Full wave rectification, half wave rectification, applications of rectification, three wave rectification, Hydrotherapy, electrotherapy, role of electrotherapy, advantages and disadvantages of electrotherapyy

1. Duration: 60 min DPT Medical Physics Lecture 07
Instructor:
Engr. Taimoor Muzaffar Gondal
taimoor.muzaffar@superior.edu.pk
Lecture 07

2. Duration: 60 min DPT Medical Physics Lecture 07
RECTIFICATION
The conversion of alternating current (AC)
to direct current (DC), this involves a
device that only allows one-way flow of
electrons.
The used for rectification is called a rectifier.

3. Duration: 60 min DPT Medical Physics Lecture 07
TYPES OF RECTIFICATION
Single-phase Rectifiers
 Half-wave rectification
 Full-wave rectification
 Full-wave bridge rectifier
Three-phase Rectifiers
 Three-phase, half-wave circuit,
 Three-phase, full-wave circuit using center-tapped transformer

4. Duration: 60 min DPT Medical Physics Lecture 07
Single-Phase Rectifiers
Single-phase rectifiers are in use both as low-power stand-alone converters (up to some kilowatts)
and as output stage in Switched Mode Power Supplies (SMPS). For domestic equipment.
The harmonic content of the rectifier's output waveform is very large and consequently difficult to
filter.

5. Duration: 60 min DPT Medical Physics Lecture 07
HALF-WAVE RECTIFICATION
Single diode rectifier is connected across an alternating voltage
source.
Since the diode only conducts when the anode is positive with
respect to the cathode, current will flow only during the positive
half cycle of the input voltage.
During the positive half cycle of the source, the ideal diode is
forward biased and operates as a closed switch.
The source voltage is directly connected across the load.
During the negative half cycle, the diode is reverse biased and
acts as an open switch.
The source voltage is disconnected from the load. As no current
flows through the load, the load voltage Vo is zero.
Both the load voltage and current are of one polarity and hence
said to be rectified.

6. Duration: 60 min DPT Medical Physics Lecture 07
 If we need to rectify AC power to obtain the full use of both half-cycles of
the sine wave, a different rectifier circuit configuration must be used. Such a
circuit is called a full-wave rectifier.
Half Wave Rectification

7. Duration: 60 min DPT Medical Physics Lecture 07
Full Wave Rectifier In which either positive or negative
portions are inverted so that the entire
signal has the same polarity.
 Consider the first half-cycle, when the
source voltage
 polarity is positive (+) on top and negative
(-) on bottom.
 At this time, only the top diode is
conducting; the bottom diode is blocking
current, and the load “sees” the first half of
the sine wave, positive on top and negative
on bottom.
 Only the top half of the transformer's
secondary winding carries current during
this half-cycle as in Figure

8. Duration: 60 min DPT Medical Physics Lecture 07
Multi-phase rectification
The higher the number of pulses:
 The better the utilization of the rectifier
 The lesser the ripple amplitude
 The higher the ripple frequency — this implies that filtering the ripple is
easier.
 Systems with a number of pulses higher than 12(normally obtained by
combining two three phase bridges) are not often used since their
advantages are compensated by their growing complexity.

9. Duration: 60 min DPT Medical Physics Lecture 07
Three phase Half Wave Rectifier
 Consists of a three phase transformer a star connected secondary three phase
transformer with three diodes connected to the three phases
 The neutral point ‘NTRL’ of the secondary is considered as the earth for the
circuit and is given as the negative terminal for the load.

10. Duration: 60 min DPT Medical Physics Lecture 07
Cont.
 The three-phase full-wave bridge rectifier is used where the required
amount of dc power is high and the transformer efficiency must be
high. Since the output waveforms of the half waves overlap, they
provide a low ripple percentage. In this circuit, the output ripple is
six times the input frequency.
 If the 3-phase AC supply is fed via a transformer with a center
tapped is called three phase center-tapped transformer . This rectifier
requires six diodes.

11. Duration: 60 min DPT Medical Physics Lecture 07
ADVANTAGE AND DISADVANTAGE FULL
WAVE BRIDGE RECTIFIER
 ADVANTAGE:
 Need for center tap Xformer is eliminated.
 PIV is one half of that of center tape circuit.
 Output is twice than that of center tap circuit.
 DISADVANTAGE:
 Requires 4 diodes.
 Internal resistance voltage drop is twice than that of center tap
circuit.

12. Duration: 60 min DPT Medical Physics Lecture 07
• The use of the electrical current or energy as the use of medical
treatment.
• Electrotherapy modalities are the machines that the physiotherapist are
used for the purpose of the PAIN RELIEF and HEALING.
Electrotherapy

13. Duration: 60 min DPT Medical Physics Lecture 07
History of Electrotherapy
 The first recorded treatment of patient by electricity was by GOTTLOB
KRUGER in 1743
 The first medical treatment with electricity is recorded in London at
MIDDLESEX HOSPITAL, but the therapeutic is not clear
 GOLDING BIRD brought the electrotherapy in used at many hospitals.
 In 1831 FARADAY’S discover the electromagnetic induction, which can play
an important role in the electrotherapy.
 By the mid of 19th century many large hospitals had the electrical
departments with the LEYDEN JARS and batteries.

14. Duration: 60 min DPT Medical Physics Lecture 07
Energy Sources
The source of energy will in the form of:-
 Electricity
 Thermal energy
 Electromagnetic fields
 Light waves
 Lasers
Current used in Electrotherapy
 Direct current (monophasic)
 Alternating current (biphasic)
 Pulse current (polyphasic)

15. Duration: 60 min DPT Medical Physics Lecture 07
Electrotherapy devices are come in varieties some popular are:
Ultrasounds
TENS
Interferential current
Electrical muscle stimulator
Lasers
Devices of Electrotherapy

16. Duration: 60 min DPT Medical Physics Lecture 07
Increase in the blood circulation.
Increase the healing process.
Pain relief.
Reduce muscles spasm.
Increase the range of motion.
Increase the muscle strength .
Decrease spasticity of muscles.
Relaxation of muscle spasms.
 Prevention and retardation of disuse atrophy.
 Increase of local blood circulation.
 Muscle rehabilitation.
 Re-education electrical muscle stimulation.
 Maintaining and increasing range of motion.
Advantages

17. Duration: 60 min DPT Medical Physics Lecture 07
Over infected or cancerous tissue.
Over the dorsum of important women.
Too besides on sensitive areas (such equally testicles)
It could be a cause to an allergic peel irritation nether the pads or hurting from the
electrical charge. But these side effects are very rare.
Disadvantages

18. Duration: 60 min DPT Medical Physics Lecture 07
End of Lecture 07
For any kind of queries and questions you are advised to
write at
taimoor.muzaffar@superior.edu.pk
Or visit my office during consulting hours
This lectures can also be downloaded from
https://www.slideshare.net/Taimoor_Gondal