Vascat MAC-HS 100, Operation And Maintenance Manual

Page: 46 / 64

OPERATION AND MAINTENANCE MANUAL
MAC-HS MOTORS
PAGE: 46
CODE: CTT32 EDITION: 04 RELEASE: SEPTEMBER 2020
Subject to technical changes without prior notice
5.2.3 Power cables
The inputs of the power cables that are to be connected on the motor terminal box strip and the converter terminals must comply
with current regulations. For the protection rating, type of cable-laying, allowed cable diameter, connection, etc., VASCAT
recommends the use of symmetrical structure screened cables in accordance with technical specification IEC TS 60034-25.
The cable screen must be made up of the maximum possible number of individual conductors and it must have good conductivity.
Twisted copper or aluminium screens are particularly suitable.
The following shows a schematic with the various examples of screened cables and their connections:
Figure 14: Recommended power cables and connections
As shown in the above figure, the power cable screen must be connected on both sides (motor and converter).
The screen connections must be made bearing in mind that they must cover a wide surface of the screen to create a 360°
contact using gland boxes for low impedance through a wide range of power levels. Make sure that the screen is HF (for high
frequencies). All the foregoing effectively reduces the voltages of the shaft and the housing, creating good derivation of the high
frequency currents. This will reduce the currents that will pass through the bearings. Consideration must be given to the fact that
the ends of the unscreened cable must be kept as short as possible.
PRECAUTION
Damages to the motor bearings
If the distribution of the earth conductors is not appropriate, current may flow through the bearings and deteriorate the parts of the
bearing in only a few months.
The following two figures show the recommended terminations for screened cables:
Scu
- Copper or aluminium screen
AFe
-Steel structure
Txfr
- transformer
Cv
– Converter
PEs
– Separate earth cable