The control of electric motor drives requires control of electric power. Power electronics have
eased the concept of power control. Power electronics signifies the word power electronics
and control or we can say the electronic that deal with power equipment for power control.
Main power source
Ref signal
Power electronics based on the switching of power semiconductor devices. With the
development of power semiconductor technology, the power handling capabilities and
switching speed of power devices have been improved tremendously.
Power Semiconductor Devices
The first SCR was developed in late 1957. Power semiconductor devices are broadly
categorized into 3 types:
1. Power diodes (600V,4500A)
2. Transistors
3. Thyristors (10KV,300A,30MW)
Thyristor is a four layer three junction pnpn semiconductor switching device. It has 3
terminals these are anode, cathode and gate. SCRs are solid state device, so they are compact,
possess high reliability and have low loss.
Control
Circuit
Digital
Circuit
Power
Electronic
circuit
Load
Feedback Signal
SCR is made up of silicon, it act as a rectifier; it has very low resistance in the forward
direction and high resistance in the reverse direction. It is a unidirectional device.