Natural commutation means: reducing the current to zero and allowing time to recover thyristor junctions
Description : Differentiate between Natural and Forced commutation
Last 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
Description : For a class D commutation, answer the following: i) Explain the operation with circuit diagram. ii) Interpret with waveforms.
Last 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.
Last Answer : Class B: Resonant Pulse Commutation:
Description : Class D commutation
Description : Explain auxiliary commutation with a neat diagram. Also draw its waveform.
Last 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.
Last 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
Description : Which of the following is also called as voltage commutation? (a) CLASS A (b) CLASS B (c) CLASS C (d) CLASS D
Last Answer : Which of the following is also called as voltage commutation? (a) CLASS A (b) CLASS B (c) CLASS C (d) CLASS D
Description : In a thyristor D.C. chopper, which type of commutation results in best performance ?
Last Answer : voltage commutation
Description : What is natural commutation?
Last Answer : The process of the current flowing through the thyristor goes through a natural zero and enable the thyristor to turn off is called as natural commutation.
Last Answer : Natural commutation can be used in , AC circuits only.
Last Answer : 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 ... connected to positive and anode terminal get connected to negative, this turns off the thyristor.
Description : Which of the listed colors properly describes a DC motor commutator when correct commutation is taking place? A. Shiny blue B. Burnished green C. Brick red D. Chocolate brown
Last Answer : Answer: D
Description : Brush sparking during commutation may be caused by ________. A. eddy currents in the armature core B. laminations in the generator field pieces C. induced current opposite to coil inductance D. coil inductance discharge occurring at commutation
Description : What is the function of the interpoles installed in DC motors? A. To provide greater torque by strengthening the main field. B. To provide sparkless commutation without having to shift the brushes. C. To limit the production of counter-electromotive force. D. To limit the starting surge current.
Last Answer : Answer: B
Description : How is the inverter circuit classified based on commutation circuitry?
Last Answer : a. Line commutated inverters. b. Load commutated inverters. c. Self commutated inverters. d. Forced commutated inverters.
Description : What is meant by load commutation?
Last Answer : In this process, the load current flowing through the thyristor either becomes zero or is transferred to another device from the conducting thyristor.
Description : What is meant by current commutation?
Last Answer : In this process, a current pulse is made to flow in the reverse direction through the conducting thyristor and when the net thyristor current becomes zero, it is turned off.
Description : What is meant by voltage commutation?
Last Answer : In this process, a charged capacitor momentarily reverse biases the conducting thyristor and turn it off.
Description : What are the different types of chopper with respect to commutation process?
Last Answer : a. Voltage commutated chopper. b. Current commutated chopper. c. Load commutated chopper.
Description : What is commutation angle or overlap angle?
Last Answer : The commutation period when outgoing and incoming thyristors are conducting is known as overlap period. The angular period, when both devices share conduction is known as the commutation angle or overlap angle.
Description : What are the types of commutation with respect to commutation process?
Last Answer : Voltage commutated chopper Current commutated chopper Load commutated chopper
Description : What is forced commutation?
Last Answer : The process of the current flowing through the thyristor is forced to become zero by external circuitry is called as forced commutation.
Description : What is meant by commutation?
Last Answer : The process of changing the direction of current flow in a particular path of the circuit. It is used to turn off the SCR.
Description : What is commutation?
Last Answer : Usually the width of the brush is equal to the two segments of the commutator. Whenever a brush contacts two or more commutator segments, the connected to those segments are short- ... the winding. The remedies for rough commutation are resistance commutation method and emf commutation method.
Description : The reduction in the amount on account of commutation shall become operative within -- ------- months after issue of letter by the competent authority a. Five b. Two c. Three
Last Answer : c. Three
Description : Explain the process of commutation in a dc machine. Explain what are inter-poles and why they are required in a dc machine.
Last Answer : Commutation: It is phenomenon when an armature coil moves under the influence of one pole- pair; it carries constant current in one direction. As the coil moves into the influence of the ... region of the main poles and therefore influence the armature coils only when these undergo commutation.
Description : The introduction of interpoles in between the main pole improves the performance of d.c. machines, because (A) The interpole produces additional flux to augment the developed torque. (B) The flux waveform is ... armature is removed. (D) A counter e.m.f. is induced in the coil undergoing commutation.
Last Answer : Ans: D Counter e.m.f is produced, it neutralizes the reactive emf.
Description : Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ? (a) Increased I R losses (b) Increased core losses (c) Poor commutation (d) Change in motor parameters (e) All of the above
Last Answer : (e) All of the above
Description : Class A Load Commutation
Last 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 : Draw a neat circuit diagram of class F commutation
Last Answer : class F commutation
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
Last 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
Last 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.
Last Answer : By using some circuit the forward DC current of thyristor is forced to zero is called forced commutation.
Last Answer : Thyristor commutation means turning off thyristor.