EMC and Bonding

EMC & Bonding in the Cubicle: Quick Guide

We all know about requirements for ground/earth bonded connections for electrical safety.  However, bonding to ensure EMC noise immunity is also an essential requirement in a drive cubicle.  The topic can seem complex but here are some essential basics:

A continuous bond of earthed metal is required from all the DELTA transistor modules to the controller – this is usually achieved by a wide steel plate that provides a low inductance path between modules and to the controller.  The use of small cables and braids has generally been found to be ineffective when compared to a wide plate.

Also bond the DELTA power modules together using the bonding plate supplied with the DELTA modules to form a single metal highway across the front of the DELTAs.  This arrangement forms a ground plane (low resistive and low inductive path) against which the control ribbon cables must be run. (Not generally needed to be extended to the rectifier modules).

Make sure the delta mounting frame is unpainted and makes a low impedance bond to the cubicle.

Remember too that the screened control ribbon cables also provide a low inductance path but must have their screens bonded to the metalwork using the ribbon cable clamps to remove the noise from the screens.