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| electric generator/ dynamo |
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Definition
a device that converts mechanical energy to electrical energy using faraday's discovery of moving flux lines in relationship to a conductor to induce current
composed of a conductor and magnets |
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Definition
| the source of the magnetic fields |
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conductor
rotation by a strong source of mechanical energy can produce massive amounts of electrical energy |
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Definition
| two metallic rings isolated from each other that rotate with armature and each connects with one end of armature |
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Definition
| metal strips which conduct current from the armature and transmit it to the external circuit |
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Definition
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Definition
| one complete turn of the generator armature |
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| level at which American and Canadian generators operate at |
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Definition
| consists of 2 alternations, one positive and one negative |
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Term
| average value of a half cycle |
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Definition
| .637 times the peak value |
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Definition
| max value of a given alternation measured from zero to peak |
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Definition
| the net voltage produced during full wave rectification |
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Definition
| the 2 armatures are 90 degrees out of phase |
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Definition
the three armatures are 120 degrees out of phase
most common in xray circuits |
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Definition
| made by exchanging slip rings for commutator rings |
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Definition
| a slip ring cut in half with each half connected to one end of the armature wire |
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Definition
transformers operate on AC to provide the changing magnetic field that induce voltage in secondary coil
less power loss in AC than Dc |
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Definition
| a device that changes the magnitude of voltage and current in an AC circuit |
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Definition
| transformers are composed of two coils placed near one another but without electrical connection |
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Definition
input side
connected to the source supplied with AC |
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Definition
output side
develops AC by mutual induction |
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Definition
| when the voltage is increased from the primary to the secondary |
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Definition
| when the voltage is decreased from the primary to secondary |
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Term
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Definition
the EMF induced in the 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
Vs/Vp= Ns/Np
used to find if stepping up or down |
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Term
| current and number of turns |
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Definition
current is inversely proportional to the number of turns
Ip/Is= Ns/ Np |
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Term
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Definition
| two coils of wire in proximity to facilitate induction |
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Term
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Definition
| the primary and secondary coils filled with an iron core which causes the strength of the magnetic field to increase induction |
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Term
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Definition
| closing the core will direct the lines of force from the primary to the secondary cores toward eachother and result in a significant increase in field strength |
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Definition
converges the inside and outside lines of force through an iron core
primary and secondary coils are wound atop one another and around the central section of the core for maximum efficiency |
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Definition
transformer efficiency is the ability of a transformer to avoid power loss
likely to be about 95% of more |
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Term
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Definition
caused by the inherent resistance to current flow that is found in all conductors
power lost due to this resistance is proportional to the square of the current
can reduce this loss by using low resistance, large diameter copper wire |
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Term
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Definition
results from currents opposing the cause which produced them, in accordance with Lenzs law
produced in any conducting material subjected to changing magnetic field
these useless currents produce heat in the core
reduced by laminating the transformer |
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Term
hysteresis loss
(lagging loss) |
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Definition
the transformer operates on and puts out AC
occurs because energy is expended as the continually changing AC current magnetizes, demagnetizes, and remagnetizes
this continuous reorientation of the magnetic dipoles requires energy and produces heat in the core thereby wasting electrical power
reduced by utilizing a laminated silicon iron core |
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Term
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Definition
process by which alternating current is changed to pulsating direct current
permits electron to flow easily in one direction while offering high resistance to movement in the other direction |
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Definition
| and electronic device that contains two electrodes |
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Term
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Definition
suppresses the opposing half of the incoming AC cycle (negative half cycle)
the opposing half of the flow is ignored, not utilized
one voltage peak per cycle
60 pulses per 60 Hz current |
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Term
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Definition
converts the opposing half of the AC cycle so that electrons are routed toward the cathode
negative cycle converted into a positve one
two voltage peaks per cycle
accomplished through 4 rectifiers in a bridge circuit
120 pulses per 60 Hz current
exposure times half those of half wave current |
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Term
| advantages of full wave rectification |
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Definition
permits significant increase in power output capability
larger exposures |
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Term
| disadvantages of full wave rectifiers |
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Definition
| using entire AC wave results in the production of a high percentage of low energy xrays |
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Term
| principal disadvantage of self rectification |
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Definition
low heat loading capacity of an xray tube so there is a danger of overheating the anode causing thermionic emission resulting in the second half of the cycle
this could break the filament and destroy the tube |
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Term
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Definition
the xray tube serves as a diode
during negative half cycle, the anode is negative and the cathode is positive
current will not flow because there is not a space charge near the anode
uses solid state diode rectifiers
made of semiconductors of which silicon most common
N type and P type |
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Term
| self/ tube rectified circuit |
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Definition
xray tube acts as rectifier
current only flows from cathode to anode
rarely seen |
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Term
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Definition
| have loosely bound electrons that are relatively free to move about inside the material |
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Term
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Definition
have electron straps
these positive traps (called holes) can also be viewed as being free to migrate through the material |
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Term
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Definition
when the negative terminal of the AC source is connected to the N end and positive terminal to the P end
reduces barrier voltage
allows current to flow across junction |
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Term
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Definition
positive terminal connected to N end and the negative terminal connected to the P end
electrons and holes move away from each other
increases barrier voltage
prevents current from flowing |
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Term
| determining rectifier failure |
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Definition
whenever one rectifier fails in a single phase four rectified system, it operates as a 2 diode rectifier
produces a drop in the milliampere reading to about 1/2 of normal value
appears under exposed |
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