PROTECTION CIRCUIT OF SCR

OVERVOLTAGE
OVERCURRENT
DV/DT
DI/DT

1. PROTECTION OF SCR MODULE 2.3

2. PROTECTION OF SCR OVERVOLTAGE OVERCURRENT Dv / dt Protection of SCR Di/ dt Protection of SCR HEATSINK

3. dv/ dt Protection of SCR When the SCR is forward biased, junctions J1 and J3 forward biased and junction J2 is reverse biased. This reverse biased junction J2 exhibits the characteristics of a capacitor. Therefore , if the rate of forward voltage applied is very high across the SCR, charging current flows through the junction J2 is high enough to turn ON the SCR even without any gate signal.This is called as dv/ dt triggering of the SCR which is generally not employed as it is false triggering process . Hence, the rate of rise of anode to cathode voltage, dv/ dt must be in specified limit to protect the SCR against false triggering. This can be achieved by using RC snubber network across the SCR.

4. RC snubber network across the SCR

5. Di/ dt Protection of scr

6. Class E Commutation-

7. Crowbar ckt

8. H eatsink Heatsink Requirements SCR's emit about 1.5 watt's of energy in the form of heat, per ampere conducted. Failure to dissipate this energy is perhaps one of the main sources of SCR failure. ... Typically an aluminium heatsink, with fins to increase the surface area, is used to dissipate this energy to air.

9. BOOKS M.D. Singh and K. B. Khanchandani , “Power Electronics”, Tata Mcgraw Hill Website: https://www.electronicshub.org/scr-protection/

10. Practice Waveform

11. DAY 7 END Thankyou