What is overlap Why does it occur in converter?

What is overlap Why does it occur in converter?

The two thyristors from the same group in effect constitute a short circuit of two phases via the source impedance; this is called overlap. No surge of current is observed but the fact that two phases are shorted reduces the voltage available to the load. More importantly ‘notches’ distort the line voltage.

What happens when commutation overlap occurs in three phase fully controlled converters?

It takes place over an overlap period of “μ1” instead. During the overlap period three thyristors instead of two conducts. Current in the outgoing thyristor gradually decreases to zero while the incoming thyristor current increases and equals the total load current at the end of the overlap period.

What is overlap in circuit?

An overlap in railway signalling is the length of track beyond a stop signal that is proved to be clear of vehicles in the controls of the previous signal, as a safety margin.

How do you find the angle of commutation?

U d = 3 2 2 π U ( cos α + cos ( α + u ) ) = 3 2 U π cos α − 3 ω L π , where U is the phase–phase ac voltage, α the delay angle, u the commutation angle, and ω L is the transformer reactance per phase. Output voltages with different values of delay angle α, neglecting commutation angle, are shown in Fig.

What is meant by commutation overlap?

Commutation is the process when conduction switches from one supply phase to another. Commutation overlap occurs when there is inductance in the supply circuit of a diode (or thyristor) rectifier. Rather, the diode will only turn off once the current falls to zero. …

What is commutation angle?

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 meant by 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.

When does commutation overlap occur in a diode rectifier?

Commutation overlap occurs when there is inductance in the supply circuit of a diode (or thyristor) rectifier. It can be seen by adding a supply inductance to the 3-phase supply in the diode rectifier simulation .

What do you need to know about commutation angle?

Commutation requires knowledge of rotor position with regard to the magnetic poles of the motor. For resolvers, which normally provide an absolute position within one revolution of the motor, this problem is most often solved by mechanically aligning the resolver to the magnetic poles of the motor.

How many diodes conduct at the same commutation angle?

Assuming we have no source inductance and other ideal conditions, diodes from 1 to 6 are conducting at following angles (of course we need to add some load): As we can see, each of the diodes conduct exactly 120º per cycle. Also, conduction of diodes 1,3,5 and 4,6,2 does not overlap.

How is the angle of conduction and overlapping angle affected?

Subsequently, the conduction angles start overlapping. For example, diode 1 conducts from 20º to 160º and diode 3 conducts from 140º to 280º. Diodes 1 and 3 are overlapping for 20º. My question is – how is the angle of conduction and overlapping angle affected?