Powering a near full rated capacity single ph load from three ph source

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I did not read through all of it carefully, but aren't they doing pretty much same thing that is done when trying to derive a two phase system from a three phase supply? And they essentially describe that in the first paragraph of the introduction.

"transfers three-phase electric power to a pair of single phase feeding circuits"
 
kwired said:
I did not read through all of it carefully, but aren't they doing pretty much same thing that is done when trying to derive a two phase system from a three phase supply? And they essentially describe that in the first paragraph of the introduction.

"transfers three-phase electric power to a pair of single phase feeding circuits"
Click to expand...

See figure 2. The traditional AC electrification configuration generates two phases to power two feed lines that count on two tracks to have about the equal load to balance the loading on three phase side. This obviously doesn't work with single-line track.

So, it uses active electronics connected to both phases and spread a single phase load across both phases on the secondary of Scott xfrmer,therefore provide three phase to single phase conversion that loads the primary side evenly. It essentially does what a 3ph-to-1ph MG set does without moving parts.

It's not an issue with DC electrification as rectifier bridge can be used to provide DC from all three phases and load them evenly.

As for 3ph to 1ph, I'm seeing three ways... MG set, double conversion 3ph to DC via bridge, then DC to AC via inverter. or the aforementioned setup.


This is a huge locomotive application, but I'm wondering if it can be effectively scaled down to 10kVA to 250kVA range for example supporting large single phase load on a 3ph generator.
 
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Electric-Light said:
See figure 2. The traditional AC electrification configuration generates two phases to power two feed lines that count on two tracks to have about the equal load to balance the loading on three phase side. This obviously doesn't work with single-line track.

So, it uses active electronics connected to both phases and spread a single phase load across both phases on the secondary of Scott xfrmer,therefore provide three phase to single phase conversion that loads the primary side evenly. It essentially does what a 3ph-to-1ph MG set does without moving parts.

It's not an issue with DC electrification as rectifier bridge can be used to provide DC from all three phases and load them evenly.

As for 3ph to 1ph, I'm seeing three ways... MG set, double conversion 3ph to DC via bridge, then DC to AC via inverter. or the aforementioned setup.


This is a huge locomotive application, but I'm wondering if it can be effectively scaled down to 10kVA to 250kVA range for example supporting large single phase load on a 3ph generator.
Click to expand...

I think we are both seeing the same thing here. The Scott transformer is going to create two single phase outputs on the secondary, those outputs can not be connected in parallel because they are not in phase with one another. They can drive two phase loads or single phase loads. In the locomotive example you gave the system is balanced because each phase drives a similar load.

Could this work on a smaller scale? Yes. But transformer may not be worth the cost when you likely already have capability and capacity to drive the loads.
 
kwired said:
In the locomotive example you gave the system is balanced because each phase drives a similar load.
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The inverters + capacitor design discussed in paper is to provide ONE single phase power from Scott T transformer. A substation can't load both phases if there is only one train line. The two phase setup can only work if there are two tracks served.

Permitting one single phase output to load both sides evenly is the entire purpose of the inverters.
 
Electric-Light said:
The inverters + capacitor design discussed in paper is to provide ONE single phase power from Scott T transformer. A substation can't load both phases if there is only one train line. The two phase setup can only work if there are two tracks served.

Permitting one single phase output to load both sides evenly is the entire purpose of the inverters.
Click to expand...

I don't understand why the scott transformer is needed if you are also going to use an inverter. You should be able to just rectify the three phase input then use an inverter to derive the desired single phase??
 
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