Contents
What is a commutation angle?
Definition of “commutation angle” The commutation period between two thyristors on the same side of the bridge is the angle by which one thyristor commutates to the next. / time in electrical degrees from the start to the completion of the commutation process. Also called overlap angle.
What is the commutation angle of a rectifier?
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 commutation and its types?
The process used for turning off a thyristor is called commutation. By the commutation process, the thyristor operating mode is changed from forward conducting mode to forward blocking mode. The commutation techniques of thyristors are classified into two types: Natural Commutation. Forced Commutation.
What are the different types of commutation techniques?
Forced commutation is divided into six categories, which are explained below:
- Class A: Self or Load Commutation.
- Class B: Resonant-Pulse Commutation.
- Class C: Complementary Commutation.
- Class D:
- Class E: External Pulse Commutation.
What is commutation current?
Commutation is the process of switching the field in the armature windings to produce constant torque in one direction, and the commutator is a device connected to the armature, which enables this switching of current.
What is a firing angle?
Firing Angle: The number of degrees from the beginning of the cycle when SCR is switched on is firing angle. Any SCR would start conducting at a particular point on the ac source voltage. The particular point is defined as the firing angle.
What is commutation voltage?
Commutation is the process when conduction switches from one supply phase to another. If there is inductance in the supply circuit, a conducting diode will not switch off as soon as one of the other phase voltages exceeds the existing supply phase voltage.
What are the effects of commutation overlap?
The overlap during commutation reduces the DC output voltage and the angle of extinction γ resulting in failed commutation when αis close to 180°.
What is commutation process?
Commutation in DC machines is the process by which the reversal of current takes place. In DC generator this process is used to convert the induced AC in the conductors to a DC output. In DC motors commutation is used to reverse the directions of DC current before being applied to the coils of the motor.
How many types of commutation are there?
Three types of commutation are identified: i) Voltage commutation, ii) Current commutation and iii) Load commutation. In a voltage commutated thyristor circuit a voltage source is impressed across the SCR to be turned off, mostly by an auxiliary SCR.
What is class F commutation?
The class F commutation is also called as line or natural commutation because the SCR is turned off automatically during negative cycle of alternating supply. This method is used in the line commutator rectifiers, inverters and cyclo – converters. …
What are commutation methods of SCR?
Natural Commutation As the current in the circuit goes through the natural zero, a reverse voltage is applied immediately across the SCR (due to the negative half cycle). These conditions turn OFF the SCR. This method of commutation is also called as Source Commutation or AC Line Commutation or Class F Commutation.