George You might try Cranage EMC technology Ltd in the UK Tel: +44 1494 444255 [email protected] www.cranage.co.uk Regards Alan E Hutley [email protected] www.emc-journal.co.uk -----Original Message----- From: Georg M. Dancau <[email protected]> To: emc-pstc discussion group <[email protected]> List-Post: [email protected] Date: Wednesday, March 11, 1998 03:42 Subject: Shielded contactors / Three phase
>Hi folks. > >I need some help in the following issue: > >We use in our machines adjustable speed power drive systems. They are >synthesizing >a three phase sine wave by PWM. They have a very high disturbance >potential, >especially from the cable to the motor. If this cable is shielded and >the >shield is correctly bonded at both ends, the disturbances induced in >other are >usually below the limits. It is very important to bond the shield >correctly. > >Now the problem: >Some times it is necessary (for safety reasons) to galvanically >disconnect the motor >from the drive system. At that point disturbances are created because: >- an impedance is added to the shield path (return path for HF), thus >dramatically reducing the effectiveness of the shield. >- the inner conductor build a radiating loop >- disturbances are coupled into the coil of the contactor an thus spread >into the machine >- disturbances are coupled in the wires to the auxiliary contacts >- disturbances are coupled in other wires in the neighborhood > >A possible solution would be a contactor having the power contacts in a >shielded enclosure and the coil and the auxiliary contacts outside the >shielded enclosure. > >[ see http://ourworld.compuserve.com/homepages/dancau/contacto.htm for >image] > >DOES ANYBODY KNOW A SUPPLIER FOR SUCH CONTACTORS ? > >Another possible solution would be to place the contactor in a shielded >enclosure, bond the shield to the enclosure and to filter all wires >going in and out (to the coil and to the auxiliary contacts). My >experience shows that the requirements to the filter for the coil are >very high. and thus expensive. > >Any comments on this issue are welcome. > >Thanks in advance > > >George > > > >-- >************************************************************** >* Dr. Georg M. Dancau * HAUNI MASCHINENBAU AG * >* [email protected] * Manager EMC Lab * >* TEL: +49 40 7250 2102 * Kampchaussee 8..32 * >* FAX: +49 40 7250 3801 * 21027 Hamburg, Germany * >************************************************************** >* home: Tel: +49 4122 99451 * Hauptstr. 60a * >* Fax: +49 4122 99454 * 25492 Heist, Germany * >************************************************************** > > > >
