TABLE OF CONTENTS The development of solid-state motor drive packages over the last 30 years has revolutionized the application of electric motors. Any power control problem can be solved using them. The solid-state drives allowed dc motors to run from ac power supplies or ac motors from dc power supplies. The frequency of ac power can be changed to any other frequency.
Furthermore, the reliability of solid-state drive systems has increased while their costs have decreased. The versatility of these solid-state controls and drives has provided many new applications for ac motors which were formerly covered by dc machines. The application of solid-state drives has also provided flexibility for dc motors.
The development and improvement of high-power solid-state devices have caused this major change.
The most important types of semiconductor devices are
The diode
The two-wire thyristor (or PNPN diode)
The three-wire thyristor [or silicon controlled rectifier (SCR)]
The gate turnoff (GTO) thyristor
The DIAC
The TRIAC
The power transistor (PTR)
The insulated gate bipolar transistor (IGBT)
A diode is a semiconductor device that conducts current in one direction only (Fig. 9.1). The current is conducted from its anode to its cathode, but not in the opposite direction. Figure 9.2 illustrates the voltage-current characteristic of a diode. A large current flows when a voltage is applied to the diode in the forward direction.
The current is limited to a...
