Anglia Components

New output filters improve reliability and flexibility in power drive systems

Being a modular system, Sinus Plus can be arranged optimally according to system requirements and application.

As a symmetrical sinusoidal output filter module, the FN 5020 converts the PWM signal of frequency inverter outputs into a smooth sinusoidal curve, in between the phases. This series of filters can be operated autonomously and offers a vast array of advantages. Connected motors are afforded efficient protection from premature ageing or destruction, as the sinusoidal filter keeps dv/dt and over-voltage stress, in addition to magnetic losses inside the motor, within acceptable limits. Furthermore, acoustic motor noise is minimised, a major consideration in air conditioning, ventilation and heating applications, where noise can be amplified and distributed throughout the entire building by means of air ducts and heating pipes.

In many applications, the FN 5020 symmetrical sinusoidal output filter provides a complete solution. However, it may occasionally be necessary to satisfy even tougher requirements, in such applications, the FN 5030 can be additionally employed.

As an asymmetrical sinusoidal output filter, the FN 5030 significantly improves the voltage signal between the phases and earth (asymmetric). It is an add-on module, for use downstream of the FN 5020 module. It incorporates innovative circuitry and, through a connection to the dc-link of the frequency inverter, provides a direct return path for common mode interference currents to their origin inside the drive. As a result, pulsecurrents to earth are virtually completely eliminated and therefore, both interference propagation coming from the shielded motor cable and detrimental bearing currents are eliminated.

By adopting the Sinus Plus output filter concept, the output signal of various frequency inverters is optimised, both symmetrically and asymmetrically, significantly reducing traditional down-time problems. Efficiency, reliability, operational safety and continuity are all greatly enhanced by the new filters. Since the output signal beyond the two filter modules has a quality close to that of the mains supply, traditional considerations such as cable length and cable shielding become insignificant factors, opening up new, flexible deployment possibilities.

Sinus Plus filters are designed to be operated in 500VAC supply grids with current ratings from 25A to 120A and are suitable for switching frequencies from 6kHz to 15kHz. With the ability to handle motor frequencies up to 600Hz, 'Sinus Plus' has taken into account the growing market trend for motors with very high rotational speeds.

For more information on the full range of Schaffner products available from Anglia please call +44 (0)1945 474747 or email info@anglia.com

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This news article was published in April 2002.