Reading (understanding) electric motor data? 1

[tehribo]

Hello!

I have problem in understanding electric motor data, which is given in the samples calculations of EASA's "AC Motor Redesign" book.

Please help me read it. Here are some samples. Bolded are the problem terms.

1) Data: 36 slots, 18 coils, 45 turns per coil, 1#19 wire AWG, spans for two coils/group are 1-8 and 1-10, span for one coil/group is 1-8, connected 2 and 1Y
2) Data: 36 slots and coils, 41 turns per coil, 1#22 wire AWG, span 1-8, connected 2 and 1Y


What is XXslots and XX coils?
How to understand "connected 2 and 1Y", "4 and 2 delta connection", 2 and 1 delta connection and etc.?
What is coils/group and why they are different in the first sample?

Thank you!

http://eldvigateli.com

- Electric motors Bulgaria

 

[KllrWolf]

The coil is the physical coil that you install in the motor
The span is the slots(spacing) for each side of the coil.
The coils per group is how many coils are combined together to act as one unit.

The 2 and 1Y are not something I have seen before like that. I would guess it is for dual voltage type motor saying to connect the groups in a 2 wye or 1 wye connection depending on the voltage.

 

[rhatcher]

tehribo,

1) This is a concentric winding where the number of coils is 1/2 of the number of slots.
- The stator has 36 slots and the winding has 18 coils.
- A group is the number of coils to make one pole. Group = Pole
- Coils/group means # coils per group
- Your data has some groups with 2 coils and some groups with 1 coil.
- This means a 4 pole motor (1800 rpm/60hz, 1500rpm/50hz)
- For a 4 pole motor = 6 groups of 2 coils and 6 groups of 1 coil = 4 poles per phase
- Span is the number of slots that the coils will cover. One side of the coil goes into one slot and the second side of the coil goes into another slot. For 1-8 span, one coil side is in the first slot (1) and the second coil side is placed 8 slots away.
- For a concentric motor, each coil will have a different span. In this example with two coils per group, the center coil is 1-8 span and the outside coil is 1-10 span. If the example had 4 coils per group then it could be 1-8, 1-10, 1-12, and 1-14. This is also written as 1-8,10,12,14. (concentric means 'common center' or 'same center')
- For the groups with only one coil, only one span (1-8) is needed.
- Y is the type of connection. The number 1Y or 2Y is the number of parallel circuits. For a motor with '1 and 2Y' or 1Y/2Y, then the motor is designed to operate on 2 voltages. The high voltage is connected for 1Y (1 circuit) and the low voltage is connected for 2Y (2 parallel circuits). For example 1Y = 460V and 2Y = 230V. This motor requires 6 leads and the connection for 1Y or 2Y is made externally in the terminal box.
- For IEC that you are familiar with, the nameplae will show 'Y' next to the high voltage and 'YY' next to the low voltage.

2) This motor is a lap winding where the number of coils equals the number of slots. (36 slots and 36 coils)
- If this is a 4 pole winding then there will be 3 coils per group. The total is 12 groups of 3 coils each.
- For a lap winding all of the coils have the same span. This example is 1-8.
- This winding uses a delta connection and is designed for dual voltages: '1 and 2D' or 1D/2D. The IEC nameplate would show '/\' next to the high voltage and '/\/\' next to the low voltage.


I hope that this explanation helps. Please ask any questions that you need for a better understanding.

 

[tehribo]

Thank you very much! ...again!


You made it much more clearer for me. The main problem comes from bulgarian/english translation. I mean, here we call "coil" to the "group". And "coil" we called it "section"...but this is not so important.

What isn't clear for me is..How did you understand that there are 3 coils per group?

"If this is a 4 pole winding then there will be 3 coils per group. The total is 12 groups of 3 coils each."

http://eldvigateli.com

- Electric motors Bulgaria

 

[rhatcher]

First, divide the number of coils by the number of phases (3) to determine the number of coils per phase.

Next, divide the number of coils per phase by the number of poles to determine the number of coils per pole (coils per group).

Finally, determine the order to place the groups in the stator. When all groups have the same number of coils then this is easy. When all groups do not have the same number of coils (called odd grouping) then the groups must be placed in order. The number of coils in each phase must be the same and the stator must be magnetically balanced.

(###,###,###,###...) # = number of coils per group in phase order (UVW,UVW,UVW,UVW) or (ABC,ABC,ABC,ABC). The ',' separates the poles (pole 1, pole 2, pole 3, pole 4)

1) 18 coils / 3 phases = 6 coils per phase
- 2 poles: 6 coils per phase / 2 poles = 3 coils per group. (333,333)
- 4 poles: 6 coils per phase / 4 poles = 1.5 coils per group. This requires odd grouping of 6 groups of 2 coils and 6 groups of 1 coil. (212,121,212,121)
- 6 poles: 6 coils per phase / 6 poles = 1 coil per group. (111,111,111,111,111,111)
- You cannot have more than 6 poles with 18 coils unless you use a Dahlander (consequent pole) winding.

2) 36 coils / 3 phases = 12 coils per phase
- 2 poles: 12 coils per phase / 2 poles = 6 coils per group. (666,666)
- 4 poles: 12 coils per phase / 4 poles = 3 coils per group. (333,333,333,333)
- 6 poles: 12 coils per phase / 6 poles = 2 coils per group. (222,222,222,222,222,222)
- 8 poles: 12 coils per phase / 8 poles = 1.5 coils per group. This requires odd grouping of 12 groups of 2 coils and 12 groups of 1 coil. (212,121,212,121,212,121,212,121)
- 10 poles: 12 coils per group / 10 poles = 1.2 coils per group. This requires odd grouping of 6 groups of 2 coils and 24 groups of 1 coil. (211,112,111,121,111,211,112,111,121,111)
- 12 poles: 12 coils per phase / 12 poles = 1 coil per group. (111,111,111,111,111,111,111,111,111,111,111,111)
- You cannot have more than 12 poles with 36 coils unless you use a Dahlander (consequent pole) winding.

I hope that this explanation helps your understanding.

 

[electricpete]

Great responses rhatcher. lps for you.

I have also heard the term "fractional slot winding" where you said "odd grouping"

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(2B)+(2B)' ?

 

[EngRepair]

I am following this forum for a long time and there are a lot of useful information for engineers, but I do not see the purpose of tehribo's post.
I am sure that these questions are not an engineering issue.
How to explain to someone what means "18 coils", "coils / group", " 2 and 1 delta connection " etc?
Or the purpose of this post is free advertising link.
Tehribo, I suggest you take a look at the following link for beginners:

http://www.uiitraining.com/b51a/100/15104ac_motor_rewind_intro1.htm

BTW, the your mentioned book is copyrighted material and is available only to members of the organization.

 

[tehribo]

Thank you.