Eurotherm 582, Product Manual, Page: 41 / 47

Chapter 11 ‘CE’ EMC Responsibility
582/583/5831 11- 7
would typically be the attenuation provided by a standard metal cubicle) and screening any
control and signal cabling outside of the cubicle (including any optional tacho, encoders or
communications connections etc.).
On AC drives, in addition to screening the motor cable, any connections to the DC link must also
be screened/armoured, with the screen connected at both ends (e.g. to the protective earth of the
dynamic brake resistor).
Safety earthing always takes precedence over EMC earthing.
Screen to earth connections via 360
°
bonding is 75% more effective than earthing via pigtails.
The integrity of the screen should be maintained over the entire length of the cable. If the cable is
broken to insert contactors, chokes, fuses etc., then the screen must be connected over the
shortest possible distance. Note some hazardous area installations may preclude direct earthing at
both ends of the screen, in this case earth the other end via a 1
µ
F, 50VAC capacitor.
If a shielded cable is not available, lay unshielded motor cables in a metal conduit which will act
as a shield. The conduit must be continuous with a direct electrical contact at both ends. If links
are necessary use braid with a minimum cross sectional area of 10mm
2
.
Wall Mount (582/5831)
The cable between the wall mount drive module and the motor must be screened or armoured.
The screen/armour must be earthed at both ends by connecting it to both the motor frame and the
drive in 360
°
termination's. Ideally these will be via the glanded cable entry to the motor and
drive.
Screening of all the control and signal cables is required to comply with the most stringent
radiated emission limits of EN55011 Class B (including any optional tacho, encoders or
communications connections etc.). The screen integrity should be continuous right back to the
drive. Always minimise the length of screen stripped back to make this connection.
The screen
should only be connected at the drive end . If high frequency noise is still a problem, earth at
the non drive end via a 0.1
µ
F capacitor.
Cubicle Mount (582/583)
The cable between the cubicle and the motor must be screened or armoured. The screen/armour
must be earthed at both ends by connecting it to both the motor frame and the entrance to the
cubicle, ideally in 360
°
termination's via cable glands. Often the screens are terminated on a
power screen rail at the entrance to the cubicle using ‘U’ clips to achieve a near 360
°
screen
bond.
EARTHING
Wall Mount (582/5831)
A single point earthing policy is to be followed as shown in figure D. The motor protective earth
(PE) connection must run inside the screened cable between the drive and motor. This must be
connected at one end to the motor protective earth terminal and at the other to the drive
protective earth terminal in the cable gland box (Note, only one protective earth conductor is
permitted at each earth terminal contacting point). The filter should be
permanently earthed .
Local regulations may dictate the motor protective earth connection is connected locally. This
should be in addition to the protective earth connection made back to the drive module. The RF
impedance of the local motor earth connection will be significantly greater than that via the
screen/armour and will not introduce RF problems.
Safety earthing always takes precedence over EMC earthing.