PHYS 101 - 2 - Three Phase Power and Control

Three Phase, Six Pulse

A three phase generator which has a ripple of 13-25%. The voltagenever drops below 75-87% and has 35% more average energy photons than single phase generators.

Three Phase, Twelve Pulse

A three phase generator which has a ripple of 4-10%. The voltagenever drops below 90-96% and has 40% more average energy photons than single phase generators.

200 to 240

Electricity is usually supplied to buildings in the United States by 60Hz AC with a nominal rms of ___ to ___ volts.

Electronic Timer

This is the most sophisticated and most accurate of the x-ray timers. They allow a wide range of time intervals to be selected and are accurate to intervals as small as 1 millisecond and most radiographic equipment today contain it.

Main Circuit

This is the portion of the x-ray circuit that modifies the incoming power to produce x-rays. This circuit must boost the voltage to the range necessary to produce x-rays and to permit the radiographer to adjust the amperage, voltage, and length of exposure.

Filament Ammeter

This measures filament current, hence the amount of heat developed in the filament.

Filament Circuit

This modifies the incoming line power to produce the thermionic emission from the filament wire of the x-ray tube by a sequence of devices.

Main Switch

This part of the primary circuit potentially protects the equipment and reduces fire hazard.

High Voltage Transformer

A step up transformer that increases the primary voltage to provide the high voltage required to operate the x-ray tube, the step up ratio being between 500:1 or 1000:1. It is found in the secondary circuit.

Line Voltage Monitor

It is connected in parallel across portion of the primary side of the autotransformer. It detects fluctuations in line voltage due to variations in power distribution and power consumption.

Primary Circuit ( Low Voltage Side) Secondary Circuit (High Voltage Side)

The two divisions of the main circuit in an x-ray circuit.

Field / Pickup Selection

These devices located near the x-ray film samples the radiation during exposure and produces an electrical signal proportional to the intensity of the radiation.

Photomultiplier Tube

This has the ability to produce a current that charges a capacitor.

150%

Backup times cannot exceed the tube limit and should be set at ______% of the anticipated manual exposure mAs.

Motor Principle

The result of the interaction of the magnetic fields when an electric current is sent along a conductor that is residing in a magnetic field.

Space Charge Compensator

This automatically lowers filament current as kV is increased or vice versa maintaining the tube current at a nearly constant rate and enables the technologist to change kV without producing appreciable effect on mA.

Filament Stabilizer

This corrects for the instantaneous fluctuations in line voltage that may be caused by momentary demand elsewhere on the line.

Voltmeter

This device measures in volts the differences of potential between any two points in a circuit and is always connected in parallel.

Ammeter

This device measures the quantity of electricity flow per second. It is connected directly into the circuit, which is in series and reads the same no matter where it is placed in a series circuit.

Potentiometer

It is another known name of the Rheostat.

Manual Backup Time

All AEC equipped units permit a ____________ to be set in cases where AEC is improperly set.

Minimum Reaction Time

All AEC have a _____________ which is determined by the length of time necessary for the AEC to respond to the radiation and for the generator to terminate the exposure.

Low Voltage Side

All of the radiographer-operated controls are located on the _______________ of the circuit to protect the operator from high voltage shock hazards.

Circuit Breakers

An equipment protection that is constructed to permit the breaking of the circuit before a dangerous temperature is reached. They simply pop open and can be reset once the cause of the problem has been located and removed from the circuit.

Fuses

An equipment protection that prevents prevent overloading in circuits. It is connected in series along the supply line and constructed with a metal tab that will melt when dangerously heated; thus breaking the circuit. It is not reusable it must be replaced when blown.

kVp Selector mA Selector Exposure Time Selector Rotor Switch Exposure Switch

Controls and meters located on the X-Ray Control Panel Console.

Kilovoltmeter

It indicates the desired kV and placed across the output terminal of the autotransformer, and actually reads voltage, not kilovoltage. It indicates kVp on the scale because of the known turns ratio of the high voltage step-up transformer.

Filament Control Device

It is also known as the mA selector.

Line Voltage Compensator

It permits adjustment of the line voltage to the correct value. It varies the number of turns on the primary side of the autotransformer until the compensator meter needle indicates that the correct line voltage has been restored; only then will the correct kV be obtained.

Density Control

It sets either small, medium or large settings according patient's size.

Milliammeter

Measures mA in the x-ray tube. Connected at the center of the secondary winding of the high voltage step up transformer to ensure safety. The secondary voltage is alternating at 60 Hz such that the center winding is always zero.

Vs/Vp = PT

The formula for the number of tapped turns or primary turns.

Autotransformer Law

The law that talks about the relationship of the voltage output to voltage input in an autotransformer.

.001 Seconds

The minimum reaction time of modern ionization timers.

.05 Seconds

The minimum reaction time of old phototimers.

Synchronous Timer

This uses a special type of electric motor known as the synchronous motor, which is a precision device designed to drive a shaft at precisely 60 revolutions per second. It cannot be used for serial exposures because they must be reset after each exposure, which requires too much time.

Automatic Exposure Controls

What does AEC stand for?

US Public Law 90-062

Which law mandates that generators must terminate the exposures at 600 mAs for exposures above 50 kVp and 2000 mAs for exposures below 50 kVp?

Ground Fault Circuit Interrupter

A device that protects both the equipment and people using an equipment. It replaces ordinary wall outlet, protects against electrical shock caused by electricity passing through your body to ground. Inexpensive and should be tested monthly.

Ground

A protective device that is grounded to protect the X-ray specialist and patient from electrical shock. Most electric sockets today are wired with three instead of two connections, the principal two are for the current carrying double wire and third contact is connected directly to earth.

mAs Timer

It is a special kind of electronic timer, which monitors the product of mA and time and terminates the exposure when the desired mAs is attained.

Filament Transformer

It is a step down transformer. The voltage supplied to this transformer is higher than the voltage supplied to the filament.

Autotransformer

It is also known as a variable transformer. It is used in radiographic units to regulate the voltage available to the primary side of the high voltage transformer .

Choke Coil

It is an electromagnetic device operating on the principle of self-induction; requires alternating current.

Tube Current

It is is measured in milliamperes by the milliammeter placed on the high voltage circuit, while an ammeter placed on the low voltage circuit measures the filament current.

Phototimers

It is often used to refer to all automatic exposure controls and uses a thyratron tube to regulate exposure automatically.

Three Phase Power

It is the multiple voltage waveforms that are superimposed on one another, resulting in a waveform that maintains a nearly constant high voltage.

X-Ray Tube

This is the last component of the filament circuit.

Ion Chamber

The type of automatic exposure control employed by most manufacturers incorporate a flat, parallel plate ionization chamber between the patient and the film.

Timer and X-Ray Exposure Switches

These switches control the current to the primary coil of the transformer, serving to complete the x-ray exposure.

Rheostat

This device permits a variable contact to slide along a series circuit of resistant coils. It functions in the same manner when used as voltage regulating device.

Secondary Circuit

This includes the secondary coil of the high voltage transformer and all of the devices to which it is connected electrically.

Galvanometer

This is a basic device for the measurement of current and voltage. It consists of a coil of fine copper wire suspended between the poles of a horseshoe magnet.

Timer Circuit

This is separate from the other main circuits of the x-ray machine. It consists of mechanical or electronic devices whose action is to "make" and "break" the high voltage across the x-ray tube.