unit 4-transformers

what do transformers

-changes the intensity of alternating voltage and current, to high to low intensities. -serves as single-phase circuit carrying 60-cycle (60HZ) AC

characteristics of closed core transformers

-closed core provide continuos path for magnetic flux -low magnetic energy is loss -laminated to prevent hinder eddy currents -the most commonly used is x-ray generation

closed core transformers

-heavy insulated coils (*windings*) are wound around a laminated square or circular ring or core to prevent transformer loss from eddy currents

characteristics primary coils

-input side -supplied w/alternating currents

characteristics secondary coils

-output side -develops AC by mutual induction

eddy current losses

-swirling currents causes by alternating magnetic flux in core of transformers by AC current. -produce heat in core by electrical power loss, which has to be replaced by transformer -contribute to loss of efficency

shell type transformers

-the most commercial transformer that consists of laminated core, pile of sheets of steel, having two holes, were 1st and 2nd coil are wrapped in the middle. -coils are insulted properly to increase maximum efficiency -the whole transformer is submerged in oil for insulation and cooling

what is located in the primary xray machine

1 Main switch 2 FUSES 3 autotransfromer 4 prereading kilovoltmeter 5 timer and exposure switch 6 remote control switch 7 timers: milliampere-second meter, AEC, BAck up timer 8. circuit breaker 9. filament circuit of xray tube 10. filament ammeter

high freqeuncy

1% voltage ripple

three types of losses of electrical power in transformers

1. copper losses 2.eddy current losses 3. hysteresis losses

what is located in the secondary xray machine

1.milliammeter 2.milliamoere-second meter 3. rectifier 4. xray tube

single pahse

100% voltage ripple

to find pluse of full wave

120 pluse X time=dot

three phase six pluse

14% voltage ripple

3 phase, 12 pluse

4% voltage ripple

if a single rect is place into a circuit that conducts 60HZ AC so that it suppresses the position portion of the waveform, the the output waveform will contain

60 negative pluses per second

to pulse of a 1/2 wave

60 x time=dot

semiconductor

A material that can sometime conduct an electric current and sometime not, depending on the voltage applied across that material.

Autotransformer

A type of transformer having a single winding.

Diode

An electrical device that contains two electrodes, passes current to in one direction: cathode to anode

effect of transformer law effect on current

IS/IP=VP/VS or IS/IP=VP/VS

why does xray circuit need retification?

In order that a reverse voltage is not applied across the x-ray tube. And x-ray tubes operate most efficiently on DC current.

what determine the rating of xray tube

KVP*TIme*MA

Is there physical contact b/t primary and secondary circuits of the xray machine?

No

the set up ratio:

Ns/Np

what does the prereading kVP meter allow

The precise adjustment of the supply voltage and monitoring the kVp before the x-ray exposure.

Power

The product of voltage and current. Watt.

primary purpose of autotransformer

To vary and control the amplitude of the voltage supplied to the high-voltage step-up transformer and the filament transformer.

equation of the transformer Law, *Voltage*

VS/VP=NS/NP

autotransformer equation:

Vs/Vp=#tapp turns/#primary turns

self recticfication

a circuit, that result in half-wave rectification

autotransformer

a device that varies input voltage to a transformer to control its output voltage

a semiconductor rect is

a solid state device

open core transformer

a transformer w/ two iron core wrapped in the coil, which becomes more efficient then air core

current that flows b/t high voltage transformer and rectifier

alternating

serves as a KV selector

autotransformer

what is registered by millimeter

average tube current

how do transformers transfer electrical energy from one circuit to the other

by electromagnetic mutual induction

how to prevent copper losses

by using a copper wire w/ adequate diameter

how to reduce eddy current and hysteresis

by using laminated cores

what does IS/IP=NP/NS or IS/IP=VP/VS mean

current in 2nd coil/current in 1st coil= #turns in 1st coil/#turns in 2nd coil or current in 2nd coil/current in 1st coil= voltage in 1st coil/voltage in 2nd

the emf induced in any coil is_______to the number of turns in the coil that cuts, is cut by, or links with, a given magnetic flux

directly proportional

why will a diode normally pass current in one direction

due to the NP junction

transformer law quote

emf induced in the 2nd coil is to the emf in the primary coil, as the number of turns in the 2nd coil is to the number of turn in the primary coil

requires four reticfies

full-wave rectification

since milliammeter is located in the high voltage curcuit side how can it be safety mounted in the control panel

grounding it

hysteresis losses

heat in the core produced by magnetic domains repeatedly arranging themselves in the windings due to AC

which principe of rectification produce produce maximum efficiency of xray production

high freq rect

advantages of halfwave over fullwave rectifaction

inverse flow is suppressed due to the production of tube

copper losses

loss of electrical power due to resistance of the coils in a transformer

primary circuit of an xray machine begins at_____and ends at the _______

mainswith/AC source, and primary side of step up transformer

step-up transformer

more turns in the secondary coil than in the primary put out a higher voltage, and decreases amperage in an inverse ratio

how does the autotransformer operate

operates on the principle of self induction, where a single coil serves as both the primary and secondary, with number of turns being adjustable

what causes current to flow in any curcuit

potential difference

rectification

processing of changing alternating current to direct current

a diode is another name for

solid state rectifier

the secondary voltage of the autotransformer is applied to...

the primary side of the main step-up transformer

during exposure, the amount of current passing through a diode compared to current passing through x-ray tube is

the same

in self recitation which structure suppresses the flow of current through the xray tube

the tube itself

disadvantage of open core transformers

there is some loss of power due to leakage of magnetic flux in the air at the end of the iron cores

rectifying systems are located b/t what two structures

transformer and xray tube

aircore transformers

use two insulted coil wires, laying side by side a primary and secondary coil

advantages of fullwave rectification supplied to xray tube

uses higher value because xray is protected more efficient power

what are the words for VS/VP=NS/NP

voltage in 2nd coil/Voltage in 1st coil= Number of turns in 1st coil/Number of turns in 2nd coil