Certification for the Drive 10-1
650V AC Drive
Chapter 10 CERTIFICATION FOR THE DRIVE
Requirements for EMC Compliance
All Variable Speed Drives (VSDs) potentially produce electrical emissions which are radiated
into the environment and conducted back into the ac supply. VSDs are inherently immune to any
additional external electrical noise. The following information is provided to maximise the
Electro Magnetic Compatibility (EMC) of VSDs and systems in their intended operating
environment, by minimising their emissions and maximising their immunity.
Minimising Radiated Emissions
EN50081-1 (1992)/EN50081-2 (1994)/EN55011/EN55022 radiated emission measurements are
made between 30MHz and 1GHz in the far field at a distance of 10 to 30 metres. Limits lower
than 30MHz or in close proximity are not specified. Emissions from individual components tend
to be additive.
• Use a screened/armoured cable between VSD/cubicle and motor containing the motor
protective earth (PE) connection. It should have a 360° screen termination. Earth screen at
both ends connecting to the motor frame and cubicle (or gland box if wall mounted).
Maintain the screen integrity using 360° terminations.
Note:
Some hazardous area installations may preclude direct earthing at both ends of the
screen, in this case earth one end via a 1µF 50Vac capacitor, and the other as normal.
• Keep unshielded cable as short as possible inside the cubicle.
• Always maintain the integrity of the shield.
• If the cable is interrupted to insert contactors etc., re-connect the screen using the shortest
possible route.
• Keep the length of screen stripped-back as short as possible when making screen
connections.
• Ideally use 360° screen terminations using cable glands or ‘U’ clips on power screen rails.
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 to the VSD and motor
housing. If links are necessary, use braid with a minimum cross sectional area of 10mm
2
.
Note:
Some motor gland boxes and conduit glands are made of plastic, if this is the case, then
braid must be connected between the screen and the chassis. In addition at the motor
end, ensure that the screen is electrically connected to the motor frame since some
terminal boxes are insulated from the frame by gasket/paint.
Earthing Requirements
IMPORTANT: Protective earthing always takes precedence over EMC earthing.
Protective Earth (PE) Connections
Note:
In accordance with installations to EN60204, only one protective earth conductor is
permitted at each protective earth terminal contacting point.
Local wiring regulations may require the protective earth connection of the motor to be
connected locally, i.e. not as specified in these instructions. This will not cause shielding
problems because of the relatively high RF impedance of the local earth connection.
EMC Earth Connections
For compliance with EMC requirements, we recommend that the “0V/signal ground” is
separately earthed. When a number of units are used in a system, these terminals should be
connected together at a single, local earthing point.
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