2024-07-23 22:00:00
In industry, many processes generate disturbances on the distribution networks of large production sites. These networks must meet well-defined standards to guarantee the proper functioning of the connected devices and the comfort of users. The networks are disturbed, either because of the process itself, or because of the static actuators that supply said processes.
A distinction must be made between the different polluters depending on the power supply mode: some processes are powered directly by the network, others require converters… Rolling mills, large welding machines and certain arc furnaces, known as direct current, are not connected directly to the network, AC/DC converters, with thyristors or IGBTs provide the interface. The advantage of these converters is current control, which is all the more effective as the actuator is fast: for example, a three-phase Graëtz bridge, with thyristors, can respond in one arch, or 3.3 ms on a 50 Hz network. A Graëtz bridge is called a direct converter, it is with the natural switching of the thyristors that we go from the network to direct voltage. So-called indirect converters comprise a Graëtz type network converter, a storage element, generally a capacitor, and an output converter with components that can be blocked by the GTO or IGBT type control capable of operating with switching frequencies much higher than that of the network, so for the load the response time is much shorter than that of a simple Graëtz bridge with thyristors.
This is how, for about ten years, processes with a power of less than 10 MW have been powered by indirect IGBT converters, this is particularly the case for large rolling mills, bloomings. When direct thyristor converters were used to power them, due to variations in reactive power, bloomings disrupted the networks, but the disturbances were balanced over the three phases, hence the use of fairly simple statocompensators or SVCs. With AC arc furnaces whose power can exceed 100 MW, there are single-phase short-circuits in the melting phase, the effects of which on the network are much more difficult to limit. At this power level, it is not yet realistic to consider power supplies with indirect converters, but there are furnaces, called direct current, powered by direct thyristor converters, based on Graëtz bridges with some topological developments intended to reduce the variations in reactive power which are mainly responsible for disturbances on the networks. That said, especially at the start of melting, even with direct current furnaces, arc breaks are frequent, and because of the direct conversion, they are perceived by the networks…
The purpose of this article is to assess the disturbances caused by arc furnaces on distribution networks and to consider correction devices.
1722163266
#Flicker #generated #arc #furnaces #Complete #file
