Define commutation. Give the types of commutation.

Define commutation. Give the types of commutation.
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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) External pulse commutation

OR

i) Class A: load commutation (Self-commutated by resonating the load) ii) Class B: Resonant pulse commutation iii) Class C: Complementary commutation iv) Class D: Auxiliary commutation v) Class E: External pulse commutation vi) Class F: AC line commutation
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Related questions

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

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.

Draw circuit diagram of Class B commutation.

Description : Draw circuit diagram of Class B commutation.

Last Answer : Class B: Resonant Pulse Commutation:

Differentiate between Natural and Forced commutation

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

Class D commutation

Description : Class D commutation

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.

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

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.

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

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

Last Answer : voltage commutation

Class A Load Commutation

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. 

Draw a neat circuit diagram of class F commutation

Description : Draw a neat circuit diagram of class F commutation

Last Answer : class F commutation

In a 3-phase converter circuit during commutation when one SCR in one phase is turned on to turn-off an SCR

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

Satisfactory commutation of D.C. machines requires?

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.

What is mean by forced commutation of thyristor?

Last Answer : By using some circuit the forward DC current of thyristor is forced to zero is called forced commutation.

What is mean by natural commutation of thyristor?

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.

what is thyristor commutation?

Last Answer : Thyristor commutation means turning off thyristor.

Natural commutation means:

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)

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

Which of the following is also called as voltage 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

What are the different types of chopper with respect to commutation process?

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.

What are the types of commutation with respect to commutation process?

Description : What are the types of commutation with respect to commutation process?

Last Answer : Voltage commutated chopper Current commutated chopper Load commutated chopper

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

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

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 : 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

Last Answer : Answer: D

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.

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

How is the inverter circuit classified based on commutation circuitry?

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.

What is meant by load commutation?

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.

What is meant by current commutation?

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.

What is meant by voltage commutation?

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.

What is commutation angle or overlap angle?

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.

What is forced commutation?

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.

What is natural 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.

What is meant by 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.

What is commutation?

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.

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

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

Explain the process of commutation in a dc machine. Explain what are inter-poles and why they are required in a dc machine.

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.

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 improved with reduction in harmonics. (C) The inequality of air flux on the top and bottom halves of armature is removed. (D) A counter e.m.f. is induced in the coil undergoing 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.

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

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

Natural commutation can be used in ,

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

Define: i) Firing angle ii) Conduction angle

Description : Define: i) Firing angle ii) Conduction angle

Last Answer : i) Firing angle: The firing angle of a thyristor is defined as the angle between the zero crossing of the applied voltage and the instant at which the thyristor is triggered or fired. It is a ... off. It is a measure of the duration for which the thyristor conducts current during each AC cycle.

Define transfer time and back up time of UPS.

Description : Define transfer time and back up time of UPS.

Last Answer : Transfer time of UPS: The transfer time, sometimes also called switchover time, is the amount of time the UPS will take to switch from utility to battery supply during a mains failure, or from battery to ... is the amount of time for which the UPS will supply the power to load during mains failure.

Define triggering. List the type of triggering.

Description : Define triggering. List the type of triggering.

Last Answer : Triggering: Triggering means turning-ON of a device from its OFF-state.  Types of Triggering: 1) Forward voltage triggering 2) Thermal triggering (Temperature triggering) 3) Radiation triggering (Light triggering) ... (i) D.C. Gate triggering (ii) A.C. Gate triggering (iii) Pulse Gate triggering

what is rectifier and its types?

Last Answer : rectifier is a device which converts AC voltage to pulsating DC voltage using one or more diode diode conducts only in unit direction that is forward bias condition practically it does not conduct ... types one is with using two diodes and Centre tap Transformer and another is bridge wave rectifier

Give the operation of single phase full wave bridge controlled converter with RL load with a neat diagram. Also draw its waveform.

Description : Give the operation of single phase full wave bridge controlled converter with RL load with a neat diagram. Also draw its waveform.

Last Answer : Single phase fully control bridge converter with RL load: 1. During positive half cycle of input voltage, T1 and T2 are forward biased and during negative half cycle, T3 and T4 are forward biased. Therefore, T1-T2 ... cycle till the firing of next pair of SCRs as shown in the waveform.

Give the effect of source impedance on converter operation.

Description : Give the effect of source impedance on converter operation.

Last Answer : Effect of source impedance on converter operation: For single-phase fully controlled bridge converter, the SCRs are triggered in pairs alternately. During positive half-cycle of input, SCRs T1 and T2 are triggered ... increases and as a consequence, the output dc voltage decreases. 

Draw a neat diagram of 1Ф half wave controlled converter with RL load. Give its operation.

Description : Draw a neat diagram of 1Ф half wave controlled converter with RL load. Give its operation.

Last Answer : Single phase fully controlled half wave converter:  The circuit diagram of single-phase half-wave controlled rectifier with RL load and without freewheeling diode is shown in Fig. (a). The SCR T is ... , when again pulse is applied, the SCR is turned on & the above cycle is repeated. 

Give the circuit analysis of current source inverter with resistive load.

Description : Give the circuit analysis of current source inverter with resistive load. What are the main difference between voltage source inverter and current source inverter?

Last Answer : Current source inverter (CSI): In current source inverter, the output current is independent of load. The input current of current source inverter is constant. Current source converter converts DC input current to ... are connected in parallel. In CSI diodes are connected in series.