What is the correct method for counting poles in a 3-phase induction motor?

  • #1
BlackMelon
43
7
(I have modified the picture a little bit for clarity)

Hi there!

I had a chat with my colleague. He believes that the 3-phase induction motor on the picture below has 2-poles.
There are 12 slots. Each phase contain 2 coils. I have showed how the coils are connected for the phase W at the bottom.
The waveform belongs to current of each phase. For notations, when the current is entering the slot W1 (crossed symbol in the hand drawing), the same current leaves the slot W2 (dotted symbol in the hand drawing).

So from the waveform, I take a sample of current flows when wt = 0 degree, where w is angular frequency (U1 = 0, W1 = positive, V1 = negative). Using the right hand rule, I founded that there are 6 poles.

I would like to know whether me or my colleague made any mistakes?Melon.

1694708297878.jpeg
 

Attachments

  • 1694703027030.jpeg
    1694703027030.jpeg
    41.1 KB · Views: 53
Last edited:
Engineering news on Phys.org
  • #2
If you made a mistake, then it is probably observational, and we have been presented with the same data.

The ultimate test needs to be: does the unloaded motor run just below synchronous speed, or just below half twice synchronous speed.
 
Last edited:
  • #3
Aren't number of poles is usually defined per phase?
 
  • #4
Averagesupernova said:
Aren't number of poles is usually defined per phase?
Well, I understand your point. You bring the phase W like I drew and then examine its number of poles (4 poles).
However, when you input the 3 phase currents into the motor, the number of poles will not be 4x3. Rather, it will still be 4, considering the directions of all the currents in the stator.
Baluncore said:
If you made a mistake, then it is probably observational, and we have been presented with the same data.

The ultimate test needs to be: does the unloaded motor run just below synchronous speed, or just below half twice synchronous speed.
Thank you for the advice. :) :)
 
  • #5
Guys, I got the answer for the question I asked. The distribution of windings' positions are incorrect. (The way I analyzed the number of poles was correct and showed abnormality). Rather, the distribution should be done as the picture below.
According to the right and rule (The thumb is the magnetic field. The rest of the fingers are the current). Please not that 6 adjacent phase zones form 1 pole in the air gap.
For example at 30 degree electrical angle, U, -V, W and -U, V, -W form a south pole.
1695272824009.jpeg


1695271093009.jpeg

1695271170161.jpeg
 

Attachments

  • 1695271081822.jpeg
    1695271081822.jpeg
    37.6 KB · Views: 45
  • 1695271104429.jpeg
    1695271104429.jpeg
    52 KB · Views: 46
Last edited:
  • Like
Likes Baluncore

1. What is the purpose of counting poles in a 3-phase induction motor?

The number of poles in a 3-phase induction motor determines the speed at which the motor rotates. It is important to count the poles correctly to ensure the motor operates at the desired speed.

2. How do I determine the number of poles in a 3-phase induction motor?

The number of poles in a 3-phase induction motor can be determined by counting the number of pairs of poles on the stator. Each pair of poles represents one pole on the rotor.

3. What is the correct method for counting poles in a 3-phase induction motor?

The correct method for counting poles in a 3-phase induction motor is to start at one end of the stator and count the number of pairs of poles, then multiply that number by two to get the total number of poles.

4. Can the number of poles in a 3-phase induction motor be changed?

No, the number of poles in a 3-phase induction motor is fixed and cannot be changed. However, the speed of the motor can be adjusted by changing the frequency of the power supply.

5. Why is it important to count poles correctly in a 3-phase induction motor?

Counting poles correctly in a 3-phase induction motor ensures that the motor operates at the desired speed and prevents any potential damage or malfunction. It also helps in selecting the appropriate motor for a specific application.

Similar threads

Replies
2
Views
649
Replies
22
Views
3K
Replies
23
Views
3K
Replies
1
Views
13K
Replies
4
Views
2K
  • Electrical Engineering
Replies
3
Views
4K
  • Electrical Engineering
Replies
2
Views
1K
  • Electrical Engineering
Replies
17
Views
2K
Replies
3
Views
1K
  • Electrical Engineering
Replies
1
Views
2K
Back
Top