Connect the different ground systems at the lowest possible conductor impedance. The
lowest possible conductor impedance is obtained by keeping the conductor as short as
possible and by using the greatest possible surface area.
The metal cabinets of the different devices are mounted on the cabinet rear plate using
the lowest possible HF impedance. This prevents having different HF voltages for the
individual devices and prevents the risk of radio interference currents running in
connection cables that may be used between the devices, as radio interference is
reduced.
In order to obtain a low HF impedance, use the fastening bolts of the devices as HF
connections to the rear plate. It is necessary to remove insulating paint and the like from
the fastening points.
5.6 Extra protection (RCD)
Earth Leakage Circuit Breaker (ELCB) relays, multiple protective grounding or grounding
can be used as extra protection, provided that local safety regulations are complied with.
In the case of a ground fault, a DC component may develop in the fault current.
If ELCB relays are used, local regulations must be observed. Relays must be suitable for
protection of 3–phase equipment with a bridge rectifier and for a brief discharge on
power-up.
See also the section Special Conditions in the Design Guide.
5.7 Torque
When tightening all electrical connections, it is very important to tighten with the correct
torque. Too low or too high torque results in a bad electrical connection. Use a torque
wrench to ensure correct torque.
Figure 61: Torque wrench
See Technical Specifications Chapter for details.
5.8 Shielded cables
It is important that shielded and armored cables are connected properly to ensure high
EMC immunity and low emissions.
Connection can be made by either cable connectors or clamps:
5 Electrical Installation
Aquavar
®
Intelligent Pump Controller - 150 HP to 600 HP INSTRUCTION MANUAL 51
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