Quiz 7 full (RADS 354)

Rectification

Process of converting AC to DC

X-ray tubes operate most effectively on...

direct current (DC), but can on AC

Transformers are necessary for...; and operate on...

production of high voltage; AC

The high voltage AC supplied by the secondary side of the HT can be changed to DC by...

-suppressing the half of the AC cycle below the line (negative half) or changing the negative half cycle to a positive one

What is the location og the rectifying system?

between the secondary coil of the HT and the x-ray tube

Primary Types of Rectification

Self Rectification and Vacuum Tube/ Solid State Rectifiers

Simplest Type of Rectification

self-rectification

self-rectification

when high voltage is applied directly to the terminals (electrodes) of the x-ray tube it allows passage of electrons only when anode is positive in respect to cathode

During the negative half cycle of self rectification, the anode and cathode...

reverse charge causing no current to flow cause there is no space charge near the anode

Self Rectification is used in...

small mobile equipment

Self Rectification produces...

60 impulses per second, w/ 1 x-ray pulse with a max duration of 1/120 second every 1/60 second

Valve Tube (Vacuum Tube)

a thermionic diode tube, which resembles an x-ray tube only allowing current to pass in one direction

-designed to prevent production of x-rays

the valve tube has been replaced by...

solid-state rectifiers

Conduction Band

allows the free movement of electrons

Forbidden Band

allows no electron movement

With the semicondtor the gap is so small that electrons may...

jump the forbidden gap to get to the conduction band

Solid State Rectifiers are composed of...

crystals of semiconductors primarily silicon

Two types of silicon used to make rectifiers:

N-type & P-type

Silicon is a...

semiconductor with 4 loosely bound valence electrons (unstable)

N-type silicon is made by adding...

arsenic to silicon, as there will be an extra electron when combining the two

P-type silicon is made by adding...

gallium to silicon, as there will be one less electron when combing the two

Arsenic has how many valence electrons?

5

Gallium has how many valence electrons?

3

Behavior of N-type SIlicon

the electrons will drift in an electrical circuit, it behaves as a conductor

Behavior of P-type Silicon

when connected to an electrical current, there will be no flow of electrons

N-type and p-type silicone are connected together to form a:

solid-state rectifier

When solid state rectifier is connected so N-type silicon is connected to the negative source...

the electrons will flow (foward based diode)

When a solid-state rectifier is connected so that the p-type silicon is connected to the negative source...

no electrons will flow (reverse based diode)

Valve tubes or solid-state rectifiers will only allow current to flow in ____ direction.

one

Anodes (+) of the valve tube or p-type silicon of solid-state rectifiers are connected to the _____ of the x-ray tube.

cathode

Cathode (-) of the valve tube or the n-type of the solid-state rectifiers are connected to the ____ of the x-ray tube.

anode

Regardless of the polarity, the electron current always reaches the x-ray tube in...

the same direction

For Valve tube rectification, anything less than 4 valve tubes will result in...

half wave rectification

Solid-state rectification always results in...

full wave rectification, unless a problem

Solid state rectifiers are reffered to as..

diodes

Modules

individual diodes connected in a series that can withstand 1000 volts

Advantages of Solid State Rectifiers

-compact size

-no filament necessary

-long life due to ruggged contruction

-low foward voltage drop

-low reverse current

150 kV generator will have how many modules?

150 modules