Types of cores Flashcards
What are the 4 types of cores?
- EI
- Strip
- Wound
- Toroid
The HV winding is typically the outer winding (True/False)?
True
Is the LV winding typically the outer or inner winding?
Inner
Which of the 4 cores cannot accommodate all voltage ranges?
EI
Which of the 4 cores (multiple) can accommodate all voltage ranges?
- Toroid
- Wound
- Strip
Which of the 4 cores use a coil that is not placed on the leg of the core?
Toroid
All types of cores are created from a roll of which type of steel?
Laminated silicon
How are the windings wound?
Concentrically
The EI core is usually used on which type of transformer?
Small, single phase trx up to 5000VA
Which core is usually punched out of strip laminations?
EI core
The flux in the bottom yoke of the EI core is cross grain. What are 2 things that result in this?
Higher losses
Higher Iex
For an EI core is a lower or higher grade of steel used? What is the purpose of this?
Lower
The lamination is thicker
What type of insulation is used for an EI core?
Varnish
As a result of the design choices for insulation and steel, what is the stacking factor of EI cores?
0.9 to 0.92
When building an EI core using the Butt gap method, how are the E laminations stacked?
Stacked up, then uprighted
Where is the coil placed on an EI core?
On the center leg
What is the advantage of the butt gap method for EI cores?
Easier to stack
What is the disadvantage of the butt gap method for EI cores?
Higher Iex and core losses
What is the disadvantage of interleaving an EI core?
More time consuming
What is the advantage of interleaving an EI core?
The effective gap is reduced
What are the 3 types of strip core?
- Butt and Lap
- Scrapless Mitre
- Full Mitre
For an EI core, the coil must be designed to fit the core (True/False)?
True
For a strip core, the coil must be designed to fit the core (true/False)?
False. The core is designed to fit the coil.
Strip core laminations come in standard widths (true/false)?
True
Why must the coil be designed to fit the core for EI?
The center lam. determines all the dimensions
Why must the core be designed to fit the coil for strip?
The strip cores have more flexibility
for a butt and lap construction , where must the flux cross the grain?
At the corners
What is true about core losses, excitation VA, and noise level?
They are the highest out of the 3 types of strip core
How many gaps are in a butt and lap construction?
7
How many gaps are in a scrapless mitre construction?
8
What is true about scrapless mitre construction cross grain flux?
It is minimal
What is another name for scrapless mitre?
Partial mitre
What is true about the cross grain flux for full mitre construction?
There is no cross grain flux
How many gaps are full mitre construction?
6
Which of the 3 types of strip cores have the lowest losses, Iex, and noise level?
Full mitre
Which strip constuction has 2 45 degree cuts at the same time?
Full mitre
A toroid core is used for which type of transformer?
CTs
Do toroid cores utilize a primary winding?
No. A conductor is used as the primary. There is still a secondary
A rectangular winding is less space efficient (t/f)
False. It is more efficient.
A rectangular winding has worse short circuit capability (t/f)
True
A circular winding takes up less space (t/f)
False
Due to the circular winding taking up more space, what does that mean for the core in terms of size?
The core becomes bigger
A circular winding is easier to wind because everything is _______
Symmetrical
What is the shape of a core for a circular winding?
Square
What is the shape of a core for a rectangular winding?
Rectangular
What are the 4 types of windings?
- Scatter
- Layer
- Foil
- Disc
What is the most common winding?
Layer
What range of current is layer winding used for?
Less than 1000A
What range of voltage is layer winding used for?
Medium voltage ranges
Layer winding can be used for inner windings but not outer windings (true/False)?
False. It can be used for both
Disc winding is used as an outer winding only (t/f)?
True
Disc winding is used for when voltage is very high (t/f?
True
What are the 2 types of conductors that foil winding can be?
Copper and aluminum
