Danfoss VLT FC 103, Руководство по эксплуатации

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3.4.8 Shielding against Electrical Noise
To ensure best EMC performance, mount the EMC metal
cover before mounting the mains power cable.
NOTICE
The EMC metal cover is only included in units with an
RFI filter.
175ZT975.10
Illustration 3.53 Mounting of EMC Shield.
3.5 Control Wiring Connection
•
Isolate control wiring from high power
components in the frequency converter.
•
If the frequency converter is connected to a
thermistor for PELV isolation, optional thermistor
control wiring must be reinforced/double
insulated. A 24 V DC supply voltage is
recommended.
3.5.1 Access
All terminals to the control cables are located underneath
the LCP on the inside of the frequency converter. To
access, open the door (IP21/54) or remove the front panel
(IP20).
3.5.2 Using Screened Control Cables
Danfoss recommends braided screened/armoured cables to
optimise EMC immunity of the control cables and the EMC
emission from the motor cables.
The ability of a cable to reduce the incoming and
outgoing radiation of electric noise depends on the
transfer impedance (Z
T
). The screen of a cable is normally
designed to reduce the transfer of electric noise; however,
a screen with a lower transfer impedance (Z
T
) value is
more effective than a screen with a higher transfer
impedance (Z
T
).
Transfer impedance (Z
T
) is rarely stated by cable manufac-
turers, but it is often possible to estimate transfer
impedance (Z
T
) by assessing the physical design of the
cable.
Transfer impedance (Z
T
) can be assessed on the basis of
the following factors:
•
The conductibility of the screen material.
•
The contact resistance between the individual
screen conductors.
•
The screen coverage, i.e. the physical area of the
cable covered by the screen - often stated as a
percentage value.
•
Screen type, i.e. braided or twisted pattern.
Installation Operating Instructions
MG16J202 Danfoss A/S © Rev. 05/2014 All rights reserved. 49
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