Installation
CDHD
18
Servotronix
3.2.3
Electrical Requirements
Grounding
System grounding is essential for proper performance of the drive system. A
ground bus bar may be used as a single point ground for the system. Safety
grounding should be provided to all pieces of the system from a star point.
In addition to the safety grounding, a high frequency ground must be provided
that connects the back panel to the enclosure and to earth ground. The objective
is to provide an extremely low impedance path between the filters, drives, power
supplies, and earth ground.
This high frequency ground is accomplished with the use of a flat braid or copper
bus bar. It is important not to rely on a standard wire for the high frequency
ground. In general, a wire has an inductance of 8 nH per inch, regardless of
diameter. At higher frequencies, this unwanted inductance between grounds
equates to limited filter performance. When connecting high frequency grounds,
use the shortest braid possible.
Bonding
The proper bonding of shielded cables is imperative for minimizing noise
emissions and increasing immunity levels of the drive system. Its effect is to
reduce the impedance between the cable shield and the back panel. Servotronix
recommends that all shielded cables be bonded to the back panel.
The motor and feedback cables should have the shield exposed as close to the
drive as possible. This exposed shield is bonded to the back panel using either
non-insulated metallic cable clamps or cable bonding clamps offered by Phoenix
Contact (and others).
CE Filtering Techniques
The CDHD drive system (bus module, drive, motor) complies with the CE
standards specified in the section Standards Compliance. Proper bonding and
grounding techniques must be applied when incorporating EMC noise filtering
components in order to meet this standard.
Noise currents often occur in two types. The first is conducted emissions that are
passed through ground loops. The quality of the system grounding scheme
inversely determines the noise amplitudes in the lines. These conducted
emissions are of a common-mode nature from line to neutral (or ground). The
second is radiated high-frequency emissions usually capacitively coupled from
line-to-line and are differential in nature.
To properly mount the filters, the enclosure should have an unpainted metallic
surface. This allows for more surface area to be in contact with the filter housing
and provides a lower impedance path between this housing and the back plane.
The back panel, in turn, has a high frequency ground strap connection to the
enclosure frame or earth ground.