Low leakage current 3-phase filter

Paul Boughton

SCHURTER has expanded its range of FMBC NEO 3-phase filters with a low leakage current series for applications where no high leakage currents are allowed. The new FMBC LL series of filters has been designed for rated currents between 7 and 180A. It is suitable for leakage current-critical industrial applications such as drive technology.

More and more of today's electrical installations in industry are being fitted with residual current devices (RCD) to ensure efficient personal protection. This is also required in certain countries for three-phase systems, for example for plug-in systems up to 32A.

The RCD limits the current to earth to a maximum of 30mA. This poses a particular problem in drive technology since the frequency inverters that control the engine generate considerable leakage current. Long motor cables further aggravate the problem since they increase the capacity to earth and hence the currents to earth too. The new series of FMBC LL filters helps reduce the leakage currents and permits compliance with common EMC standards as an efficient input filter.

The compact FMBC LL 3-phase filters have been designed for currents from 7A to 180A at an ambient temperature of 50°C. They have UL approvals for ambient temperatures of +50°C as well as +40°C with a higher rated current and are approved for rated voltages of 520VAC. This means that they can be used in all high-power systems, for example in machines in an industrial environment. Despite the high output, they are still compact and lightweight in design.

The FMBC LL is fitted with a screw connection as standard. Other types of connection (wires or copper bars) are possible in request, as are customised modifications to the circuit or housing. SCHURTER also offers its own EMC measuring service for an optimum adjustment to the inverter. The most efficient filter solution for the system can therefore be developed.

Technical features include:

* Rated current: 7 A to 180A;

* Leakage current 7–55A: <5mA, leakage current  75–180A: <20mA;

* Screw connections;

* cURus approval: E72928.