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Natural commutation is also called as line Communication. The turning off of thyristor due to AC supply is called natural commutation or line commutation. If the thyristor is connected to AC supply then it reverse the polarities means the cathode terminal get connected to positive and anode terminal get connected to negative, this turns off the thyristor.
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Answer : By using some circuit the forward DC current of thyristor is forced to zero is called forced commutation.

Description : Differentiate between Natural and Forced commutation

Answer : Natural commutation Forced commutation Source is AC Source is DC External commutating componants are not required  External commutating componants are required SCR turns off ... in controlled rectifiers, AC voltage controllers etc.  Used in choppers & inverters etc

Answer : Thyristor commutation means turning off thyristor.

Description : In a thyristor D.C. chopper, which type of commutation results in best performance ?

Answer : voltage commutation

Description : Class A Load Commutation

Answer : Class A: Load Commutation: The class A or load commutation (also called self-commutation or resonant commutation) is employed in thyristor circuits supplied from DC source. The commutating components include ... biased. Thus the zero-current and reverse-bias cause the thyristor to turn-off. 

Description : In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR in another phase, results in (A) voltage notching (B) harmonic distortion (C) voltage sag (D) voltage swell

Answer : In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR in another phase, results in voltage notching

Description : An accelerometer has input range of 0 to 10g, natural frequency 30 Hz and mass 0.001 kg. The range of the secondary displacement transducer in mm required to cover the input range is (A) 0 to 2.76 (B) 0 to 9.81 (C) 0 to 11.20 (D) 0 to 52.10

Answer : An accelerometer has input range of 0 to 10g, natural frequency 30 Hz and mass 0.001 kg. The range of the secondary displacement transducer in mm required to cover the input range is 0 to 2.76

Description : For a class D commutation, answer the following: i) Explain the operation with circuit diagram. ii) Interpret with waveforms.

Answer : Class D commutation: This is also called as auxiliary commutation because it uses an auxiliary SCR to switch the charged capacitor across conducting SCR to turn it off. In this scheme, the main ... make SCR1 forward biased and keep ready for next triggering. The above cyclic process is repeated.

Description : Draw circuit diagram of Class B commutation.

Answer : Class B: Resonant Pulse Commutation:

Description : Class D commutation

Answer : Class D commutation: This is also called as auxiliary commutation because it uses an auxiliary SCR to switch the charged capacitor across conducting SCR to turn it off. In this scheme, the main ... make SCR1 forward biased and keep ready for next triggering. The above cyclic process is repeated.

Description : Draw a neat circuit diagram of class F commutation

Answer : class F commutation

Description : Explain auxiliary commutation with a neat diagram. Also draw its waveform.

Answer : Auxiliary Commutation At start, the Ta is triggered and turned on to carry the load current. Due to the resonant circuit R-L-C, the current initially rises, attains peak and then falls to ... , the firing of auxiliary SCR commutates the main SCR, hence name is auxiliary commutation.

Description : Define commutation. Give the types of commutation.

Answer : Commutation: The process of turning-off a conducting thyristor is called commutation . Types of Commutation: i) Line commutation (Natural commutation) ii) Load commutation iii) Forced commutation iv) ... Auxiliary commutation v) Class E: External pulse commutation vi) Class F: AC line commutation

Answer : Satisfactory commutation of D.C. machines requires brushes should be of proper grade and size, brushes should smoothly run in the holders, smooth, concentric commutator properly undercut.

Answer : No we cannot turn off normal thyristor using Gate.

Answer : Thyristor conducts when the anode voltage is greater than cathode and when the current provided to Gate.

Description : How to choose high quality and natural dairy products?

Answer : Dairy products have always been the basis of nutrition, and this is quite justified: after all, they contain only natural substances that contribute to normal digestion. However, in an effort to reduce ... kilogram. Real sour cream will only be called sour cream, and butter will be called butter.

Description : Define natural, mechanical, forced and induced draught systems.

Answer : Natural draught system: - When the fuel is burnt (combustion) in the furnace due to natural circulation of air, the draught is called natural draught. Mechanical draught system: -  In a mechanical ... combustion. OR If fan/blower is placed after the furnace then it is called as induced draught

Answer : Natural air cooling is generally restricted for transformers up to 1.5 MVA .

Description : What is meant by firing angle of thyristor?

Answer : The point at which SCR is triggered is known as firings angle of thyristor.

Description : Thyristor can be protected from over voltages by using

Answer : Thyristor can be protected from over voltages by using Voltage clamping device

Description : thyristor can be turned off by?

