How do load commutated inverters work?

Load Commutated Inverter (LCI) is a system with an input thyristor bridge and an output thyristor bridge. The output bridge operates at low speed by turning on a set of 2 thyristors to pass the DC current into the generator’s stator to cause it to rotate.

What does line-commutated mean?

The term line-commutated indicates that the conversion process relies on the line voltage of the AC system to which the converter is connected in order to effect the commutation from one switching device to its neighbour.

What is a forced commutated inverter?

An analysis of the circuit is undertaken to provide both the current waveforms and the regulation characteristic, which are compared with those of a conventional rectifier. …

Why can line-commutated inverters not be used in stand alone systems?

Line-commutated inverters are not suitable for use in stand-alone systems because AC voltage is required to turn off the thyristors, although self-commutated inverters can operate without AC grid voltage.

What is load commutated?

Load commutation of SCR is a forced commutation technique in which SCR is forced to turn off. Turning off an SCR essentially requires its anode current to fall below holding current and a reversed biased voltage must be present across SCR for sufficient time so that SCR may regain its blocking state.

What is commutation technique?

Commutation is defined as the process of turning-off a thyristos. – Turn-off of a thyristor means, bringing the device. from forward-conduction mode to forwarda blocking mode. – Turn-off process of thyristor requires. @ Anode current to be reduced below holding current.

What are the drawbacks of forced commutated chopper?

One disadvantage of this type of commutation is that the load regulation is poor. Figure 11.58(d) shows an alternative configuration of the series commutation circuit. Here the circuit oscillation will cause C to charge to a voltage nearly twice the supply voltage (i.e., 2 Vdc).

What is forced commutated?

Forced Commutation In such circuits, forward current must be forced to zero with an external circuit (known as Commutating Circuit) to commutate the SCR. Hence the name, Forced Commutation. This commutating circuit consist of components like inductors and capacitors and they are called Commutating Components.

What are the disadvantages of load commutated chopper?

Disadvantages of load commutated chopper

• For high power applications, efficiency becomes very low because of high switching losses at high operating frequencies.
• Freewheeling diode is subjected to twice the supply voltage.
• Peak load voltage is equal to twice the supply voltage.

What happens if the field winding of the synchronous motor is short circuited?

In the case of an induction motor, the field winding is permanently short-circuited by end rings. In a Synchronous motor, the rotor winding is supplied with DC excitation. Therefore if we short circuit the field winding of a synchronous motor then it will behave as an induction motor.