keeps the Neutral where it should be at the Star point, in the USA you do not need to use this method mainly because you already have your Live split into 2 at the consumer board within a domestic supply. These 2 Lives spin the motor without needing to use the Neutral (albeit they are both under powered compared to a real 3 phase supply)

To clarify something: The "legs" L1, L2 we get here in the states are technically not "phases"(though they are usually referred to as), they are a single phase split into 2 "legs". Thats why it's called "single phase even though there are 2 "hot legs". So here at the utility pole a single 240V phase (just like you have) is split into the two 120V legs, 180 degrees apart. When one leg is at +120V the other is at -120V acting as the return path thus the potential between the two is 240V. A 240V to neutral will give the same potential. So a single phase 240V motor will work either with 2 120V legs attached or a 240V phase and a neutral, to the motor it's the same. The phase is split here because we use 120V for lighting and small appliances. Europe et, al. don't use 120V so no need to split it.

 

[mksj]

There are available plans to for established RPC designs specific the UK/Australia electrical grids for single phase 240 to 3 phase, you can even purchase some used converters of this design :

Pardon our interruption...

TRANSWAVE Rotary Converter RT4 4kW .5.5hp - Single to 3-phase 240v to 415v | eBay

TRANSWAVE Rotary Converter RT4 4kW .5.5hp - Single to 3-phase 240v to 415v . Very good condition, cash on collection,Collection only. <br>

www.ebay.co.uk

What I do not see defined is the equipment and voltages you need and if the motors can be wired for any other voltages assuming the default is 415VAC (dual voltage). The easiest solution would be a single phase input VFD to 3 phase for 240VAC, if you need to step up the voltage to 415VAC then use a step-up transformer, then run that into a VFD. There are Chinese suppliers that have 240 to 415VAC 3 phase VFDs, there is also a UK supplier that sells similar VFDs, but expensive.

Items for sale by drives_direct_nottingham | eBay

Shop eBay for great deals from drives_direct_nottingham!

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Independent of whatever RPC/conversion methode you decide to use, a 7.5Hp compressor startup load is going to be a real challenge on a 40 Amp 240VAC single phase power source by any approach you take. The RPC consumes energy and also the output with 2 generated legs has to have significant inefficiencies with regard to power loss. Even in a ideal situation using VFD with a soft start, say a 10Hp Huanyang "single phase" input VFD, the reports I have read in the US is that the VFD usually doesn't survive very long running these types of compressors.

 

[Datum1M]

To clarify something: The "legs" L1, L2 we get here in the states are technically not "phases"(though they are usually referred to as), they are a single phase split into 2 "legs". Thats why it's called "single phase even though there are 2 "hot legs". So here at the utility pole a single 240V phase (just like you have) is split into the two 120V legs, 180 degrees apart. When one leg is at +120V the other is at -120V acting as the return path thus the potential between the two is 240V. A 240V to neutral will give the same potential. So a single phase 240V motor will work either with 2 120V legs attached or a 240V phase and a neutral, to the motor it's the same. The phase is split here because we use 120V for lighting and small appliances. Europe et, al. don't use 120V so no need to split it.

Thanks, I understand what you are saying and because they are split and attached to the 3 phase motor at L1 & L2 (120 degrees apart) this gets the motor spinning with the aid of start capacitors, so no Neutral required within the circuit. Just a side note in the UK all building sides use 110V power because in the UK they feel this is safer.

 

[Datum1M]

There are available plans to for established RPC designs specific the UK/Australia electrical grids for single phase 240 to 3 phase, you can even purchase some used converters of this design :

Pardon our interruption...

TRANSWAVE Rotary Converter RT4 4kW .5.5hp - Single to 3-phase 240v to 415v | eBay

TRANSWAVE Rotary Converter RT4 4kW .5.5hp - Single to 3-phase 240v to 415v . Very good condition, cash on collection,Collection only. <br>

www.ebay.co.uk

What I do not see defined is the equipment and voltages you need and if the motors can be wired for any other voltages assuming the default is 415VAC (dual voltage). The easiest solution would be a single phase input VFD to 3 phase for 240VAC, if you need to step up the voltage to 415VAC then use a step-up transformer, then run that into a VFD. There are Chinese suppliers that have 240 to 415VAC 3 phase VFDs, there is also a UK supplier that sells similar VFDs, but expensive.

Items for sale by drives_direct_nottingham | eBay

Shop eBay for great deals from drives_direct_nottingham!

www.ebay.co.uk

Independent of whatever RPC/conversion methode you decide to use, a 7.5Hp compressor startup load is going to be a real challenge on a 40 Amp 240VAC single phase power source by any approach you take. The RPC consumes energy and also the output with 2 generated legs has to have significant inefficiencies with regard to power loss. Even in a ideal situation using VFD with a soft start, say a 10Hp Huanyang "single phase" input VFD, the reports I have read in the US is that the VFD usually doesn't survive very long running these types of compressors.

