Rad Tech 110 Circuits

Conditions Necessary X-ray Production High voltage In the kilovoltage range Electrons A supply of electrons A need to stop the electrons suddenly

Types of Transformers Shell type Core type

How do transformers work? They can only work using AC current On the principle of induction Mutual Self The basic premise is that AC current ‘induces’ alternating magnetic fields.

Transformers work? These alternating magnetic fields are distributed throughout the core of the transformer. The alternating magnetic fields ‘induce’ an electrical current in loops (coils) of wire.

What gets transformed? Both voltage and current In a step-up transformer the voltage is increased The primary side (incoming) has less coils than the secondary (outgoing) side. Because there are more coils on the secondary side a higher voltage is produced Increases voltage is reflected as a higher amplitude of the waveform.

This occurs due to the conservation of energy. At the same time as voltage increases the current correspondingly decreases. This occurs due to the conservation of energy. If you increase one aspect, voltage, you have to decrease the other, current. (Voltagep)(currentp)=(voltages)(currents)

Step down transformer Here the primary side has more coils than the secondary side. The result is a decrease in voltage through the transformer.

The X-ray Circuit

Three sections of the x-ray circuit Operating (control) console High voltage generator X-ray tube

Operating (control) console Line voltage compensator Autotransformer kVp selector mA selector Timer Pre-reading kVp meter

Line voltage compensator The purpose of the line voltage compensator is to maintain a constant voltage to the system. In the modern system this is done automatically.

Autotransformer The autotransformer works on the principle of self-induction. It has a single core and is responsible for varying the voltage. Because of its ability to adjust voltage, the autotransformer can be either a step-up or step-down transformer.

kVp selector kVp is adjusted at the autotransformer Taps are available so that different voltages can be achieved.

Pre-reading kVp meter The kVp meter is considered pre-reading because it is not actually measuring kVp but measuring voltage off the autotransformer. Remember, the autotransformer is used to adjust voltage.

Timer Historically, there have been many types of timers. Today, all timers are electronic timers of various types. mAs Phototiming (AEC) Regular electronic

mA selector Allows for adjust of the filament voltage Precision resistors Choke coil

High Voltage Generator Step-up transformer High voltage transformer High tension transformer Step-down transformer Filament transformer Rectifiers

Step-up Transformer This transformer is responsible for producing the high voltages necessary for x-ray production. Turns ratio of 500:1 or 1000:1

Filament Transformer Intended to lower voltage and increase current Allows for thermionic emission to occur at the filament Ultimately, provides the electrons necessary for x-ray production. Tube current measured in mA.

Rectifiers Current traffic cops Intended to allow electrons to flow in only one direction Provide the mechanism that converts AC to DC current. 4 rectifiers are required to fully convert AC to DC.

Types of Circuits Single phase Three phase Medium and High Frequency Full wave Half wave Three phase 6 pulse 12 pulse Medium and High Frequency Capacitor discharge Found predominantly in portables.

Single Phase Full Half

Three phase 6 pulse 12 pulse

Three phase transformers Three phase units use delta and ‘wye’ transformers 6 pulse 2 ‘wye’ and 1 delta 12 pulse 2 delta and 1 ‘wye’ They also require 12 rectifiers

Advantages of 3 phase Higher beam quantity and quality Higher mA stations are also possible

Why higher quantity and quality for three phase? Because the voltage ripple is less Basically when the tube is energized it stays energized. full 3 phase 12 pulse

Medium/High Frequency Generator