Types of cores

Question 1

What are the 4 types of cores?

Answer 1

1. EI
2. Strip
3. Wound
4. Toroid

Question 2

The HV winding is typically the outer winding (True/False)?

Answer 2

True

Question 3

Is the LV winding typically the outer or inner winding?

Answer 3

Inner

Question 4

Which of the 4 cores cannot accommodate all voltage ranges?

Answer 4

EI

Question 5

Which of the 4 cores (multiple) can accommodate all voltage ranges?

Answer 5

1. Toroid
2. Wound
3. Strip

Question 6

Which of the 4 cores use a coil that is not placed on the leg of the core?

Answer 6

Toroid

Question 7

All types of cores are created from a roll of which type of steel?

Answer 7

Laminated silicon

Question 8

How are the windings wound?

Answer 8

Concentrically

Question 9

The EI core is usually used on which type of transformer?

Answer 9

Small, single phase trx up to 5000VA

Question 10

Which core is usually punched out of strip laminations?

Answer 10

EI core

Question 11

The flux in the bottom yoke of the EI core is cross grain. What are 2 things that result in this?

Answer 11

Higher losses
Higher Iex

Question 12

For an EI core is a lower or higher grade of steel used? What is the purpose of this?

Answer 12

Lower
The lamination is thicker

Question 13

What type of insulation is used for an EI core?

Answer 13

Varnish

Question 14

As a result of the design choices for insulation and steel, what is the stacking factor of EI cores?

Answer 14

0.9 to 0.92

Question 15

When building an EI core using the Butt gap method, how are the E laminations stacked?

Answer 15

Stacked up, then uprighted

Question 16

Where is the coil placed on an EI core?

Answer 16

On the center leg

Question 17

What is the advantage of the butt gap method for EI cores?

Answer 17

Easier to stack

Question 18

What is the disadvantage of the butt gap method for EI cores?

Answer 18

Higher Iex and core losses

Question 19

What is the disadvantage of interleaving an EI core?

Answer 19

More time consuming

Question 20

What is the advantage of interleaving an EI core?

Answer 20

The effective gap is reduced

Question 21

What are the 3 types of strip core?

Answer 21

1. Butt and Lap
2. Scrapless Mitre
3. Full Mitre

Question 22

For an EI core, the coil must be designed to fit the core (True/False)?

Answer 22

True

Question 23

For a strip core, the coil must be designed to fit the core (true/False)?

Answer 23

False. The core is designed to fit the coil.

Question 24

Strip core laminations come in standard widths (true/false)?

Answer 24

True

Question 25

Why must the coil be designed to fit the core for EI?

Answer 25

The center lam. determines all the dimensions

Question 26

Why must the core be designed to fit the coil for strip?

Answer 26

The strip cores have more flexibility

Question 27

for a butt and lap construction , where must the flux cross the grain?

Answer 27

At the corners

Question 28

What is true about core losses, excitation VA, and noise level?

Answer 28

They are the highest out of the 3 types of strip core

Question 29

How many gaps are in a butt and lap construction?

Answer 29

7

Question 30

How many gaps are in a scrapless mitre construction?

Answer 30

8

Question 31

What is true about scrapless mitre construction cross grain flux?

Answer 31

It is minimal

Question 32

What is another name for scrapless mitre?

Answer 32

Partial mitre

Question 33

What is true about the cross grain flux for full mitre construction?

Answer 33

There is no cross grain flux

Question 34

How many gaps are full mitre construction?

Answer 34

6

Question 35

Which of the 3 types of strip cores have the lowest losses, Iex, and noise level?

Answer 35

Full mitre

Question 36

Which strip constuction has 2 45 degree cuts at the same time?

Answer 36

Full mitre

Question 37

A toroid core is used for which type of transformer?

Answer 37

CTs

Question 38

Do toroid cores utilize a primary winding?

Answer 38

No. A conductor is used as the primary. There is still a secondary

Question 39

A rectangular winding is less space efficient (t/f)

Answer 39

False. It is more efficient.

Question 40

A rectangular winding has worse short circuit capability (t/f)

Answer 40

True

Question 41

A circular winding takes up less space (t/f)

Answer 41

False

Question 42

Due to the circular winding taking up more space, what does that mean for the core in terms of size?

Answer 42

The core becomes bigger

Question 43

A circular winding is easier to wind because everything is _______

Answer 43

Symmetrical

Question 44

What is the shape of a core for a circular winding?

Answer 44

Square

Question 45

What is the shape of a core for a rectangular winding?

Answer 45

Rectangular

Question 46

What are the 4 types of windings?

Answer 46

1. Scatter 2. Layer 3. Foil 4. Disc

Question 47

What is the most common winding?

Answer 47

Layer

Question 48

What range of current is layer winding used for?

Answer 48

Less than 1000A

Question 49

What range of voltage is layer winding used for?

Answer 49

Medium voltage ranges

Question 50

Layer winding can be used for inner windings but not outer windings (true/False)?

Answer 50

False. It can be used for both

Question 51

Disc winding is used as an outer winding only (t/f)?

Answer 51

True

Question 52

Disc winding is used for when voltage is very high (t/f?

Answer 52

True

Question 53

What are the 2 types of conductors that foil winding can be?

Answer 53

Copper and aluminum