If the screen is to be placed on a mounting plate for the frequency converter, the mounting plate must be made of metal, because the screen currents
have to be conveyed back to the unit. Moreover, ensure good electrical contact from the mounting plate through the mounting screws to the frequency
converter chassis.
When unscreened cables are used, some emission requirements are not complied with, although the immunity requirements are observed.
In order to reduce the interference level from the entire system (unit + installation), make motor and brake cables as short as possible. Avoid placing
cables with a sensitive signal level alongside motor and brake cables. Radio interference higher than 50 MHz (airborne) is especially generated by the
control electronics.
2.9.2 Emission Requirements
According to the EMC product standard for adjustable speed frequency converters EN/IEC61800-3:2004 the EMC requirements depend on the intended
use of the frequency converter. Four categories are defined in the EMC product standard. The definitions of the four categories together with the
requirements for mains supply voltage conducted emissions are given in the table below:
Category
Definition
Conducted emission requirement
according to the limits given in
EN55011
C1
frequency converters installed in the first environment (home and office) with a supply
voltage less than 1000 V.
Class B
C2
frequency converters installed in the first environment (home and office) with a supply
voltage less than 1000 V, which are neither plug-in nor movable and are intended to be
installed and commissioned by a professional.
Class A Group 1
C3
frequency converters installed in the second environment (industrial) with a supply volt-
age lower than 1000 V.
Class A Group 2
C4
frequency converters installed in the second environment with a supply voltage equal to
or above 1000 V or rated current equal to or above 400 A or intended for use in complex
systems.
No limit line.
An EMC plan should be made.
When the generic emission standards are used the frequency converters are required to comply with the following limits:
Environment
Generic standard
Conducted emission requirement ac-
cording to the limits given in
EN55011
First environment
(home and office)
EN/IEC61000-6-3 Emission standard for residential, commercial and
light industrial environments.
Class B
Second environment
(industrial environment)
EN/IEC61000-6-4 Emission standard for industrial environments.
Class A Group 1
2 Introduction to VLT HVAC Drive
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HVAC Drive Design Guide
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