Digitax HD M75X Series Installation and Technical Guide
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Issue Number: 5
A complete 360
termination of the shield to the terminal housing of the motor is beneficial.
From an EMC consideration it is irrelevant whether the motor cable contains an internal (safety) ground core, or if there is a separate external ground
conductor, or where grounding is through the shield alone. An internal ground core will carry a high noise current and therefore it must be terminated
as close as possible to the shield termination.
Figure 4-21 Grounding the motor cable shield
Unshielded wiring to the optional braking resistor(s) may be used provided the wiring runs internally to the enclosure. Ensure a minimum spacing of
300 mm (12 in) from the signal wiring and the AC supply wiring to the external EMC filter. If this condition cannot be met then the wiring must be
shielded.
Figure 4-22 Shielding requirements of optional external braking resistor
If the control wiring is to leave the enclosure, it must be shielded and the shield(s) clamped to the drive using the cable screen bracket as shown in
Figure 4-20. Remove the outer insulating cover of the cable to ensure the shield(s) make direct contact with the bracket, but keep the shield(s) intact
until as close as possible to the terminals. Alternatively, wiring may be passed through a ferrite ring, part number 3225-1004.
4.10.8 Variations in the EMC wiring
Interruptions to the motor cable
The motor cable should ideally be a single length of shielded or armored cable having no interruptions. In some situations it may be necessary to
interrupt the cable, as in the following examples:
•
Connecting the motor cable to a terminal block in the drive enclosure
•
Installing a motor isolator / disconnect switch for safety when work is done on the motor
In these cases the following guidelines should be followed.
Terminal block in the enclosure
The motor cable shields should be bonded to the back-plate using un-insulated metal cable-clamps which should be positioned as close as possible
to the terminal block. Keep the length of power conductors to a minimum and ensure that all sensitive equipment and circuits are at least 0.3 m (12 in)
away from the terminal block.
BR 2
BR 1
Optional external
braking resistor
Enclosure
Optional external
braking resistor
Enclosure
OR
BR 1
BR 2
Summary of Contents for Digitax HD M75 Series
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