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Transformers

Radiologic Transformers

QuestionAnswer
Define transformer. An electromagnetic device changing AC from low voltage to high votage, and vice versa, with loss of an appreciable amount of energy.
Which current does a transformer work with (AC or DC)? AC
Define transformer law. The emf induced in secondary coil is to the emf in the primary coil, as the number of turns in the secondary coil is to the number of turns in the primary coil.
Name the 4 types of transformers. Air core, open core, closed core and shell type.
Define air core. Consists simply of 2 insulated coils lying side by side.
Define open core. Has iron core inserted into coil of wire; more efficient than the air core.
Define closed core. Provides continuous path for magnetic flux; more efficient than air and open cores.
Define shell type. Must be heavily insulated; most advanced and efficient transformer.
Define power loss. The power lost by transformers to heat; usually 5%.
What are the 3 types of power loss? Copper, Eddy Current and Hysteresis.
Define copper loss. Pertains to loss of electrical power due to resistance of the coils. (I2R)
Define eddy current loss. Swirling currents in core by electromagnetic induction.
Define hysteresis loss. Loss occurring as a result of changing magnetic fields by the AC in the windings. Reduced by laminated silicon steel core.
Define autotransformer. Device that varies input voltage to a transformer to control its output voltage.
What device serves indirectly as the kV selector? The autotransformer.
What are the 3 options that allow control of filament current? Choke coil, rheostat and high frequency (HF) circuit.
Which method of filament current control is old? Choke coil
Which method of filament current control is new? Rheostat
Define choke coil. Operates on principle of self-inductance and requires AC.
Define rheostat. Variable resistor designed to regulate filament current.
Define the formula for calculating secondary voltage using primary voltage, # primary turns and #secondary turns. Secondary voltage = Primary Voltage (x) # of Secondary Turns / # of Primary Turns
Define the formula for calculating secondary current using primary current, #primary turns and #secondary turns Secondary amperage = Primary Amperage (x) #of Primary Turns / # of Secondary Turns
Define the formula for calculating secondary voltage using primary voltage, TOTAL # of turns, # of tapped turns. Secondary Voltage = Primary Voltage (x) # of Tapped Turns / Total # of Turns
What are the 2 circuits found in an x-ray tube? FILAMENT circuit carrying needed current to heat filament and the TUBE circuit itself.
Define step-down transformer. When 2nd coil has FEWER turns than 1st coil, the OUTPUT voltage will be LESS than the INPUT voltage.
Define step-up transformer. When 2nd coil has more turns than 1st coil, and puts out a HIGHER voltage than supplied to it.
What is another name for transformer? X-ray generator
What is the difference between the primary coil and secondary coil? Primary coil is supplied with AC; secondary coil develops AC via mutual induction
Which coil (1st or 2nd) is the input side of the transformer? 1st coil (primary)
Which coil (1st or 2nd) is the output side of the transformer? 2nd coil (secondary)
Define the Law of Conservation of Energy. There can be no more energy coming out than is put in.
Which transformer is the most commonly used in x-ray generating equipment? Closed core transformer
Which transformer is the most commonly used commercially? Shell-type transformer
The rheostat replaced what device regulating filament current? The choke coil
What is used as the power source of most modern x-ray machines? 3-phase power supply
What concept does a transformer work off of? Mutual induction
Which type of current is used with transformers? AC
What principle does the AUTOTRANSFORMER work off of? Self induction
What is another name for the rheostat? Variable resister
Define mutual induction. Process of producing electricity in a secondary coil by passing an alternating current through a nearby primary coil.
How does a transformer change the intensity of alternating voltage and current? Via mutual induction
Which current (AC or DC) does a transformer operate with? AC
Tapping windings of the auto transformer to supply voltage to the step-up transformer is the purpose of what device? kVp Selector
How can hysterisis losses be reduced in a transformer? Lamination
When the technologist selects kilovoltage on the control panel, which device is adjusted? Autotransformer
If the voltage is stepped up, what happens to the current in the secondary side of the transformer? Decreases
What device would be used when the milliamperage is set on the control panel? Rheostat
What effect does adjusting the filament control have on the production of x-rays? It controls the quantity.
What type of current is supplied to the Radiology department? Alternating current
Created by: rad1958tech on 2008-02-29



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