Answer : Thyristor can be turned off by making anode potential equal to cathode potential or by making anode potential less than cathode potential.

Description : What is a phase control thyristor?

Description : What is thyristor family?

Description : What is the use of a thyristor in a circuit?

Description : What is a reverse conducting thyristor?

Description : What is the function of a thyristor?

Description : What is the application of thyristor?

Description : what are the disadvantages of thyristor?

Answer : Disadvantages of thyristor The silicon controlled rectifier (SCR) is unidirectional devices, so it can control power only in DC power during positive half cycle of AC supply. Thus only DC power is ... cycle. It cannot be used at higher frequencies. The gate current cannot be negative

Description : Draw the structural diagram of GTO. Explain briefly the switching behavior of GTO with the help of appropriate voltage and current waveform.

Answer : Gate Turn Off Thyristor (GTO) Conventional Thyristor can be turned on with gate terminal but can not turn off from gate terminal. But in case of Gate Turn Off Thyristor (GTO), we can turn it on and off ... subdivided as storage period (Ts), fall period (Tp) and tail period (Tt).

Description : Describe the working principle of Thyristor operated dimmer with the help of circuit diagram.

Answer : Thyristor operated dimmer: A popular thyristor operated dimmer circuit employ TRIAC-DIAC phase control for low AC power control. During each half-cycle, the capacitor charges through (R1+VR1). When the ... time constant {C (R1+VR1)}. Thus by reducing VR1 the lamp brightness can be increased.

Description : Leakage current flows through the thyristor in

Answer : Leakage current flows through the thyristor in Forward blocking mode and Reverse blocking mode.

Description : Why thyristor are not preferred for inverter?

Description : Why SCR is called as thyristor?

Description : Is a SCR a thyristor?

Answer : Yes, SCR is a thyristor. Thyristor is the family and SCR is the member of that family but SCR is universally known as thyristor.

Description : How is a thyristor used to convert AC to DC?

Answer : Yes ,it is one of the main advantage using thristors as a  switch in DC  circuit ,it has a high current gain

Description : Explain thyristor gate drive circuit.

Answer : Thyristor Gate Drive Circuit: The thyristor can be turned on by pulse voltage signal at gate terminal and it does not require continuous drive signal like the transistor. The gate ... circuit provide required minimum gate voltage and gate current then the thyristor conducts properly.

Description : parallel operation of MOSFET can be done more easily as compared to thyristor. why?

Answer : Parallel operation of MOSFET can be done more easily as compared to thyristor because the resistance of MOSFET is increases with increase in temperature. MOSFET have the positive temperature coefficient. In ... the parallel operation of MOSFET can be done more easily as compared to the thyristor.

Description : write short notes on thyristor CSI .

Answer : Current-source inverter (CSI) is an inverter with a DC current input. Current source inverters are most commonly used in very high power AC motor drives.

Answer : Thyristor have three terminals anode, cathode and Gate.

Answer : Thyristor can only be turned on by small gate pulse but it cannot be turn off by using gate hence thyristor is called semi controlled device.

Answer : Thyristor can be turn on by positive gate pulse and the current will continue to flow through the device even when the gate voltage is low hence thyristor is called latching device.

Description : Thyristor Switched Capacitor (TSC)

Answer : Thyristor Switched Capacitor (TSC)  TSC is a static compensator. TSC is use for compensating reactive power. Compensation is required for voltage regulation, increasing stability, ... compensating device like TCS phase angle between voltage and current can be maintain.

Description : what is TCSC?

Answer : Thyristor Controlled Series Capacitor (TCSC)

Description : Thyristor controlled phase angle regulator

Answer : Thyristor controlled phase angle regulator

Description : Natural commutation means: A) reducing the thyristor current to zero B) reducing the thyristor current below “holding current” C) reducing the current to zero and allowing time to recover thyristor junctions D) none of (A), (B) and (C)

Answer : Natural commutation means: reducing the current to zero and allowing time to recover thyristor junctions 

Answer : Natural commutation can be used in , AC circuits only.

Description : What do you mean by active filter? State its advantages over passive filter . Define pass band & stop band with respect to filter.

Answer : Active Filter: Active Filter is formed by using active element along with the passive components.  Advantages of Active filter over Passive filter: High value of pass band gain can be obtained. It is ... pass band.  Stop Band Filter: The frequency range which is attenuated is known as stop band.

Answer : Nanometer is a ametric measure of distance equivalent to one billionth of a meter.

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