MURRELEKTRONIK, represented in Australia by Sick , has released the MEF mains suppression filters. They provide reduced emitted interference and improved immunity from internal and external interference on mains and power-supply cable. EMC filters are suitable for protecting machines or systems with frequency converters or pulsed power supply.
Mains suppression filters combined with EMC-oriented installation of switch cabinets and machines help implement the protection specified in EU Directive 89/336/EEC as well as machine guideline 98/37/EG. This increases both the safety and the availability of machines. The costs of loss of production and rectification of faults that stem from EMC problems are significantly higher than the purchase price of a filter.
The three-phase mains filters have a current range of up to 180A and a compact book format for high damping characteristics. Optimal use of space close to the feed or the source of interference is achieved through end mountings. Operating voltages of up to 600V ac allow them to be used worldwide.
The range includes snap-on one and three-phase mains filters up to 20A. Filters with four-wire technology (three phases + N) are suitable as input filters and are used in cases where 230V consumers are also present. The low consumption means that there is little pre-loading of FI protection switches. The fault current protection switch is not triggered any sooner than necessary.
The integrated snap-on base allows the devices to be quickly attached to support rails next to input terminal blocks. The screw terminals are easy to connect and are touch protected. Unlike low-cost solutions with a plug connector, there is no risk of electrocution if the load side is unintentionally disconnected. The PE terminal is coloured green and yellow to prevent erroneous connections.
In residential areas or mixed residential/industrial areas the company recommends two-stage mains filters with increased damping to conform to the Class B interference emission limits defined in EN 55022 and 55011.
Murrelektronik supplies two variants of the two-stage filters which offer high energy absorption and wide-band damping behavior up to 30Hz. The first line is designed to suppress the essentially symmetrical interference (differential mode) that occurs in conventional motor drives and between the lines in the low frequency range because of inductivity without interference suppression.
The product line that is protected from asymmetrical interference (common mode) is designed for the higher-frequency range with frequency inverters and switch mode PSUs. Mixed interference usually occurs, meaning that both types of filter can be used. For optimum filter adaptation individual measurement on site or in the EMC test laboratory is recommended.
Cable-bound interference in mains ac voltage is suppressed by the low-pass filter-like functionality. This means that the filters can also be used for 24V direct voltage supplies.
The one or two-stage filters provide excellent damping properties, low consumption, with a compact and lightweight design. The robust metal housing creates a low-impedance connection to the mounting plate. The PE connection is made using screw thread bolts. The mounting facility on the front makes optimum use of space at the power supply (collective interference suppression) or next to the source of interference (individual interference suppression).