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‫بسم هللا الرحمن الرحيم‬
The Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
POWER ELECTRONICS
EELE 5450 — Fall 2009-2010
Instructor: Eng.Moayed N. EL Mobaied
Lecture 11
Chapter Four
The Single-Phase Full-Wave Phase-Controlled Converter
Using the Bridge Principle
Center-tap transformer (essential)
Chapter Four
The Single-Phase Full-Wave Phase-Controlled Converter
Using the Bridge Principle
When the input transformer is not essential, a bridge system is
often more economical.
There are several variations of the bridge circuit using one
thyristor , two thyristors, or four thyristors.
There are five different circuits of single-phase controlled
bridge. All the circuits are shown with inductive load.
Chapter Four
1-Circuit with two thyristors and two diodes
This circuit is not acceptable with inductive load. The inductive load
energy would free-wheel through D1
: and Th1 or D2 and Th2.
With high L/R ratio (time constant) ,the thyristors will forces to
conducts with out trigger pulses.
Chapter Four
2-Bridge with two thyristors and two diodes ,plus a freewheeling diode.
In this case , the free-wheeling diode (being of lower impedance than a
thyristor and diode in series),D3, allows the circulation of the stored
energy of the load. Also in the transient (during off state) D3 clamps the
transient voltage, so the thyristors do not see any high voltage spikes.
Chapter Four
3-Bridge with two thyristors and two diodes .
In this case , the energy in the load inductance circulates through diodes
D1 and D2 when the thyristors are not conducting.
Hence the two diodes of the bridge act as free-wheeling rectifires.
Current duty in the diodes is large.
Chapter Four
4- One thyristor and five diodes in abridge connection.
In many phase-rectifier dc motor drives this configuration of the bridge.
The rectified full-wave voltage is then controlled by thyristor Th1.
Used in Dc motors control.
Chapter Four
5- Bridge circuit with four thyristors.
Only, between the above circuit, this circuit can contains negative
voltage.For α<90 rectifier. For α>90 as inverter. (if L is large)( ch7)
End of Lecture **** Eng.moayed