12-2 Certification for the Converter
590 Series DC Digital Converter
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.
Control and signal cables for the encoder, all analogue inputs, and communications require
screening with the screen connected only at the VSD end. However, if high frequency noise is
still a problem, earth screen at the non VSD end via a 0.1μF capacitor.
Note: Connect the screen (at the VSD end) to the VSD protective point, and not to the control
board terminals.
Cabling Requirements
Note: Refer to Chapter 11: “Technical Specifications” for additional Cabling Requirements.
Planning Cable Runs
• Use the shortest possible motor cable lengths.
• Use a single length of cable to a star junction point to feed multiple motors.
• Keep electrically noisy and sensitive cables apart.
• Keep electrically noisy and sensitive parallel cable runs to a minimum. Separate parallel
cable runs by at least 0.25 metres. For runs longer than 10 metres, separation should be
increased proportionally. For example if the parallel runs were 50m, then the separation
would be (50/10) x 0.25m = 1.25m.
• Sensitive cables should cross noisy cables at 90°.
• Never run sensitive cables close or parallel to the motor, dc link and braking chopper circuit
for any distance.
• Never run supply, dc link or motor cables in the same bundle as the signal/control and
feedback cables, even if they are screened.
• Ensure EMC filter input and output cables are separately routed and do not couple across
the filter.
Increasing Motor Cable Length
Because cable capacitance and hence conducted emissions increase with motor cable length,
conformance to EMC limits is only guaranteed with the specified ac supply filter option using a
maximum cable length as specified in Chapter 11: “Technical Specifications”.
This maximum cable length can be improved using the specified external input or output filters.
Refer to Chapter 11: “Technical Specifications” - External Filters.
Screened/armoured cable has significant capacitance between the conductors and screen which
increases linearly with cable length (typically 200pF/m but varies with cable type and current
rating).
Long cable lengths may have the following undesirable effects:
• Producing increased conducted emissions which degrade the performance of the EMC filter
due to saturation.
• Causing RCDs (Residual Current Devices) to trip due to increased high frequency earth
current.
• Producing increased heating inside the EMC ac supply filter from the increased conducted
emissions.
These effects can be overcome by adding chokes or output filters at the output of the VSD.
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