Phase to neutral current, final destination of current

Thread Starter

TheSpArK505

Joined Sep 25, 2013
111
Good day guys,

My head has been spinning about AC power, I will ask directly my question, refer to the attached drawing( kindergarten standards :D )

for phase a, during the positive cycle of the current and after it passes through the load, does it dissipate in the ground. like literally absorbed by soil and not coming back? or what exactly is happening ?!
 

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MaxHeadRoom

Joined Jul 18, 2013
19,057
That is the same GND referencing as used in UK etc, the neutral point of a 3 phase transformer is Earth grounded, for current to flow through a return path using GND, one of the phases would be needed to be connected to the top power rail.
Normally there is also a neutral ran from the star point to the supply, so in effect the GND would only be a reference point in this configuration.
Max.
 

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nsaspook

Joined Aug 27, 2009
6,283
Electric current must also form a complete loop back to the source whether AC or DC.
It can never just "dissipate".
Exactly, all the charge that moves in the circuit already exists in the circuit and no charge is dissipated because the charge carriers don't carry electrical energy in the circuit. Any energy in electrons (a charge carrier moving as a current) is dissipated as heat and is subtracted from the electrical energy in the circuit.
 

MaxHeadRoom

Joined Jul 18, 2013
19,057
@TheSpArK505 Actually in your drawing if the 'a' phase is connected to the 's' (source) as shown in a non-isolated condition, then the return current will flow through earth ground path as shown in the fist diag in the PDF I posted.
Your DWG is not that clear.
Max.
 

MrAl

Joined Jun 17, 2014
6,501
Hi,

Here is yet another rough analogy to current flow. I call this the "magnet and steel ball bearings" analogy.

We have a big sewer pipe above ground that forms a circular path as a torus. A small object that moves in the pipe that starts out at a point A always gets back to that point at some time later if there is a continuous clockwise movement of that object and that is because the loop is closed.
Now we partially fill the pipe with steel ball bearings so that they are distributed somewhat evenly around the entire path.
Note that none of the steel balls are moving yet they are just sitting there.

Next we take a big strong magnet and place it outside of the pipe, then move it around the outside of the pipe in a clockwise direction. Some of the balls are attracted to the magnet so they try to follow the path but still constrained to inside the pipe. After the magnet makes one complete revolution some of the ball bearings have moved clockwise but as one moves another one takes it's place.

Now imagine a set of ring shaped magnets each set a distance apart around the pipes circumference and spaced equally. The pipe fits nicely through each ring as their inside diameter is just slightly larger than the pipes diameter.
Now move all the magnets clockwise at the same time. The balls in each sector of the pipe follow their respective magnets and move clockwise. That causes them to rotate clockwise around the inside of the pipe indefinitely. As they move, the collisde with other balls, and that causes them to move in directions other than clockwise. Some might move forward while others move a little side to side, while others move backwards slightly, then change direction again when they hit something else. That random movement slows their tranvle down so they cant follow the magnets as fast as the magnets are moving, but they still move clockwise just slower.

So what caused the bearings to move? The field from the magnet, the magnetic field.
What slowed them down? The random collisions.

Ok, so that was a rough analogy where we used a magnetic field to make it more intuitive. In reality it is a combination of magnetic and electric fields, but we'll stick with magnetic only because of the intuitive value.

To improve the rough analogy, we replace each ball bearing with a group of ball bearings. Each group has it's own central spherical magnet that is fairly strong and the groups are tightly packed inside the pipe now, and the balls cluster around the central magnet and stay there clinging to it until something comes along and knocks one of them closest to the outside of the cluster off. That ball is then free to move even though the entire clusters are not free to move because they are packed tightly into the pipe.
Now when the ring magnets are rotated around the circumference of the pipe, the free balls knock into the cluster groups and knock others off and then they move and some take their place, and this repeats all around the inside of the pipe so that some of the balls make it all the way around.

Now to improve the analogy once again, we get rid of the pipe. The clusters stay together in the form that the pipe once took though because they are bound together through the fact that some clusters share balls between them, so they stay stuck together even though some are free to move when a collision occurs. The moving balls are what we call current.

Now so far we've only taken a look at what happens internally to the groups. Externally, we might see some balls on the outside edge of the groups moving from group to group even though we cant see inside the central region of the tight pack of clusters. We might see some balls moving around the outside edge of the circumference. This would make the construction look like there was something vibrating constantly on the outside surface of the torus. However, if the ball bearings were made small enough, we would not be able to see anything moving, and there is little tendency for a ball to jump out of the torus because the magnetic attraction inside is too great.

