POWER ELECTRONICS Instructor: Eng. Jalal Al Roumy The Islamic University of Gaza Faculty of...

POWER ELECTRONICS

Instructor: Eng. Jalal Al Roumy

The Islamic University of GazaFaculty of EngineeringElectrical Engineering Department

الرحمن الله بسمالرحيم

EELE 5450 — Summer 2012

Lecture 4

Chapter Two

Series and Parallel operation

In many applications, the power handling capability of a single power diode is not sufficient. (HVDC applications).

Chapter Two

Series and Parallel operation

Series and parallel combination of diodes are essentially for handling the high voltage and high current necessary in such applications.

Steady-state and transient voltages must be equally shared when diodes are connected in series.

When diodes are connected in parallel, each diode must share the total load current equally, both under transient and under steady state conditions.

Chapter Two

Series operation of diodes

Series-Connected Diodes

Chapter Two

Series operation of diodes

Series-Connected Diodes with Voltage Sharing

Chapter Two

Series operation of diodes

Is=Is1+IR1=Is2+IR2, IR1=VD1/R1, IR2=VD2/R2

Chapter Two

Series operation of diodes

More than two diodes

Chapter Two

Series operation of diodes

Series-Connected Diodes with Dynamic Voltage Sharing

Chapter Two

Example:Find the diode voltages if R1 = R2 =R = 100 kFind the voltage sharing resistances R1 and R2 for equal diode voltages

1 25 30 35S S SV kV I mA I mA

Chapter Two

Example: Find the diode voltages if R1 = R2 =R = 100 k1)Vd1=2750V2)Vd2=2250V

Find the voltage sharing resistancesR1 and R2 for equal diode voltages1)Let R1=100k2)R2= 125K

Chapter Two

Parallel-Connected Diodes

End of Lecture