"New" starting method of 3-phase motors 1

[zlatkodo]

Recently, many motors with 9 terminals have been appearing in workshops.
These motors are designed for one voltage and one speed.
For more information, please visit the following link: [URL unfurl="true"]https://winding.wixsite.com/design/post/unusual-example-from-practice[/url].
This new motor design appears to use a different starting method (hopefully will be useful for winders).
During the start, the motor is connected in a serial YD configuration, as shown in the attached diagram.
During the running period, the motor is connected in a simple 1Delta configuration.
Can someone explain this theoretical case, and how much the starting current decreases compared to other starting methods such as DOL, Y-D,or PWS?

 

[waross]

such as 1-4 and 7-10, which is incorrect.

Kirkoff may disagree with that statement.
You have neglected the current from 9-12 and the influence that it exerts on the current 1-4.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[zlatkodo]

Hi Waross,

You already possess the comprehensive diagram (in the original post) along with the simplified version (May 5, 2023 or May 11, 2023). Please attempt to compute the angle between the corresponding segments of the winding indicated by U1-U0 and U0-U2. Subsequently, kindly share the outcome with us.

Thank you.
ACW

 

[waross]

In your post of 17 May.
These two diagrams show clearly that the current through 1-4 has been shifted 30 degrees relative to the physical location.
The left hand diagram shows the angles of the currents in the respective windings.
The right hand diagram shows the physical angles, or the physical locations of the respective windings.
The currents from 9-12 and 10-7 combine to become the current through 4-1.
Comparing the left diagram with the right diagram, the current through 1-4 has shifted in phase angle but the winding has not physically changed.
When the motor is in the delta run position, the current through 1-4 will be in phase with the current through 7-10, but not when starting.
Consider a part winding motor with two identical windings, in both turns and angular location as poles.
Now feed one winding from a delta/delta transformer and feed the other winding from a delta wye transformer.

The starting connection is more complex due to the 1.73 current ratio between delta and wye, and the uneven number of coils between wye and delta, but there has to be some phase shift.

For discussion:
Remembering that starting current is highly reactive consider the effective air gaps.
As a motor load is increased, the effective air gap lengthens.
As the air gap lengthens, so also does the reactive current.
With two equal windings fed different phase angles, the rotor will take a position where the effective air gaps from each winding will be stretched 15 degrees or half of the phase angle error.
As a suggestion, the wye winding will be stronger magnetically due to more coil groups and the 1.73 wye/delta ratio.
Thus the rotor position relative to the rotating field will be closer to the wye winding.
With the relatively large effective air gap relative to the wye winding, the delta winding will have a relatively low impedance.
I suggest that the delta winding acts as a series reactor inside the wye.
Whether this is correct, I don't know, but I feel that any discussion must consider the phase shift of the current in one winding relative to the other winding and the physical locations of the windings.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[zlatkodo]

Hi Waross,
Both diagrams from May 17, 2023, represent the windings.
Regarding the diagram on the right, you already have a complete winding diagram in the original post, and it is easy to calculate the angle between the two parts of the same phase winding, marked with U1-U0 and U0-U2.
As for the diagram on the left, if you look at its source (Easa article), you will see that it depicts a standard winding with corresponding markings of 1-4 and 7-10 for the phases. Additionally, you can easily determine that both parts are in phase.
In your response, you explained the left diagram instead of calculating the angle between 1-4 and 7-10 yourself. Perhaps you can try the following approach: Draw a example of complete diagram where two parts of one phase are shifted by 30 electrical degrees.
Certainly, it can be done. Such windings exist, but they are not identical to the diagram in the original post or the diagrams discussed in the article related to the diagram on the left. These windings are known as combined YD windings, and they are not the focus of this post.
And that's why I'm not convinced that the left diagram is the best representation of the mentioned winding.
Regards
ACW

 

[waross]

And therein lies the confusion.
The motor is a delta.
When part of the delta of the delta is reconnected in star, the current shifts 30 degrees in that part of the winding.
We all know that the current in each phase of a delta winding is out of phase with the line currents.
Here's a quick experiment that you may easily do in your shop:
I don't know what the outcome may be.
Start and run a 12 lead motor as a part winding motor, connected in delta.
Measure the induced voltages in the second, open winding both phase to phase and phase to incoming line.
Put the phase to line voltages on a dual trace scope.

Now reconnect the second winding in star and start the motor on the delta winding.
Now measure the voltages of the open winding, both phase to phase and phase to incoming line.
Put the phase to line voltages on a dual trace scope.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[zlatkodo]

I'm done with it.
For those seeking to acquire new knowledge, please follow the link provided in the original post for the latest updates, accompanied by additional examples.
ACW