Network Feedback after EN-61000-3-2 Under Control
Virtually every industrial device requires a rectifier on the network’s side. Modern drive solutions are based on an inverter. In both cases, the EN 61000-3-2 network feedback standard applies to rated currents of up to 16 A per conductor. It prescribes limits for harmonic currents. With conventional diode or thyristor rectifiers, however, the standard can hardly be complied with. In addition to this, the corresponding passive filters are bulky and expensive. For this reason, solutions with electronic PFC (Power Factor Corrector) are used in most cases today. They ensure that the currents on the network’s side are sinusoidal and in phase with the voltage.
Stettbacher Signal Processing AG (SSP) offers application-specific intelligent 1- and 3-phase rectifiers and inverters with PFC up to around 10 kW. The devices are designed for string voltages between around 85 V and 230 V, which covers virtually all public grids in the world. At the output, the rectifiers, which are designed as buck converters and fit into a small or medium-sized shoebox depending on the power rating, supply a DC voltage of 0 to 400 V (with 230 V AC at the input) that can be adjusted during operation. This can be used to operate standard PM synchronous motors, for example. The variable bus voltage improves the control response to load changes. The efficiency of the circuits is excellent >95 %, so that hardly any significant waste heat occurs.
The picture shows the spectrum of the line current of an SSP rectifier at 1 kW power and 97 % efficiency. The 7th harmonic dominates. However, it is attenuated by 34 dB compared to the mains frequency. So, it falls below the standard for class A by a factor of more than 20.
© SSP. All rights reserved.
built by Andy