What is difference between natural commutation and forced commutation?
As there is no natural zero current in the DC circuit, extra commutation circuit ( which include L and C ) requires in order to turn off the SCR. The forced commutation may be voltage commutation or current commutation.
What are the advantages of forced commutation?
The advantages of this type of commutation are good load regulation and that the voltage across the thyristor is restricted to no more than the supply voltage. If load resistance R is increased, the charging of capacitor C will be slow, making the minimum off-time longer.
What does line commutation mean?
Natural or Line commutation is a Class-F SCR commutation technique in which, a thyristor is turned off due to natural current zero and voltage reversal after every half cycle.
What are the different classes of forced commutation method?
Classification of Forced Commutation Methods
- 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.
- Class F: AC line commutation.
How many types of forced commutation are there?
We already explained about Thyristor and its Triggering Methods in our previous Article. There are mainly two techniques for Thyristor Commutation: Natural and Forced. The Forced commutation technique is further divided into five categories which are Class A, B, C, D, and E.
What is self commutation?
A self-commutated inverter is one in which the means of commutation is included within the inverter itself. This is the case for circuits including electronic power switches with turn-off capability. Thus, a bipolar transistor, GTO thyristor, or power FET inverter is self-commutated.
Where is forced commutation used?
Forced Commutation This kind of commutation is used in AC voltage controller and controlled rectifiers. It is used in inverters and choppers. A thyristor can be simply called a controlled rectifier.
Why forced commutation is used in DC Chopper?
A forced commutation chopper control for regulating speed of a DC series tractive motor limits peak motor current by sensing the voltage across the commutation capacitor during the on-time of the current pulses and gating the commutation SCR on in response to a predetermined magnitude of sensed voltage to thereby …
