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DFS1/DFS2 Power Installation Guide
Issue Number: 2
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. There is an increased risk when circuits extend outside a
building.
In general, 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. Ensure that every control wire has its own 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 mm², or 10 times the area of 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 analogue 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 4-13 and Figure 4-14.
If a digital port experiences a severe surge its protective trip may operate (O.L 1 trip code 26).
For continued operation after such an event, the trip can be reset automatically by setting parameter
Pr
10.034
to 5.
Figure 4-13 Surge suppression for digital and unipolar inputs and outputs
Figure 4-14 Surge suppression for analog and bipolar inputs and outputs
Surge suppression devices are available as rail-mounting modules, e.g. from Phoenix Contact:
Unipolar TT-UKK5-D/24 DC
Bipolar TT-UKK5-D/24 AC
These devices are not suitable for encoder signals or fast digital data networks because the
capacitance of the diodes adversely affects the signal. Most encoders have galvanic isolation of the
signal circuit from the motor frame, in which case no precautions are required. For data networks,
follow the specific recommendations for the network.
Signal from plant
Signal to drive
0V
0V
30V zener diode
e.g. 2xBZW50-15
Signal from plant
Signal to drive
0V
0V
2 x 15V zener diode
e.g. 2xBZW50-15
Summary of Contents for DFS 1
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