1. EET 323 – Electrical System Design Lecture 14: Transformers
Radian Belu, PhD

3. Lecture Objectives

8. A transformer consists of two or more windings coupled by mutual magnetic flux. - Primary Winding
- Secondary Winding(s)

9. Transformer Equation Faraday’s Law states that,
If the flux passes through a coil of wire, a voltage will be induced in the turns of wire. This voltage is directly proportional to the rate of change in the flux with respect of time.
If we have N turns of wire,
Lenz’s Law

13. Apparent Power Conservation E1*I1 = E2*I2

14. Transformer Equation
Where, ‘a’ is the Voltage Transformation Ratio; which will determine whether the transformer is going to be step-up or step-down
For a > 1
E1 > E2
Step-Down
For a < 1
E1 < E2
Step-Up
For a = 1
E1 = E2
Impedance
Transformer

23. Low-Voltage Transformers
LV Transformers Ratings: 600 V or less for booth primary and secondary windings
Typically Transformer Ratings: /240 V, or Y/120 V
Indoor installations and dry-type construction

36. Loading Calculations

43. Floating Υ – Δ Connections
Rule of Thumb – Lighting Transformer Leg Load:
2/3 Single-Phase Load + 1/3 3-Phase Load

52. Transformer Voltage Taps
The taps are made to high-voltage side to adjust for the variations in the supply voltage

67. Thank you for listening
THE END of the Lecture
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