What is commutation theory?

What is commutation theory?

In the usual theory of commutation it is considered that, when the current in a coil is commutated or reversed, the local magnetic flux due to the current reverses also, and in so doing sets up an e.m.f. in the coil which opposes the reversal.

What are the different types of commutation?

Three types of commutation are identified: i) Voltage commutation, ii) Current commutation and iii) Load commutation.

What are the purposes of a commutation circuit?

The purpose of the commutation cell is to “chop” DC power into square wave alternating current. This is done so that an inductor and a capacitor can be used in an LC circuit to change the voltage. This is in theory a lossless process, and in practice efficiencies above 80-90% are routinely achieved.

What are the commutation methods of SCR?

Thyristor Commutation Techniques

• Natural Commutation.
• Forced Commutation. Class A: Self or Load Commutation. Class B: Resonant-Pulse Commutation. Class C: Complementary Commutation. Class D: Impulse Commutation. Class E: External Pulse Commutation.

What is commutation period?

The commutation in DC machine or more specifically commutation in DC generator is the process in which generated alternating current in the armature winding of a dc machine is converted into direct current after going through the commutator and the stationary brushes. It is called commutation period.

What are the types of commutation according to class?

There are mainly two types of SCR commutation techniques: Natural Commutation and Forced Commutation.

What is the commutation formula?

Formula for working out Commuted Value of pension = Amount of pension to be commuted X 12 X purchase value for age next birth day….Model Calculation: Commutation.

What is interest rate on commutation?

Permissible commutation was also raised from one third to 40% of the basic pay w.e.f. 1.1. 96. The Commutation Factor (CF) came down to 9.81 from 10.46. The rate of interest was 4.75% p.a. Those who superannuated between 1.1.

Why current commutation is best?

The capacitor always remains charged with the correct polarity. Commutation is reliable as load current is less than the peak commutation current ICP. The auxiliary thyristor TA is naturally commutated as its current passes through zero value.

Which circuit works on the principle of current commutation?

The working principle of current commutated chopper is based on current commutation technique of thyristor. The energy required for commutation comes from the charged capacitor C. This capacitor is first charged to source voltage Vs by charging resistor RC.

What is a Class D commutation circuit?

Class D commutation is also called as Impulse Commutation or Voltage Commutation. As Class C, Class D commutation circuit also consists of two Thyristor T1 and T2 and they are named as main and auxiliary respectively. Here, diode, inductor, and auxiliary Thyristor form the commutation circuit.

What is natural commutation in a circuit?

Natural Commutation occurs only in AC circuits, and it is named so because it doesn’t require any external circuit. When a positive cycle reaches to zero and the anode current is zero, immediately a reverse voltage (negative cycle) is applied across the Thyristor which causes the Thyristor to turn OFF.

What are the different methods of forced commutation?

The forced commutation can be classified into different methods as follows: Class A: Self commutated by a resonating load. Class B: Self commutated by an LC circuit. Class C: Cor L-C switched by another load carrying SCR. Class D: C or L-C switched by an auxiliary SCR. Class E: An external pulse source for commutation.

What is Class C complementary commutation?

Class C commutation is also called as Complementary Commutation. As you can see the circuit below, there are two Thyristor in parallel, one is main and another is auxiliary. Initially, both the Thyristor are in OFF condition and the voltage across capacitor is also zero.