Thread: Single to three phase converter

Single to Three phase converter
This converter plugs into 240 volt 10 amp power point and puts out 3 phase power
It will run my Colchester lathe 7.5HP , milling machine 2HP and 3HP, bandsaw 3 HP and press 1HP
It will not run a compressor
Pickup from Healesville $1,400.00
DSCF9666.jpgDSCF9665.jpgDSCF9664.jpgDSCF9663.jpgDSCF9662.jpgDSCF9661.jpgDSCF9660.jpg

Need to include a price to conform with the rules

oops my bad

I,ts in front of the pics

Hi, I presume that you have built a Rotary Phase Converter, which will run your various machines from a 240V supply. The problem is you state that it can be done from a 10Amp supply, but 10A will barely be enough for 3 HP, assuming insignificant losses in the conversion to 3 phase. In a real world situation I would think that you would need around 30A to run a 7.5 HP motor at full load. It may well start an unloaded 7.5 HP motor, but you will not be able to run much with it with only 10A.
1 HP is near enough to 750 watts, so if you add the total HP you want to run simultaneously, and multiply by 750, you will have the total wattage. If you now divide by the supply voltage, 240 in this case, you will have the Amps required. Remember this ignores the start current, which can be 6 X the run current, especially with hard to start loads like your compressor, and it also ignores conversion losses in your system. I am not sure of the order of magnitude of the losses, but 10% at the very least I would have thought, and more likely to be 30% or even more, depending on Power factor and voltage balance between phases when under load, amongst other things.
Ray G who is active on these forums, knows far more than I do about these matters, and would gladly advise you I'm sure, and my apologies if I sound like I'm lecturing you, that is not my intention, but it is important that potential buyers are not misled by the wording of your advertisement. If the design is sound, it will run the motors as you claimed, but you will need a much bigger supply than 10 Amps to do so. Regards,
Rob.

2.5Hp Max on 10A with out overloading the cct.

If you follow this link you can see it running DSCF9687 - YouTube
100%

The purpose of the machine is to run 3phase machinery in the home work shop, which it dose.

This RPG is bordering on dangerous.
The fact that you state it runs off a 10A 240V GPO and supplies 7.5hp of 3ph power which is seververly overloading the power circuit.
There is also the lack of a safety circuit if there is mains power loss, on resumption of power the RPG motor will fail to restart overloading the windings and a good probility of a fire if you are not there to push the start caps button.
The video also show you don't start the lathe loaded ie your lathe has a clutch and you run it on a low speed @ 650RPM, show it starting @ ~2000RPM with the cluch engaged, I'm sure you will be tripping out circuit breakers.

If you are going to sell the converter make sure that it is safe.
Cheers Andy.

Originally Posted by ozheat

This RPG is bordering on dangerous.
The fact that you state it runs off a 10A 240V GPO and supplies 7.5hp of 3ph power which is seververly overloading the power circuit.
There is also the lack of a safety circuit if there is mains power loss, on resumption of power the RPG motor will fail to restart overloading the windings and a good probility of a fire if you are not there to push the start caps button.
The video also show you don't start the lathe loaded ie your lathe has a clutch and you run it on a low speed @ 650RPM, show it starting @ ~2000RPM with the cluch engaged, I'm sure you will be tripping out circuit breakers.

If you are going to sell the converter make sure that it is safe.
Cheers Andy.

Andy,
I can appreciate your concerns it is important to look at the safety aspects ofall machinery before purchasing, however most of the concerns addressed in your above post canbe alleviated by considering the following:


Firstly,when the converter is in use it dose not trip the 10 amp power supply if wewere overloading the power supply the circuit breaker would trip out.
If therewas a loss of power and it came back on the breaker would trip.
Allmachinery should be attended by a capable person at all times when running.
Also itis stated in the operating manual for this lathe that for your safety and toreduce wear and tear on the machine it should never be started with the clutchengaged.
Unfortunatelyit seems to me you are missing the point. It can cost anywhere in the range of$6,000 to $10,000 to run 3 phase power to your shed the converter enables useof several kinds of 3 phase machinery on single phase power. It does have itslimitations (It can only run the lathe at 1120rpm) but that is a 7.5hp 3 phasemotor.
What I’moffering is a chance for people like me, who enjoy using 3 phase machinery inthe shed, a low cost option to convert their power supply, something I wish Ihad 10yrs ago.

Your the one missing the point...

You claim that the converter will run a 7.5hp lathe off a 10A gpo which is wrong. 10A 240V GPO is rated at 2400W, a 7.5hp 240V @ 23.3A is ~5600W. Now tell me if that is overloading the 10A GPO powerpoint?

I don't think anyone would have questioned you if it was not the claim of 7.5hp off a 10A gpo.
As you have said the with the lathe any speed above 1120rpm trips the circuit breaker which says to me that the converter will not really run a 7.5hp motor when it has a real load on it especially as your clutch on the lathe is disengaged at startup. The circuit breaker probally trips when you apply ~3hp load on the lathe.

I'm all for RPCs, I have built a few including a 10hp @440v for a DSG lathe with a 2 speed motor which was supplied with 240v@40A wiring and if there was a power outage the converter would not try to restart because it contained safety controls. Depending on a person to switch off the converter after the power went out is irresponsible, what if it was at night and their main concern was to get out of the workshop without bumping in to dangerous machinery & equiptment in the dark? It would be easy to forget that the converter was trying to start up when the power resumes as the only indication you would have is the hum of the pony motor with its single coil energised and the run caps trying to dump high energy to the other 2 coils, even 30 secs is enough time for the coil to heat up enough to start a fire or else the run caps can explode.

I highly recommend that you drop the claim that it will run the 7.5hp lathe of a 10A GPO and to make the converter safe before trying to sell to the public, you may know its limitations but someone that you sell it too may not or not pay heed to its limitations causing damage to life or property.

Originally Posted by Allan&glen

Andy,
I can appreciate your concerns it is important to look at the safety aspects ofall machinery before purchasing, however most of the concerns addressed in your above post canbe alleviated by considering the following:


Firstly,when the converter is in use it dose not trip the 10 amp power supply if wewere overloading the power supply the circuit breaker would trip out.
If therewas a loss of power and it came back on the breaker would trip.
Allmachinery should be attended by a capable person at all times when running.
Also itis stated in the operating manual for this lathe that for your safety and toreduce wear and tear on the machine it should never be started with the clutchengaged.
Unfortunatelyit seems to me you are missing the point. It can cost anywhere in the range of$6,000 to $10,000 to run 3 phase power to your shed the converter enables useof several kinds of 3 phase machinery on single phase power. It does have itslimitations (It can only run the lathe at 1120rpm) but that is a 7.5hp 3 phasemotor.
What I’moffering is a chance for people like me, who enjoy using 3 phase machinery inthe shed, a low cost option to convert their power supply, something I wish Ihad 10yrs ago.

Please withdraw add