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Other Layout Considerations
The proximity between the source and victim circuit has a large effect on radiated coupling. The electromagnetic
fields produced by drive modules falls off rapidly with distance from the cabling/enclosure. It should be
remembered that the radiated fields from EMC compliant drive systems are measured at least 10m from the
equipment over the frequency band 30 to 1000 MHz (as required by EN55011, referenced by the generics and
the drive product specific standard). Any equipment placed closer to the drive system than this will see larger
magnitude fields, particularly very close to the drive. No magnetic/electric field sensitive equipment should be
placed within 0.25m of the following parts of a drive system:
-
620 Drive module
-
EMC output filters
-
Input or output chokes/transformers
-
Cable between 620 Frequency Inverter and Motor (even when screened/armoured)
-
Connections to external braking chopper and resistor (even when screened/armoured)
-
AC/DC brushed motors (due to commutation)
-
DC link connections (even when screened/armoured)
-
Relays and contactors (even if they are suppressed)
Often the coupling between electrically 'noisy' and 'sensitive' cables is a problem. This can be minimised by
separating parallel runs by at least 0.25m, and minimising the length of parallel runs. For long parallel runs (>10
m) the separation should be increased proportionally. For example if the parallel runs were 50 m then the
separation would be (50/10)
×
0.25 m = 1.25 m.
In addition the coupling between two cables which must cross is minimised if they cross over at 90
°
. Hence
sensitive cables should cross the cables to the motor, DC link and braking chopper circuit at 90
°
, and should
never be run close to them or in parallel for any great length.
Never run supply, DC link or motor cables in the same bundle as the signal/control and feedback cables, even if
they are screened.
From experience the following equipment is defined as particularly sensitive and care must be taken in the
installation:
-
Any transducers which produce low level analogue outputs (<1 volt) e.g. load cells, strain gauges,
thermocouples, piezoelectric transducers, anometers, LVDT's
-
A.M. radios (long and medium wave only)
-
Video cameras and closed circuit TV
-
Office personal computers
-
Capacitive devices such as proximity sensors and level transducers
-
Mains borne communication systems
-
Equipment not suitable for operation in the intended EMC environment i.e. with insufficient immunity to
new EMC standards
This manual was downloaded on www.sdsdrives.com
+44 (0)117 938 1800 - [email protected]
