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Three-Phase Transformers Lecture
Jul 2, 2024
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Three-Phase Transformers Lecture
Introduction
Sponsor:
Madox Transformer, a transformer superstore.
This lecture covers three-phase transformers, focusing on Delta primary and Y secondary configurations with a rating of 2 KVA.
Basics of Transformers
Purpose:
Converts AC voltage to another voltage without moving parts or direct wire connections between primary and secondary.
Primary Coil:
Connects across the phase and neutral.
Secondary Coil:
Completely separate, connects hot wires to ends and neutral to the center.
Output:
240V between two hot wires; 120V between neutral and hot wire (using half of the secondary coil).
Waveform:
AC sine wave observed using oscilloscope.
Single Phase vs. Three-Phase
Single-Phase for Homes:
Typically pole-mounted, connects to phase and neutral of the distribution grid.
Three-Phase for Commercial:
Provides power to commercial buildings; generated by power stations spinning magnets past coils.
Power Transmission and Distribution
Efficiency:
Increase voltage for long distances to reduce power loss; step up and step down transformers used.
Substations:
Reduce voltage at various points before distribution to homes and commercial buildings.
Transformer Construction
Coils and Cores:
Two coils of wire around a steel core; electromagnetic field induces voltage in secondary coil.
Laminated Steel Sheets:
Used to minimize energy waste (eddy currents) and heat generation.
Voltage and Turns Ratio:
Output voltage is dependent on the ratio of turns in primary and secondary coils.
Step Up/Down Transformers:
Primary to secondary turns ratio determines whether voltage is increased or decreased.
Types of Transformers
Single-Phase Transformers:
Basic construction with primary and secondary coils.
Three-Phase Transformers:
Consist of three single-phase transformers, typically for commercial applications.
Configurations:
Delta-Delta, Y-Y, Y-Delta, and Delta-Y; influences voltage and current distribution.
Practical Examples
Small Commercial Building:
Pad-mounted transformer with 12,470V Delta primary and 208/120V Y secondary, rated 150 KVA.
Large Commercial Building:
Supplies 480V 3-phase motors, 277V fluorescent lighting, and 120V outlets with a 500 KVA transformer.
Taps:
Allow adjustments for supply voltage variations to maintain the designed output voltage.
Special Configurations
Open Delta:
Uses two transformers, provides reduced capacity but cheaper to install.
High Leg Delta:
Creates a high voltage leg; dangerous for 120V appliances if improperly connected.
Calculations and Formulas
Voltage Calculations:
Use trigonometry and the square root of 3 to relate line voltage to phase voltage.
Current Calculations:
Simplified formulas for both Y and Delta configurations.
Power Conversion:
Power transferred remains the same; voltage and current are transformed.
Transformers in Practice
Commercial and Industrial Use:
Configurations for specific voltage requirements; importance of proper connection and load management.
Efficiency and Capacity:
Understanding transformer ratings, voltage, current, and safety limits.
Conclusion
Madox Transformer:
Supplier of various transformer types, supporting quick delivery and offering educational resources.
Further Learning:
References to available resources, such as mugs with formulas and diagrams, and PDF sheets for study.
Acknowledgments
Supporters:
Patreon and channel members thanked for contributions.
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