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Questions and Answers
What is the primary purpose of a high tension transformer in an x-ray machine?
Which transformer type is used to supply the filament circuit and ensure thermionic emission occurs?
In the context of mutual induction, what causes an electromotive force (E.M.F.) to be induced in one coil?
How does an autotransformer function within an x-ray machine?
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What is the relation between the primary and secondary winding numbers in a step-up transformer?
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What is the primary function of a high tension transformer in an x-ray machine?
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How does an autotransformer function in an x-ray machine?
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What is the role of a filament transformer in the x-ray system?
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What is a key characteristic of transformers in an x-ray machine?
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What is the main function of the high tension transformer as mentioned in the content?
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Which transformer is located within the control panel of the x-ray machine?
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Which of the following describes a benefit of using a filament transformer?
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What does the term 'radiation quality' in x-ray systems refer to?
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Which factor influences both radiation quantity and quality in an x-ray system?
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What is measured by the HVL in x-ray systems?
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Study Notes
Principle of operation
- Based on mutual induction
- An electromotive force (EMF) is induced in a coil
- When current in a neighboring coil changes
Constructional detail: Shell type
- Windings are wrapped around the center leg of a laminated core
Core type
- Windings are wrapped around two sides of a laminated square core
Transformers in x-ray machine
-
High tension transformer:
- Step-up transformer
- Primary winding number lower than secondary winding
- Supplies the anode circuit
- Responsible for producing high voltages needed for X-ray production
- Typical turns ratio 1:500 or 1:1000
-
Filament transformer:
- Step-down transformer
- Secondary winding number lower than primary winding
- Supplies the filament circuit
- Low voltage and high current
- Allows thermionic emission to occur at the filament
-
Autotransformer:
- Single-coil transformer
- Provides means for kVp selection
- Supplies power to other parts of the X-ray circuit
- Tube current is approximately 3 to 5 amps, depending on the filament temperature
Autotransformer – Example Calculation
- Transformer input voltage (vin)
- Output voltage (vout) can be switched between 0 and 120 VRMS
- Turns ratio is 1500
- Formula:
vout/vin = NS/NP = turns ratio - Rearranging the formula:
vout = vin × turns ratio - Substitute:
vout-min = 0 V × 1500,vout-max = 120V × 1500 - Answer:
vouthas a range of 0 V to 180,000 V (RMS)
Autotransformer Continued
- Consists of a single coil of wire wrapped around an iron core
Operating Console
- Console controls voltage (kVp) and current (mAs)
-
Radiation quantity:
- Total number of X-ray photons in the diagnostic beam
- Depends on kVp and mAs
- Usually expressed in mR or mR/ mAs, where R = roentgen (for US systems)
- Also expressed as ionizing charge per unit mass of air (SI unit), with 1 R = 2.58 10-4 C/kg
-
Radiation quality:
- Refers to the penetrating ability of the X-ray photons
- Determined by kVp
- Measured by HVL (Half Value Layer)
Mains Power
- Mains power in the UAE is 220 VRMS
- An X-ray set requires a large DC voltage
- Generated from mains by rectification, amplification, and smoothing
- Power system can be single-phase or 3-phase
Transformers in X-ray Machine
- High tension transformer and filament transformer are inside the high tension tank
- Autotransformer located in the control panel
Transformer
- An AC device used to change high voltage, low current AC into low voltage, high current AC and vice versa without changing the frequency
- It transfers electrical power from one circuit to another without a change of frequency
- It accomplishes this by electromagnetic induction
- There is no voltage loss in the remaining parts of the circuit
- Formula:
vout/vin = NS/NP = turns ratio - To power a 125 kVp x-ray tube, the transformer windings ratio is 403
Rectification
- Converts AC voltage to a unidirectional voltage (all positive)
- Done using a full-wave rectifier (diode bridge)
- In the UAE, the period of the mains power is 1/50 seconds
Process of Rectification
- Conversion of AC to DC
- Half-wave rectification
- Full-wave rectification
- Dedicated circuits
- Contain diodes:
- Semiconductor
- Thermionic
- Power rating: Supply current to circuits
- Contain diodes:
Half-wave Rectification
- Only the positive half-cycle of the AC supply is allowed to pass
Half-wave Rectifier Circuit
- Simple! Single diode
- ‘Load’: DC circuit; not truly getting DC
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Description
Explore the role of different transformers used in X-ray machines. This quiz covers high tension, filament, and autotransformers, including their operational principles and construction details. Test your knowledge on how these transformers function and contribute to X-ray production.
