Lecture Notes: Autotransformers in X-Ray Circuitry

Introduction

• Focus on autotransformers in x-ray circuit systems.
• Autotransformers are used when slight voltage changes are needed.
• Differ from traditional transformers as they have a single coil functioning as both primary and secondary coils.

Structure and Function

• Single Coil System: Utilizes self-induction.
  • Primary aspect acts as primary coil.
  • Secondary aspect acts as secondary coil.
• Control via Taps:
  • Taps slide to select coils included in primary and secondary aspects.
  • Number of coils determines if it functions as a step-up or step-down transformer.

Operation

• Voltage and Turns Ratio:
  • Apply transformer equations to determine turns ratio and resulting voltage.
  • Primary turns (NP): Coils in primary side taps.
  • Secondary turns (NS): Coils in secondary side taps.
• Current Supply:
  • Supplies current to high-voltage step-up transformer and filament step-down transformer.

Voltage Regulation

• Process:
  • Starts with 220 volts from a line compensator.
  • Technologist selects kVp on control panel; taps adjust voltage.
  • Example: 76 kVp selection adjusts 220 volts to 76 volts.
  • Step-up transformer converts 76 volts to 76,000 volts (adequate for x-ray image).

Amperage Control

• Functionality:
  • Controls mA based on console selections.
  • 220 volts moves through the circuit, voltage decreases, and amperage increases.
  • Current travels to step-down filament transformer for further voltage decrease and amperage increase.

Key Concepts and Takeaways

• Auto Transformer Details:
  • Incoming current: 220 volts AC.
  • Single coil with primary and secondary sides.
  • Used for small voltage adjustments; operates on self-induction.
• Output:
  • Provides specific voltage to high-voltage transformer.
  • Provides specific amperage to filament transformer.
• Transformer Law Equation:
  • Understand application and calculation of turns ratio.

Conclusion

• Importance of understanding autotransformers in x-ray circuits.
• Reminder to review transformer law equations for exams.