In reality this view is at room temperature and there are other forces at work and particles that are not steel balls, but most people have a grasp of what simple magnetic attraction is so this view is a little more intuitive.
 
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mvas

Joined Jun 19, 2017
538
Previously on AAC we discussed SWER - SIngle Wire Earth Return, where current in the Ground Wire is allowed
https://forum.allaboutcircuits.com/threads/the-logic-behind-earthing.157325/#post-1363197

Your title states: "Phase to Neutral Current"
But then the drawing show a 3 Phase Wye with NO Neutral and then asks about current via Ground Rods.
If there is a Neutral Wire, then by design, there is little to no current flowing through the Ground Rod.
 
Last edited:

nsaspook

Joined Aug 27, 2009
6,283
Hi,

Here is yet another rough analogy to current flow. I call this the "magnet and steel ball bearings" analogy.

We have a big sewer pipe above ground that forms a circular path as a torus. A small object that moves in the pipe that starts out at a point A always gets back to that point at some time later if there is a continuous clockwise movement of that object and that is because the loop is closed.
Now we partially fill the pipe with steel ball bearings so that they are distributed somewhat evenly around the entire path.
Note that none of the steel balls are moving yet they are just sitting there.

Next we take a big strong magnet and place it outside of the pipe, then move it around the outside of the pipe in a clockwise direction. Some of the balls are attracted to the magnet so they try to follow the path but still constrained to inside the pipe. After the magnet makes one complete revolution some of the ball bearings have moved clockwise but as one moves another one takes it's place.

Now imagine a set of ring shaped magnets each set a distance apart around the pipes circumference and spaced equally. The pipe fits nicely through each ring as their inside diameter is just slightly larger than the pipes diameter.
Now move all the magnets clockwise at the same time. The balls in each sector of the pipe follow their respective magnets and move clockwise. That causes them to rotate clockwise around the inside of the pipe indefinitely. As they move, the collisde with other balls, and that causes them to move in directions other than clockwise. Some might move forward while others move a little side to side, while others move backwards slightly, then change direction again when they hit something else. That random movement slows their tranvle down so they cant follow the magnets as fast as the magnets are moving, but they still move clockwise just slower.

So what caused the bearings to move? The field from the magnet, the magnetic field.
What slowed them down? The random collisions.

Ok, so that was a rough analogy where we used a magnetic field to make it more intuitive. In reality it is a combination of magnetic and electric fields, but we'll stick with magnetic only because of the intuitive value.

To improve the rough analogy, we replace each ball bearing with a group of ball bearings. Each group has it's own central spherical magnet that is fairly strong and the groups are tightly packed inside the pipe now, and the balls cluster around the central magnet and stay there clinging to it until something comes along and knocks one of them closest to the outside of the cluster off. That ball is then free to move even though the entire clusters are not free to move because they are packed tightly into the pipe.
Now when the ring magnets are rotated around the circumference of the pipe, the free balls knock into the cluster groups and knock others off and then they move and some take their place, and this repeats all around the inside of the pipe so that some of the balls make it all the way around.

Now to improve the analogy once again, we get rid of the pipe. The clusters stay together in the form that the pipe once took though because they are bound together through the fact that some clusters share balls between them, so they stay stuck together even though some are free to move when a collision occurs. The moving balls are what we call current.

Now so far we've only taken a look at what happens internally to the groups. Externally, we might see some balls on the outside edge of the groups moving from group to group even though we cant see inside the central region of the tight pack of clusters. We might see some balls moving around the outside edge of the circumference. This would make the construction look like there was something vibrating constantly on the outside surface of the torus. However, if the ball bearings were made small enough, we would not be able to see anything moving, and there is little tendency for a ball to jump out of the torus because the magnetic attraction inside is too great.

In reality this view is at room temperature and there are other forces at work and particles that are not steel balls, but most people have a grasp of what simple magnetic attraction is so this view is a little more intuitive.
For the same amount of mental power it takes to GROK that convoluted analogy, the 'student' could have learned the actual physics of moving charge, separating charge and the electric field potential from the results from those actions.

The simple chain analogy works so much better with physics correct mechanical properties.
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
19,057
Your title states: "Phase to Neutral Current"
But then the drawing show a 3 Phase Wye with NO Neutral and then asks about current via Ground Rods.
If there is a Neutral Wire, then by design, there is little to no current flowing through the Ground Rod.
Although the Star point IS a neutral, and in the OP's sketch the neutral current flows through earth ground.
Max.
 
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