23/126
Siemens Building Technologies
SED2 variable speed drives
CM1U5192en
HVAC Products
Electrical installation
01.2002
4.2
EMC-compatible installation
The SED2 VSDs operate in environments where they may be exposed to high levels of
electromagnetic interference (EMI). Normally, good installation practices ensure safe
and interference-free operation. However, should problems associated with EMI occur,
follow the guidelines below:
Ø
Ensure good electrical contact between the mounting plate and the metal housing
of the VSD via the mounting screws.
Ø
Use serrated lock washers and electrically conductive mounting plates.
Ø
If a footprint EMC filter is used, fit it under the VSD and ground it via the metal
backplate. When connecting the EMC filter to the inputs of the VSD, use shielded
cables and make sure that they are correctly grounded using cable clamps.
4.2.1
EMC-compatible wiring
Ø
Use shielded cables also inside control cabinets.
Ø
Ensure that all equipment in the control cabinet is properly grounded. Thus, make
sure that all equipment is connected by short, thick grounding conductors to a
common grounding point (flat ribbon lines are best) or bus bar.
Ø
Ensure that any control equipment (e.g. PLC or BACS
1
) connected to a VSD is
connected with a short, thick cable to the same ground or grounding point as the
variable speed drive itself.
Ø
Use only shielded motor and control cables. The shielding must be continuous.
Ø
Connect motor and control cables to ground at both ends.
Ø
Lay control, mains, and motor cables separately by routing them in separate cable
ducts and maintaining a minimum clearance of at least 200 mm (see diagram
below). If you must cross cables, run them at an angle of 90° if possible.
Ø
Motor cables should be as short as possible and should not exceed 25 m.
Ø
Connect the neutral conductor for the motors controlled by the variable speed
drives directly to the ground connection (PE) of the associated VSD.
Ø
Use flat ribbon cables, as they have a lower impedance at high frequencies.
Ø
Avoid pigtails. Use only grounding clamps to bond the screen (see diagram below).
51
9
1
Z
01
Ø
Check that the contactors in the control cabinet are suppressed—either with RC
circuits for AC contactors, or flywheel diodes for DC contactors—and fit the
suppressors to the coils. Varistor surge voltage protectors are also effective. This is
important if the contactors are controlled by the variable speed drive relay.
1
SPS: Programmable controllers
BACS: Building automation and control system; sometimes incorrectly referred to as BMS (building
management system)
