12-2
Certification for the Servo Drive
07-01-08-02-E-V0500 631 Digital Servo Drive
Control and signal cables for the encoder and all analog inputs normally 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 0.1
µ
F capacitor.
Note:
Connect the screen (at the VSD end) to the VSD protective earth 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 and braking chopper circuit for any
distance.
•
Never run supply or motor cables in the same bundle as the signal/control and feedback
cables, even if they are screened.
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 internal ac supply filter option.
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:
•
Tripping on `overcurrent’ as the cable capacitance is charged and discharged at the
switching frequency.
•
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.
EMC Installation Options
The unit, when installed for Class A or Class B operation, will be compliant with EN55011
(1991)/ EN55022 (1994) for radiated emissions, as described below.
Screening & Earthing (wall mounted, Class A)
IMPORTANT:
This unit must be mounted inside a suitable control cubicle requiring a tool for opening to
maintain compliance with the European Electrical Safety Standard VDE0160 (1994)
/EN50178 (1998).
The unit is installed for Class A operation when wall mounted inside a cubicle and having
complied with all cabling requirements.
