TB Wood's WFC1000 Series, Инструкции по установке, эксплуатации и обслуживанию

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SECTION 5
INTERFERENCE SUPPRESSION MEASURES (ELECTROMAGNETIC COMPATIBILITY)
Electrical/electronic devices are capable of influencing or disturbing each other through connecting cables or
other metallic connections. “Electromagnetic Compatibility” consists of two parts, “interference resistance”
and “interference emission.” Correct installation of the inverter in conjunction with any possible local
interference suppression measures has a crucial effect on minimizing or suppressing mutual
interference.
The following notes refer to a power source that is not “contaminated” by high frequency interference. Other
measures may be necessary to reduce or suppress interference if the power source is “contaminated.” No
general valid recommendations can be given in such cases. Please consult TB Wood’s Electronics Applica-
tion Engineering if all recommended interference suppression measures should not produce the desired
result.
When dealing with RFI (radio frequency interference), the surface area of the conductors is a more critical
parameter than the cross-sectional area. Since high frequency interference does not flow through the entire
cross section of the conductor, but tends to stay toward its outer surface (skin effect), braided copper tapes of
equal cross section should be used.
The inverter and all components used for interference suppression, particularly the shield of the motor cable,
should be connected over as large a surface area as possible when passing over metallic surfaces. Remove
the paint from contact surfaces to assure a good electrical connection. See Figure 6 for recom-
mended connection technique.
Paint/varnish removed
Large contact area with shield
Shielded motor cable
Figure 6
A central grounding point should be used for interference suppression. The ground cables are routed
radially from this point. Loops in these lines are undesirable, and may lead to interference.
The shield cross section must not be damaged when the shield is connected to the continuing lines. This
would raise the RF resistance of the shield and as such, radiate rather than discharge the RF energy
traveling on the shield. Shields, particularly those on control cables, must not be routed through pin contacts
(plug connectors). When shielded cables must pass through a plug connection, the metallic hand guard of
the plug is used for the continuation of the shield. It is strongly recommended that the shield be
uninterrupted whenever possible.
Use a shielded motor cable which is grounded over a large surface area at both ends. The shield on this
cable should be uninterrupted. If a shielded motor cable can not be used, the unshielded motor line should
be laid in a metal conduit or duct which is uninterrupted and grounded at both ends.
When selecting shielded cable for use as motor leads, it is important to select a cable which is designed for
operation at the frequencies and power levels involved. Improper selection of motor cable can cause high
potential to exist on the shield. This could cause damage to the inverter or other equipment, as well as being
a potential safety hazard. Cables such as OLFlex
1 Series 150CY, 110CY, 110CS, 100CY, 100CS, and
540CP will work for this purpose. Siemens 2 Cordaflex (SM) also are acceptable. Some of these cables are
VDE approved only; others carry VDE, UL, CSA, and combinations of these ratings. Be sure to confirm that
the cable you are using meets the certification of the agency required.
If the installation requires the use of an output reactor, the reactor, like the line filter, should be placed as
close as possible to the inverter.
Control wires longer than 3 feet must be run in shielded cable, and the shield must be terminated at common
(COM) in the inverter. (Note that connection to COM, the circuit common, rather than earth ground, is
allowed because E-trAC
® inverters have isolated control inputs. If the inputs were not electrically isolated, the
shield would have to be connected to earth ground). If the signal run exceeds 30 feet, a 0-20 mA or 4-20 mA
signal should be used, as it will have better noise immunity than a low level voltage.
1. OLFlex Wire & Cable, 30 Plymouth Street, Fairfield, NJ 07004 (800) 774-3539
2. Siemens Energy and Automation, Inc., Power Cables, 3333 State Bridge Road, Atlanta, GA 30202 (800) 777-3539
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