Physics Transformers
Voltage is decreases from primary to secondary coil.
Step-down transformer
Voltage is increases from primary to secondary coil.
step-up transformer
Are laminated transformer cores more efficient than unlaminated ones?
yes
A transformer operates on
on AC but not on DC
If a transformer is supplied with 200 V to the primary coil, has 200 turns of wire on the primary coil, and 40,000 turns of wire on the secondary coil, what will the voltage be in the secondary coil?
x/200=40,000/200 40,000 V or 40 kV
If a transformer has 1,600 turns of wire on the primary coil, 110 volts in the primary coil, and 10 volts in the secondary coil, how many turns of wire must there be in the secondary coil?
10/110=x/1600 145.45 turns
What are transformers composed of?
2 coils placed near one another without electrical connection
An autotransformer:
Contains a single coil that serves as both primary and secondary coils
What is Eddy Current Loss a result of?
Currents opposing the cause which produced them (Lenz's Law)
What causes Copper Loss?
Inherent resistance to current found in all conductors
What is the formula for change in voltage?
Ns/Np
What is the formula for the Transformer Law?
Vs/Vp = Ns/Np
A transformer with a turns ration of 1000:1 is
a step-up transformer
Which type of transformer configuration has no core?
air core
What are the 4 types of transformer configurations?
air core, open-core, closed-core, and shell-type
primary to secondary coupling in a transformer is enhanced by
an iron core
Where is Eddy current loss produced?
any conducting material exposed to changing magnetic fields
capacitors are charged by
applying DC to the plates
connected between the source of AC and the primary side of a step-up transformer in x-ray
autotransformer
capacitors in mobile x-ray units supply a
burst of constant voltage
has the ability to deliver the charge in controlled intervals
capacitor
2 metal plates oppositely charged allowing storage of the electrons with dielectric insulation between the plates
capacitors
accumulates and stores electrical energy
capacitors
What is a transformer?
device that changes the intensity of alternating voltage
Voltage and number of turns
directly proportional
What can be used to minimize hysteresis loss?
ferromagnetic silicon iron
used to decrease the incoming line-voltage to 5-15V and 3-5 ampere range used to heat the x-ray tube filament
filament step-down transformer
What is the secondary coil supplied with?
induced current
voltage and amperage
inversely proportional
Which of the following is a transformer design used in x-ray imaging system?
shell type
Which transformer configuration confines lines of the primary coil and the secondary coil is wrapped around the primary with 2 closed cores?
shell-type
Ability to avoid power loss
transformer efficiency
A transformer "transforms" or changes electric
voltage
A transformer has 300,000 turns on the secondary side. The primary side has 600 turns. What is the turns ratio?
300,000/600= 500:1
What 2 laws combined allow for the calculation of the effect that the transformer has on amperage, voltage, and number of turns?
Ohm's Law and Transformer Law
three important transformers in the x-ray circuit
autotransformer, high-voltage step-up transformer, and filament step-down transformer
Why does hysteresis loss occur?
because energy is changing as the AC magnetizes, demagnetizes, and remagnetizes the armature
What is directly proportional to the ratio of the number of turns of the secondary coil to the number of turns of the primary coil?
change in voltage
The principal application of a transformer in an x-ray imaging system is to
change voltage
Which transformer configuration directs the lines of force from primary to secondary cores towards each other and increases field strength?
closed-core
what is the transformer that looks like a square donut called?
closed-core
3 Main factors effecting transformer efficiency
copper loss, hysteresis loss, and eddy current loss
What is the primary coil supplied with?
current
Raises the incoming line to kv
high-voltage step-up transformer
number of turns and amperage
inversely proportional
When a transformer is designed, the change in current is:
inversely proportional to the turns ratio
What reduces Eddy currents?
laminated transformer cores
autotransformers are used on the _______ side in a x-ray circuit before it has been increased by a step-up transformer
low-voltage
The output current in a step-up transformer is
lower than the input current
Transformers have iron cores to intensify the
magnetic field
What 2 principles do transformers function on?
mutual induction and ohm's law
If DC is applied to the primary coil of a step-up transformer, what is the result in the secondary coil?
nothing
the turns ratio is defined as
number of secondary windings divided by primary windings
What does n represent?
number of turns of wire
in Which type of transformer configuration are the primary and secondary coils filled with an iron core?
open-core transformers
What does V represent?
potential difference in volts
proportional to the square of the current
power loss
power input equals
power output
What does residual magnetism cause?
remagnetization to lag and produce more heat loss
The transformer changes
the amplitude of the voltage
When a step-up transformer is in use:
the secondary voltage is greater than the primary voltage
If a transformer produces a large secondary current from a small primary current:
the turns ration will be less than 1
How can you minimize Copper loss?
use low-resistance wire, high voltage, and low amperage