Rectifier, Transformer & X-Ray Generator: Expert-Level Technical Quiz

Question 1

In a single-phase full-wave rectified X-ray generator connected to a 60 Hz mains supply, what is the ripple frequency applied across the X-ray tube?

Accepted Answer

120 Hz

Answer

60 Hz

Answer

180 Hz

Answer

240 Hz

Question 2

Which generator design typically produces the lowest voltage ripple under normal operation, leading to the most constant potential across the X-ray tube?

Accepted Answer

High-frequency inverter generator

Answer

Single-phase half-wave rectification

Answer

Single-phase full-wave rectification

Answer

Three-phase 6-pulse rectification

Question 3

Why is the filament circuit of an X-ray tube usually supplied by a separate step-down transformer rather than directly from the high-voltage secondary?

Accepted Answer

To provide low voltage, high current, and isolation at cathode potential

Answer

To increase rotor speed in the anode induction motor

Answer

To reduce tube housing leakage radiation

Answer

To stabilize line frequency during fluoroscopy

Question 4

In a three-phase 6-pulse X-ray generator, what is the principal reason the effective X-ray beam output is higher than in a single-phase full-wave unit at the same peak kVp and mAs?

Accepted Answer

The average tube voltage remains higher throughout the exposure

Answer

The focal spot becomes smaller during each pulse

Answer

The anode angle increases with phase overlap

Answer

The filament emits fewer low-energy electrons

Question 5

Which rectifier technology is most commonly used in modern X-ray generators because of its compact size, high efficiency, and suitability for high-frequency switching?

Accepted Answer

Solid-state silicon diodes

Answer

Mercury-vapor rectifiers

Answer

Selenium stacks

Answer

Gas-filled vacuum valves

Question 6

If the primary voltage of an autotransformer is reduced while all other control settings remain unchanged, what is the most immediate effect on the high-voltage transformer output?

Accepted Answer

The secondary voltage decreases proportionally

Answer

The ripple frequency doubles

Answer

The filament current rises sharply

Answer

The rectifier changes from full-wave to half-wave

Question 7

What is the main disadvantage of an autotransformer compared with an isolation transformer in the kVp selection stage of an X-ray generator?

Accepted Answer

It provides no electrical isolation between input and output

Answer

It cannot operate on alternating current

Answer

It requires rectification before voltage adjustment

Answer

It can only step voltage down, not up

Question 8

In a self-rectified X-ray circuit using a hot-cathode tube on AC, during which portion of the cycle are X-rays produced?

Accepted Answer

Only when the cathode is negative relative to the anode

Answer

During both half-cycles equally

Answer

Only near the zero-crossing intervals

Answer

Only when the cathode is positive relative to the anode

Question 9

Compared with a 6-pulse three-phase generator, a 12-pulse three-phase generator chiefly improves beam quality and output consistency because it:

Accepted Answer

Further reduces voltage ripple by phase-shifting and combining outputs

Answer

Uses a lower peak voltage with higher exposure time

Answer

Eliminates the need for a filament transformer

Answer

Produces fewer pulses per mains cycle

Question 10

Which statement best describes the relationship between transformer turns ratio and voltage in an ideal X-ray high-voltage transformer?

Accepted Answer

Voltage is proportional to the turns ratio

Answer

Voltage is inversely proportional to the turns ratio

Answer

Voltage is independent of the turns ratio at resonance

Answer

Voltage varies with the square of the turns ratio

Question 11

In high-frequency X-ray generators, why can the high-voltage transformer be made substantially smaller than in line-frequency designs?

Accepted Answer

High frequency allows less magnetic core material for the same power transfer

Answer

The rectifier removes the need for magnetic coupling

Answer

The filament transformer assumes part of the high-voltage load

Answer

The autotransformer directly energizes the tube without stepping up voltage

Question 12

What is the principal purpose of rectifying the output of the high-voltage transformer before applying it to the X-ray tube?

Accepted Answer

To maintain electron flow from cathode to anode in only one direction

Answer

To increase filament temperature without raising tube current

Answer

To synchronize rotor acceleration with line frequency

Answer

To compensate for off-focus radiation inside the housing

Question 13

For the same indicated kVp and mAs, which generator type generally yields the lowest radiographic exposure output because the tube voltage falls to zero twice each cycle?

Accepted Answer

Single-phase half-wave generator

Answer

Single-phase full-wave generator

Answer

Three-phase 12-pulse generator

Answer

Constant-potential high-frequency generator

Question 14

In older X-ray systems, mechanical timer inaccuracy became especially significant at very short exposure times primarily because:

Accepted Answer

A small error represented a large fraction of the intended exposure duration

Answer

Transformer hysteresis reduced kVp only during the final pulse

Answer

Rectifier polarity reversed before the rotor reached full speed

Answer

Autotransformer taps shifted under filament loading

Rectifier, Transformer & X-Ray Generator: Expert-Level Technical Quiz

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