A mindbender : you never seen this before

Thread Starter

simeonz11

Joined Apr 29, 2008
98
So I have studied 3 phase systems before at school , we got a 3 phase power supply and everything there , I understand it perfectly when it comes from the wall plugs but this is a bit "mindbending" to me .

This is a solid state version of a 3 phase AC system , as you can see this is strange . I have made an very good 3 phase pure sine solid state driver with some pretty powerful amplification . Phase A,B,C are 120 degs out of phase and have same common ground , they all use same power supply .

I basicly wish to connect this as a Y source , delta load configuration .

http://www.mhhe.com/engcs/electrical/hkd/tutorials/images/t13-3.gif

I have spent much mental energy trying to figure out how I should connect it , it is very strange to me . I have much experience @ school as I just connect the alternator leads properly for this type of connection but this seems strange to me .

It seems to me like I already have my common source point , ( ground ) , is this the right connection ? Can this even be done ? I know it can be done via a transformer Y on the primary to delta on the secondary where neutral is my ground but I wanna try with no transformer . See the pic .


 

Attachments

Last edited:

Wendy

Joined Mar 24, 2008
23,415
I don't see the problem. Eliminate the load resistors and replace them with a Y configuration and ground. What am I missing? You already have a ± power source, so ground is a true ground.
 

Thread Starter

simeonz11

Joined Apr 29, 2008
98
I don't see the problem. Eliminate the load resistors and replace them with a Y configuration and ground. What am I missing? You already have a ± power source, so ground is a true ground.
Hi Bill , thx for the reply .

What do you mean Bill ? Connect them in Y connection and remove resistors ?

My load is a delta load , it has no ground .
 

Wendy

Joined Mar 24, 2008
23,415
I guess I don't understand the question. You already show a Delta load from what I can see, diagram what you want.
 

Thread Starter

simeonz11

Joined Apr 29, 2008
98
Is this what you mean bill ?

Yes this connection is easier on the mind and would work but I will not be using Y load . Plz ignore the 30 amps , this is just for example purpose .

So my Diagram for delta load is good ?
 

Attachments

Last edited:

Wendy

Joined Mar 24, 2008
23,415
If you can call using 30A through an analog design good. :D

I'd go with MOSFETs and PWM, or at least with PWM, it would be alot more efficient on the transistor side.
 

Thread Starter

simeonz11

Joined Apr 29, 2008
98
O that was just for showing the schem , its an image I found on google , ignore all about that 30 amps I wont be using anything near that .
 

JoeJester

Joined Apr 26, 2005
4,390
ok, you want a wye generator and delta load.

do you have a three phase generator?

on the attached simulation, to get it to work, I added 0.1 ohms to the generator, otherwise the simulation would not work properly.
 

Attachments

Thread Starter

simeonz11

Joined Apr 29, 2008
98
I am producing 3 x AC sine wave using 3 x pnp/npn pairs , sine waves are out of phase by 120 degrees and use the same power supply and have the same voltage .

http://hades.mech.northwestern.edu/images/2/20/Transistor_push_pull_follower.gif

When operating each phase seperatly they all share common ground , I know they can be connected to a Y load but I wanna connect them to a delta load , this becomes confusing as I do not know what to do with the source ground , I believe it is simply not connected to anything just as my diagram in my first post , it is already connected since they all share the same ground of the power supply .
 

Wendy

Joined Mar 24, 2008
23,415
You have all the basic requirements. The ground is irrelevant, but potentially useful. If they are 120° apart then you are already there.

Just ignore the ground if you don't need it.
 

eblc1388

Joined Nov 28, 2008
1,542
When operating each phase seperatly they all share common ground , I know they can be connected to a Y load but I wanna connect them to a delta load , this becomes confusing as I do not know what to do with the source ground , I believe it is simply not connected to anything just as my diagram in my first post , it is already connected since they all share the same ground of the power supply .
In a delta connected load, you don't need the ground(common) connection as there isn't any on the load.

Think of the situation in two phase as in using a two channel audio amplifier in bridge configuration. The speaker is connected across the two outputs of each channel. The common of the amplifier output is not used.
 

williamj

Joined Sep 3, 2009
180
SIMEONZ11,

In industry, on a Delta configuration any corner connection of two windings is grounded and the center tap of any Y configuration is always grounded (as shown in the attachments). The ungrounded coil of the Delta configuration is (was) considered or labeled as the "wild leg" or phase.

On the face of it, it looks as if there is a direct short on the Y configuration to ground, and there is. But bear in mind that the earth ground actually offers quite a bit of resistance between the two points (and there is generally a large distance between the two points). Current flow always follows the path of least resistance and the path of least resistance here is through the windings of the Delta configuration there by avoiding the "short' circuit as it where. (I think) LOLOL!

Hope this helps,

williamj
 

Attachments

Top