Overview
Today's lecture covered the key parts of the x-ray circuit, their functions, locations, and the importance of understanding the flow from power supply to x-ray tube.
X-ray Circuit Basics
- The x-ray circuit powers the x-ray tube and operates using alternating current (AC) at about 220 volts.
- Main power switch, fuses, and circuit breakers protect the circuit and are located on the primary (input) side.
- A line voltage meter compensates for fluctuations to keep voltage stable at 220V.
Transformers in the Circuit
- The auto transformer is the first transformer encountered; it selects kilovoltage (kV), not produces it, and works by self-induction.
- The mA selector (also called a rheostat or variable resistor) sets the tube current and controls filament heating.
- The step up transformer increases voltage from volts to kilovolts for the x-ray tube and works by mutual induction with primary and secondary windings.
- The step down transformer (filament transformer) decreases voltage and increases current for the filament; also works by mutual induction.
Current Conversion & Rectification
- Rectifiers convert AC to direct current (DC) for the x-ray tube; usually four solid-state diodes arranged in a diamond shape.
- Rectification can be half-wave (less efficient, more gaps) or full-wave (more efficient, less voltage drop).
Voltage Ripple and Power Types
- Single phase power has 100% voltage ripple (undesirable).
- Three phase 6-pulse reduces ripple to 14%; three phase 12-pulse reduces it to 4%.
- High frequency equipment has 1% or less voltage ripple, providing more consistent power to the x-ray tube.
Circuit Diagram Tips
- Circuit diagrams may vary in appearance, but component locations and functions remain consistent.
- Know how to identify each part and its side (primary, secondary, or filament) and understand its role in the circuit.
Key Terms & Definitions
- Alternating Current (AC) — electrical current that reverses direction periodically.
- Auto Transformer — single coil transformer that selects the required kV.
- Rheostat — variable resistor used to adjust current (mA) to the filament.
- Step Up Transformer — increases voltage from auto transformer to kilovoltage.
- Step Down Transformer — decreases voltage and increases current for the filament.
- Rectifier — device converting AC to DC for the x-ray tube.
- Voltage Ripple — variation in output voltage; lower ripple is preferred.
Action Items / Next Steps
- Find and print multiple x-ray circuit diagrams; practice labeling all parts and identifying their function and position.
- Ensure you can label components as primary, secondary, or filament side.
- Be prepared to draw and explain the circuit order and function for exam questions.