POWER ELECTRONICS

Instructor: Eng. Jalal Al Roumy

The Islamic University of GazaFaculty of EngineeringElectrical Engineering Department

الرحمن الله بسمالرحيم

EELE 5450 — Summer 2012

Lecture 14

Chapter Five

Full-wave controller With Inductive Load

In actual practice most loads have some amount of inductance.Motors, solenoids, transformers, and even some resistive heaters have inductive components as apart of their impedance.

The effect of this reactance is that the rms-to-average-current ratio is lowered. Higher average current can be passed through the SCR.

With an inductive load , current flow is maintained through the SCR even after the input voltage has reversed polarity and goes negative. The duration of this interval is determined bu the load power factor.

Chapter Five

Full-wave controller With Inductive Load

Chapter Five

Full-wave controller With Inductive Load

Chapter Five

Ө > φ

Chapter Five

Ө < φ

Chapter Five

Triggering by pulse train synchronization

Chapter Five

Motor application

Chapter Five

Zero Voltage Switching

The control of rms ac voltage to the load could also be Achieved by changing the on and off periods of the ac Input wave to the load.

There are basically two methods of control:

On-off control Proportional control

Zero Voltage Switching

Synchronous tap changing

If a small variation of ac output voltage is required , then the taps of a transformer would be changed by switching thyristors in the proper manner.

End of Lecture