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New EMC filter for regenerative applications

Schaffner has announced the introduction of the FN3840, an EMC filter for use in Active Infeed Converter (AIC) or Active Front End (AFE) applications where energy is fed back to the power grid.

This process is designed to reduce energy costs in larger factories or can be used to reduce losses and excess heat in converters.

When the semiconductors of the converters are switching directly towards the mains power network, they create a high voltage and current ripple - the inclusion of an LCL-filter such as the FN6840 can further reduce this effect and improve power quality.

The FN3840 series of filters provide EMI attenuation based on an innovative filter topology and help to ensure compliance with Class C2 or even C1 limits. Applications include regenerative drives in combination with LCL filters, active infeed converter (AIC), active front end (AFE) variable frequency drives (VFD), three-phase variable speed drives (VSD) and power drive systems (PDS), renewable energy, machine tool and machinery equipment, process automation equipment.

In systems where compliance to EMC regulations at frequencies above 150kHz need to be considered not every EMC-filter can be connected in-line with an LCL-filter. The inductive components of an LCL-filter can resonate with the capacitors of the EMC-filter and vice versa. To overcome those effects and to avoid damage of the drive, a careful design of the EMC-filter circuit is mandatory. The FN3840 has been fully tested and may be combined with a Schaffner FN6840 LCL-filter in an AIC/AFE application.

The FN3840 is fitted with an onboard temperature monitor to provide protection from overheating. The switch will open at the critical temperatures of 180°C, or 150°C for busbar versions. This provides an extra safety layer for machine builders. In the event of an open temperature switch the Active Infeed Converter can react and reduce or switch off power.

The Schaffner FN3840 is supplied in a slim book-style shape allowing convenient and space-saving installation next to inverters, converters or motor drives. Connection is via solid safety connector blocks and versions are available with low leakage current.

The FN3840 filters provide very high saturation performance combined with high EMI performance fulfilling the requirements in IEC/EN 61800-5-1 for electric strength, clearance and creepage, IEC/EN 60204-1 for insulation resistance, electric strength, clearance and creepage, and the requirements in IEC/EN 62477-1.

Neil Tyler

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