Presentation on theme: "SELF INDUCTION DURING AC FLOW, MAGNETIC FIELD IS NOT CONSTANT. AN OPPOSING ACTION WITHIN THE COIL IS PRODUCED."— Presentation transcript:
SELF INDUCTION DURING AC FLOW, MAGNETIC FIELD IS NOT CONSTANT. AN OPPOSING ACTION WITHIN THE COIL IS PRODUCED
SELF INDUCTION INDUCED VOLTAGE IN AC CIRCUIT WILL OPPOSE THE SOURCE VOLTAGE IF THE SOURCE OF EMF INCREASES, THE INDUCED COIL VOLTAGE WILL OPPOSE IT AND ATTEMPT TO REDUCE IT. IF THE SOURCE OF EMF DECREASES, THE INDUCED COIL VOLTAGE WILL ATTEMPT TO INCREASE IT. LINE VOLTAGE COMPENSATOR WHICH TAPS OFF OF THE AUTOTRANSFORMER IN THE X-RAY CIRCUIT
MUTUAL INDUCTION IT IS NOT NECESSARY TO PHYSICALLY MOVE A MAGNET TO PRODUCE A CURRENT FLOW THE INTENSITY OF THE MAGNETIC FIELD, IF IT CHANGES, WILL PRODUCE A CURRENT FLOW HOW DOES THIS WORK?
Placing an electromagnetic near the coil and alternating the current through the electromagnet. Therefore, mutual induction can only be generated with AC.
TRANSFORMERS Transform potential and current energies to higher or lower intensities using electromagnetism. Operate only on AC current Transformers change the magnitude of current and the voltage in AC circuit Step-up transformer Step down transformer
TYPES OF TRANSFORMERS CLOSED CORE “SQUARE DOUGHNUT OF MAGNETIC MATERIAL
Autotransformer Single iron core with only one winding Acts as both primary and secondary Works on self induction Used for line voltage compensator by stepping up voltage or stepping down voltage as needed Not suitable as a high voltage transformer
SHELL TYPE TRANSFORMER “TRAPS” MORE MAGNETIC FIELD LINES IN PRIMARY WINDOW MORE EFFICIENT USED IN X-RAY EQUIPMENT
ELECTROMAGNETISM AS IT APPLYS TO X-RAY UNITS AUTOTRANSFORMER=SELF INDUCTION (BASED ON LENZ’S LAW) LINE VOLTAGE COMPENSATOR IS TAPPED OFF OF THE AUTOTRANSFORMER KVP MAJOR AND MINOR ARE TAPPED OFF OF AUTOTRANSFORMER
Step up transformer: converts Voltage to Kilovoltage Step down transformer: reduces voltage but increases current to supply to the filament (x-ray filaments need between 3-6 amps to heat up and “burn off” number of electrons for the mA station selected)
Rectifiers Changes AC to DC X-ray units require AC current for transformers X-ray Tubes need DC current
RECTIFIERS Electronic device (diodes) Located between secondary side of step- up transformer and x-ray tube Vacuum-tube Type Solid State Diodes
X-ray unit Line Voltage Compensator Autotransformer (increases voltage 100- 400) Adjusts and reads voltage Has a # of connections located along its length
High voltage generator High voltage transformer converts low voltage into kVp needed for production of x-rays Filament transformer Rectifiers
TRANSFORMER LOSSES OR INEFFICIENCY Resistance : current and copper wire hysteresis: alternating reversal of magnetic field eddy current: (Lenz’s law) currents that oppose the changing magnetic field causes loss in efficiency (page 102-103)