This document discusses different types of electrical materials including conducting, magnetic, and insulating materials. It focuses on copper and aluminum as highly conducting materials. Copper has the highest conductivity but is more expensive than aluminum. While aluminum has lower conductivity than copper, it has a higher cross-sectional area for the same resistance due to its lower cost and abundance. Aluminum is increasingly being used instead of copper in electrical applications due to its lower cost, although copper remains more commonly used for applications requiring high conductivity like motor windings.

1. Electrical Materials
1. Conducting Material.
2. Magnetic Material
3. Insulating Material
• Electrically Conducting Material :- This materials carry current in an
electrical machine.
• Highly Conducting Material :- Copper, Aluminum, Gold, Silver.
• Highly resistive material:- Alloys (heating elements)
Now, R=Ro(1+αΔT)
Where α= temperature coefficient of resistance
ΔT= Change in temperature of per degree Celsius
R & Ro = Initial and final value of resistance

2. Properties of Highly Conducting material
• Highest Possible Conductivity
• Less temperature Coefficient of Resistance
• Adequate Mechanical Strength and absence of brittleness
• Rollability and Draw ability.
• Good weldability and solder ability to ensure the low resistance of
joints.
• Adequate resistance to corrosion.

3. Copper
• Machine Windings
Ϭau>Ϭag>Ϭcu>Ϭal
(Gold)> (Silver)> (Copper) >(Aluminum)
Ϭ= Conductivity of the material
• It is used to construct winding of an electrical machine because the cost is
not very high and it is highly conducting.
• Copper is resistance to oxidation and corrosion.
• Hard drawn copper wires are used in electrical machine because their
mechanical strength is high
αcu =0.00393 per degree Celsius
(high)

4. Aluminum
• Since copper is getting depleted aluminum is the next best choice for
conducting material it is abundantly available
• Aluminum cannot be drawn into thin wires but it can be used to form
thin sheets.

5. Parameter Copper (Cu) Aluminum (Al)
Cost 1 0.49
Cross Section Area 1 1.62
Diameter 1 1.27
Volume 1 2.04
Weight 1 0.49
Strength 1 0.64
Comparison of Aluminum(Al) and Copper(Cu)

6. Why cross sectional area of Aluminum(Al) is higher
then the cross sectional area of the copper(Cu) ?
• As we know that
• Ϭcu > Ϭal
• So, R=∫*l/A = l/Ϭ*A
• Since, Rcu = Ral
• Now, l/Ϭcu*Acu = l/Ϭal*Aal
• Therefore Aal = Ϭcu*Acu/Ϭal > Acu
Where∫ = resistivity of the material and Ϭ = conductivity of the material
and l=length of the material and A= cross sectional area of the material
Hence cross sectional area of Aluminum is higher then the cross sectional
area of Copper.

7. • For Al wire the size of slot required is higher as compared to Copper.
• For Induction motor above 100KW output Aluminum can be used for cage
rotor.
• Aluminum can be used to form foil type low voltage winding in a
transformer.
• Aluminum can be used to construct tank of a transformer to reduce stray
losses.
• Aluminum easily gets oxidized to form Al2O3 which prevent further
oxidation.