Running the UMC from a 4 pin outlet 3 phase

[eclectricdave]

Occasionally we will come up with 3 phase power but only 4 pins L1 L2 L3 & E. The Tes neads a Neutral. This pin is virtually at ground potential. I removed the 3 pin adapter and used solar fittings to access the pins on the other end of the adapter A 4 pin plug was used to test the idea first. We used a 12kVA Diesel gen set which had a neutral in the 5 pin. Base. NB a 4 pin plug will go into a 5 pin base of same current rating. We tested first with a 50k resistor and the machine neutral. Next we removed this and connected a three phase induction motor rated at around 1 hp. This was wired in star and its neutral was connected to the adaptor neutral connection. It worked fine but we could only draw 10A per phase. We couldnt get any of the other phase pins to work on single phase except L1.when tried on single phase. You can also get N from a set of single phase transformers or a 3 phase tfrm but it is a little technical. If anyone wants more info and or pics pl contact [email protected]

 

[RichardMcN]

Interesting Dave,

So many questions ...

• So are you are saying the 3 phase motor was the successful implementation?
• What was the logic behind an induction motor as opposed to a transformer?
• What did you do with the rotor - locked? free? loaded? absent?
• Why do you think you only got 10 A when you would expect 17 A from 12 kVA gen set? The 1hp (0.75kW) motor should only take 2A or less (unless locked or no rotor).
• Etc!

 

[Chris TX]

UMC doesn't use neutral. Just make an adapter with L1, L2, and Ground/Earth. And yes, since this is a generator that will probably have a floating ground, the GFCI will give you a red light. Ground will need a resistor to one of the legs (L1). Lots of info on the web for this generator "trick". Cheers!

 

[eclectricdave]

Interesting Dave,

So many questions ...

• So are you are saying the 3 phase motor was the successful implementation?
• What was the logic behind an induction motor as opposed to a transformer?
• What did you do with the rotor - locked? free? loaded? absent?
• Why do you think you only got 10 A when you would expect 17 A from 12 kVA gen set? The 1hp (0.75kW) motor should only take 2A or less (unless locked or no rotor

If the IM worked so will a transformer set star delta. A set of three single phase or a three limb ("core") type is best. I didnt try it though.
I figure motors will be easier to get and probably cheaper. You need one with a neutral or facility to do star or delta wiring.
The motor must be rotating
The adaptor would only allow 10A. per phase. It should have done 16A per phase.
The purpose of the motor is to provide a neutral point to trick the adaptor. There should be no neutral current except possibly at startup allowing for different properties of the individual chargers at soft start.
The same could be done by connecting N to E at the adaptor except this is an illegal and dangerous connection as only one N-E connection is permitted at the switchbox box due to the needs of the RCD
To speedup charging at single phase premises with UMC you could wire up 3 extension leads for 30A charging from three different GPOs on different circuits but this is also illegal & dangerous as one or more of the male plus will be alive fed from one that is plugged in. This is another project for me to devise a safe solution. I will use contactors that have to be closed first and are then kept closed from the current flowing. Once a circuit is opened the contactor opens also avoiding live pins. There is a bit more to it than this though..

 

[eclectricdave]

UMC doesn't use neutral. Just make an adapter with L1, L2, and Ground/Earth. And yes, since this is a generator that will probably have a floating ground, the GFCI will give you a red light. Ground will need a resistor to one of the legs (L1). Lots of info on the web for this generator "trick". Cheers!

We use 415 L-L in Aus & NZ. Our UMC is different from yours. The Diesel set I mentioned was for testing only. Your scheme is for obtaining around 200V single phase from L to L with G & N connected also.