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The effect of over-voltages on SCR are minimized by using
Answer: c Explanation: Varistors are non-linear voltage clamping devices, RC circuits across the loads can also be used.
Answer: c
See lessExplanation: Varistors are non-linear voltage clamping devices, RC circuits across the
loads can also be used.
Figure below shows SCR having dv/dt and di/dt protection, when the switch(shown in green) is closed the current through Rl =
Answer: a Explanation: As soon as the switch is closed, C acts like a S.C & the voltage equation gives Vs = (Rs + Rl) I + L di/dt Solve the above D.E.
Answer: a
See lessExplanation: As soon as the switch is closed, C acts like a S.C & the voltage equation
gives
Vs = (Rs + Rl) I + L di/dt
Solve the above D.E.
dv/dt protection is provided to the SCR by
Answer: c Explanation: Snubber circuit R-C in parallel with SCR is connected for dv/dt protection
Answer: c
See lessExplanation: Snubber circuit R-C in parallel with SCR is connected for dv/dt protection
The dv/dt protection is provided in order to
Answer: c Explanation: Accidentally some voltage spike or noise may occur in the vicinity of the device, if the magnitude is large enough it may turn on the SCR.
Answer: c
See lessExplanation: Accidentally some voltage spike or noise may occur in the vicinity of the
device, if the magnitude is large enough it may turn on the SCR.
The local hot spot formation in the cross-section of the SCR is avoided by
Answer: b Explanation: Applying the higher gate current spreads the ions quickly and avoids hotspot formation.
Answer: b
See lessExplanation: Applying the higher gate current spreads the ions quickly and avoids
hotspot formation.
di/dt protection is provided to the thryistor by
Answer: b Explanation: By placing the di/dt inductor (L) in series with the load, the change in the anode current can be limited to a small value
Answer: b
See lessExplanation: By placing the di/dt inductor (L) in series with the load, the change in the
anode current can be limited to a small value
The maximum rms current of an SCR is 50 A. For a 120° sine wave conduction the form factor (FF) = 1.878 Find the average on-state current rating (ITAV).
Answer: c Explanation: Thermal resistance always has the unit degree temperature per watt
Answer: c
See lessExplanation: Thermal resistance always has the unit degree temperature per watt
For an SCR the average & rms values of current are I/4 & I/2 respectively. Calculate the average on-state current rating (ITAV). Take maximum RMS on-state current = 35 A.
Answer: c Explanation: Form factor = RMS/Average vaules of current Therefore, FF = 2 I TAV = 35/2 = 17.5.
Answer: c
See lessExplanation: Form factor = RMS/Average vaules of current
Therefore, FF = 2
I
TAV = 35/2 = 17.5.
An SCR has half cycle surge current rating of 3000 A for 50 Hz. Calculate its one-cycle surge current rating
Answer: b Explanation: By equating the energies involved in one cycle & subcycle I 2 .T = Isb2 .t Isb = 3000 A T = 1/50 t = T/2.
Answer: b
See lessExplanation: By equating the energies involved in one cycle & subcycle
I
2
.T = Isb2
.t
Isb = 3000 A
T = 1/50
t = T/2.
Which among the following anode current waveforms will have the minimum junction temperature?
Answer: b Explanation: N % DC is nothing but a wave with n % duty cycle. Lower the Duty cycle lesser is the current flowing & lesser is the temperature dissipation.
Answer: b
See lessExplanation: N % DC is nothing but a wave with n % duty cycle. Lower the Duty cycle
lesser is the current flowing & lesser is the temperature dissipation.