This is a 8KW for sale secondhand for $2400 (they are $6500 new) but I was a day late and it is already sold, it runs from a 40 AMP's supply and should have started my air compressor, you can see that even secondhand they are still expensive in Australia.

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[Datum1M]

There are available plans to for established RPC designs specific the UK/Australia electrical grids for single phase 240 to 3 phase, you can even purchase some used converters of this design :

Pardon our interruption...

TRANSWAVE Rotary Converter RT4 4kW .5.5hp - Single to 3-phase 240v to 415v | eBay

TRANSWAVE Rotary Converter RT4 4kW .5.5hp - Single to 3-phase 240v to 415v . Very good condition, cash on collection,Collection only. <br>

www.ebay.co.uk

What I do not see defined is the equipment and voltages you need and if the motors can be wired for any other voltages assuming the default is 415VAC (dual voltage). The easiest solution would be a single phase input VFD to 3 phase for 240VAC, if you need to step up the voltage to 415VAC then use a step-up transformer, then run that into a VFD. There are Chinese suppliers that have 240 to 415VAC 3 phase VFDs, there is also a UK supplier that sells similar VFDs, but expensive.

Items for sale by drives_direct_nottingham | eBay

Shop eBay for great deals from drives_direct_nottingham!

www.ebay.co.uk

Independent of whatever RPC/conversion methode you decide to use, a 7.5Hp compressor startup load is going to be a real challenge on a 40 Amp 240VAC single phase power source by any approach you take. The RPC consumes energy and also the output with 2 generated legs has to have significant inefficiencies with regard to power loss. Even in a ideal situation using VFD with a soft start, say a 10Hp Huanyang "single phase" input VFD, the reports I have read in the US is that the VFD usually doesn't survive very long running these types of compressors.

I am also looking at this one which I think is a static, 5.5KV which I could add an idle motor to and turn it into a RPC, but at $1850 is it worthwhile doing so.

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[Eddyde]

I am also looking at this one which I think is a static, 5.5KV which I could add an idle motor to and turn it into a RPC, but at $1850 is it worthwhile doing so.

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A static phase converter is essentially bunch of capacitors.

Basically its a RPC without the load motor attached. it will run the motor at approx. ⅔ rated hp. Hook the motor you want to drive into the circuit and it will deliver nearly full horsepower. Note: the single phase input can be split phase or 240V phase to neutral. However, this is for a 240V motor if you need to drive a 415V motor you will need a boost transformer.

 

[Datum1M]

A static phase converter is essentially bunch of capacitors.
View attachment 310089
Basically its a RPC without the load motor attached. it will run the motor at approx. ⅔ rated hp. Hook the motor you want to drive into the circuit and it will deliver nearly full horsepower. Note: the single phase input can be split phase or 240V phase to neutral. However, this is for a 240V motor if you need to drive a 415V motor you will need a boost transformer.

Did you mean Idle motor attached rather than load motor?

I think it will be wired with the Neutral within the circuit, so I will still have the problem of the floating Neutral and $1850 makes it expensive to turn into a RPC.

 

[Eddyde]

Thanks, I understand what you are saying and because they are split and attached to the 3 phase motor at L1 & L2 (120 degrees apart) this gets the motor spinning with the aid of start capacitors, so no Neutral required within the circuit. Just a side note in the UK all building sides use 110V power because in the UK they feel this is safer.

Yes I am aware of the British construction power, I believe it is split 2 @ 55V, no neutral. The theory is a shock will likely be between one leg and ground thus only 55V and less likely to be lethal.

 

[Datum1M]

Yes I am aware of the British construction power, I believe it is split 2 @ 55V, no neutral. The theory is a shock will likely be between one leg and ground thus only 55V and less likely to be lethal.

I believe they just use a 240V to 110V step down transformer and the Neutral remains in the circuit. L1 (110V) N & E

 

[Eddyde]

Did you mean Idle motor attached rather than load motor?

I think it will be wired with the Neutral within the circuit, so I will still have the problem of the floating Neutral and $1850 makes it expensive to turn into a RPC.

A three phase 240V motor will start and run with your one phase and a neutral with a capacitors in parallel to the other phases "static converter" an additional start capacitor or pony motor will get it spinning. Hooking another motor in parallel will create a load on first motor which will then "generate" power in the 3rd "ghost" leg. However the generated power is drawn from the supplied power through induction, thus the output can never exceed the input, in fact it will be a little less as there will be heat and other losses. EDIT I was a bit fuzzy yesterday evening, I realize the above is not worded well. What I meant to say is: the power drawn from the third, ghost, leg will draw a proportional amount of power from the mains.