175 Sizing ad Selection of Frequency Converters 9.9 Centralised versus Decentralised Installation The most common form of installation is beyond doubt centralised installation of FC’s in control cabinets. The advantages of centralised control cabinet technology lie, above all, in the protected installation of the units and centralised access to them for power, control, maintenance, and fault analysis. With installation in the control cabinet, the primary aspect that must be taken into account is heat management, not only of the units but also of the whole installation. As a result of the heat dissipation in the control cabinet, additional cooling of the control cabinet may be necessary.
Depending on the FC manufacturer’s mounting regulations, minimum distances must be maintained above and below the unit and between the unit and adjacent components. For better heat removal, direct mounting on the rear wall of the control cabinet is recommended. Some manufacturers also specify minimum distances between the individual units. It is however, preferable to mount the units side-by-side if possible in order to utilise mounting surface area eff ectively. Fig. 9.9 Recommendations for mounting of converters (centralised solution) A disadvantage of centralised installation in some cases is the long cable lengths to the motors.
While the use of shielded cables defi nitely reduces the RFI eff ects of the motor cable, these eff ects are not completely eliminated. As an alternative to centralised installation, a decentralised approach to the lay-out of a facility can also be chosen. Here the FC is located very close to or directly on the motor. Motor cable lengths are thereby reduced to a minimum. In addition, decentralised installation off ers advantages in fault detection, since the relationship between the