The electric circuit of a standard X-ray machine consists primarily of three main circuits: the primary circuit, the secondary circuit, and the filament circuit.

These circuits work together to produce X-rays by powering and controlling the X-ray tube. Below is an overview of the circuit components and their functions:

Primary Circuit

• Power Supply & Line Compensator: Provides stabilized incoming voltage (usually 220 V AC) to the system.
• Autotransformer (kVp Selector): A variable transformer that adjusts the voltage by self-induction, allowing selection of the desired kilovoltage peak (kVp) which controls the penetrating power of X-rays.
• kVp Meter (Voltmeter): Measures the voltage that will be applied to the X-ray tube.
• Exposure Switch (Timing Circuit): Controls the duration of the exposure by completing or breaking the circuit, effectively turning X-rays on and off.
• Circuit Breaker: Protects the system by breaking the circuit during overload or fault conditions.

Secondary Circuit

• Step-up Transformer: Increases the primary voltage from volts to kilovolts (kV) needed to accelerate electrons in the X-ray tube to generate X-rays. It operates by mutual induction with two coils (primary and secondary).
• Rectifier Diodes: Convert the alternating current (AC) from the transformer to direct current (DC) required by the X-ray tube for consistent electron flow.
• mA Meter: Measures the tube current, which controls the number of electrons and, thus, the quantity of X-rays produced.
• Ground: Provides a safe path for stray electric charges.

Filament Circuit

• Step-down Transformer: Lowers the voltage to heat the filament in the cathode to produce thermionic emission (release of electrons).
• mA Selector (Ammeter): Allows adjustment of the current heating the filament, controlling the number of electrons produced.
• Focal Spot Selector: Determines the size of the focal spot on the anode target from which X-rays are emitted.

X-ray Tube

• Cathode: Heated filament emits electrons (thermionic emission) and focuses them into a beam.
• Anode: Positively charged target that accelerates and stops electrons, producing X-rays via interaction with the target material.