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AC circuit breaker with series connected switches

AC circuit breaker with series connected switches. George G Karady. AC circuit breaker with series connected switches. CB’s protect power system Short circuit triggers the CB CB interrupts the inductive short circuit current

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AC circuit breaker with series connected switches

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  1. AC circuit breaker with series connected switches George G Karady

  2. AC circuit breaker with series connected switches • CB’s protect power system • Short circuit triggers the CB • CB interrupts the inductive short circuit current • After few cycle of arcing the current is interrupted at zero crossing

  3. AC circuit breaker with series connected switches Equivalent circuit • Supply is represented by Thevenin equivalent • Network open circuit voltage and short circuit impedance • Zshort = 1.8 ohm Vopen = 7.2 kV • Short circuit with zero fault impedance

  4. AC circuit breaker with series connected switches Equivalent circuit • CB with switches connected in series. • Snabber impedances are connected in parallel with each switch • Typical values :Capacitor = 0.1microF, Resistance = 10kohm. Total impedance Zsnub = 10k + 26ki ohm

  5. AC circuit breaker with series connected switches • The switches turn off in sequence • The voltage across the switch that turns off first is the largest

  6. AC circuit breaker with series connected switches • The equivalent circuit is: The voltage across the switch that turns off first is:

  7. AC circuit breaker with series connected switches • Voltage across the switch turns off first is: • Voltage across the switch is close to the supply voltage

  8. Rectifier with thyristors connected in series supplies a load

  9. Rectifier with thyristors connected in series supplies a load Rectifier supplies a load • Current path in the positive cycle • Snubber is connected in parallel with each diode

  10. Rectifier with thrystors connected in series supplies a load • Each thrystor is protected by a snubber connected in parallel • The current is determined by the load impedance • The voltage across the diode that turns off first is:

  11. Rectifier with thrystors connected in series supplies a load

  12. AC circuit breaker with series connected switches Switch 1 Switch 2 Switchingsequence • A diode and a snubber circuit is connected in parallel with each switches • In the positive cycle switch 1 turns off, • The current is transferred to the diodes and interrupted at zero crossing • Switch 2 turns off in the negative cycle to prevent conduction

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