Emerson FXMP25 User Manual page 22

EN 61800-3:2004 defines the following:
• The first environment is one that includes residential premises. It also includes
establishments directly connected without intermediate transformers to a low-
voltage power supply network which supplies buildings used for residential
purposes.
• The second environment is one that includes all establishments other than those
directly connected to a low-voltage power supply network which supplies buildings
used for residential purposes.
• Restricted distribution is defined as a mode of sales distribution in which the
manufacturer restricts the supply of equipment to suppliers, customers or users who
separately or jointly have technical competence in the EMC requirements of the
application of drives.
4.6.1 Surge immunity of control circuits - long cables and connections outside
a building
The input/output ports for the control circuits are designed for general use within
machines and small systems without any special precautions.
In applications where they may be exposed to high-energy voltage surges, some
special measures may be required to prevent malfunction or damage. Surges may be
caused by lightning or severe power faults in association with grounding arrangements
which permit high transient voltages between nominally grounded points. This is a
particular risk where the circuits extend outside the protection of a building.
As a general rule, if the circuits are to pass outside the building where the drive is
located, or if cable runs within a building exceed 30 m, some additional precautions are
advisable. One of the following techniques should be used:
1. Galvanic isolation, i.e. do not connect the control 0 V terminal to ground. Avoid loops in
the control wiring, i.e. ensure every control wire is accompanied by its return (0 V) wire.
2. Shielded cable with additional power ground bonding. The cable shield may be
connected to ground at both ends, but in addition the ground conductors at both
ends of the cable must be bonded together by a power ground cable (equipotential
bonding cable) with cross-sectional area of at least 10 mm
the signal cable shield, or to suit the electrical safety requirements of the plant. This
ensures that fault or surge current passes mainly through the ground cable and not
in the signal cable shield. If the building or plant has a well-designed common
bonded network this precaution is not necessary.
3. Additional over-voltage suppression - for the analog and digital inputs and outputs, a
zener diode network or a commercially available surge suppressor may be
connected in parallel with the input circuit as shown in Figure 4-3 and Figure 4-4.
Figure 4-3 Surge suppression for digital and unipolar inputs and outputs
22
Signal from plant
0V
www.controltechniques.com
2
Signal to drive
30V zener diode
e.g. 2xBZW50-15
0V
, or 10 times the area of
FXMP25 User Guide
Issue Number: 3