INDUSTRIAL ELECTRONICS “Your attitude determines your attitude.”
II. INDUSTRIAL ELECTRONIC DEVICES 1. ELECTRON TUBES a. Thyratron b. Ignitron 2. THYRISTOR a. Silicon Controlled Rectifier (SCR) b. Triac 3. BREAK-OVER DEVICES a. Shockley Diode b. Silicon Unilateral Switch c. DIAC d. Silicon Bilateral Switch (SBS) e. Silicon Controlled Switch (SCS) f. Gate Turn Off Switch g. Unijunction Transistor (UJT) h. Programmable Unijunction Transistor (PUT)
ELECTRON TUBES a. THYRATRON A gas filled triode used as an electrode switch. Giant GE Hydrogen Thyratron, used in pulse radars
ELECTRON TUBES b. IGNITRON Electron tube containing mercury and function as a rectifier. IGNITRON 1. Anode 2. Cathode 3. Ignitor 4. Mercury 5. Ceramic Insulators 6. Cooling Fluid
THYRISTOR Solid state devices used as a switch in applications that handles larger voltage and currents. Have at least four semiconductor layers. Regenerative switching devices and cannot operate in linear manner.
SCR Basic Construction and Equivalent Circuit SCHEMATIC SYMBOL
SCR CHARACTERISTIC CURVE
THYRISTOR V BR - BREAK-OVER VOLTAGE Voltage through which SCR starts to conduct when gate current is zero. I H - HOLDING CURRENT Anode current between the conducting state and non- conducting state.
Turning ON an SCR Apply enough gate triggering current. Apply anode voltage equal to break-over voltage. Turning OFF an SCR Anode current interruption Forced commutation
THYRISTOR b. TRIAC Triode AC A three-terminal device used to control the average current flow to a load. Can conduct current in either direction when it is turned on so it is called a bidirectional triode thyristor. Acts like two SCR’s connected in inverse parallel so that each SCR conducts alternately for every half cycle of an AC signal. Gated DIAC
TRIAC Schematic and Construction Diagram
ELECTRICAL CHARACTERISTICS OF TRIAC 1 . Maximum Allowable Main Terminal RMS Current 1 A, 3 A, 6 A, 10 A, 15 A and 25 A 2. Breakdown Voltage Highest main terminal peak voltage the triac can block in either direction typically 100 V, 200 V, 400 V and 600 V 3. On Stage Voltage Across the Terminals Ideal value is 0 V Typical value is 1-2 V
No contact bounce No arcing across partially opened contacts Operates much faster More precise control element ADVANTAGES OF TRIAC OVER MECHANICAL SWITCHES
BREAK-OVER DEVICES Small thyristors which do not switch the main load current. Useful as triggering devices.
BREAK-OVER DEVICES gate
You've reached the end of your free preview.
Want to read all 114 pages?
- Fall '16