Specifications

The power line noise emissions associated with
variable frequency and variable speed drives can
cause disturbances in nearby equipment. Typical
disturbances include:
• Dimmer and ballast instability
• Lighting disturbances such as flashing
• Poor radio reception
• Poor television reception
• Instability of control systems
• Flow meter totalizing
• Flow metering fluctuation
• Computer system failures including the loss of
data
• Thermostat control problems
• Radar disruption
• Sonar disruption
RFI
Three-phase filters are supplied as an option for
factory mounting in the compressor power panels.
They use a combination of high frequency
inductors and capacitors to reduce noise in the
critical 150 kHz to 30 MHz frequency range. The
inductors act as open circuits and the capacitors
act as short circuits at high frequencies while
allowing the lower power line frequencies to pass
untouched. The filters assist with cost effective
compliance to Electro Magnetic Compatibility
(EMC) directives, in a compact, efficient, light-
weight design. The high common mode and
differential mode reduction in the critical 150kHz
to 30MHz frequencies assures that potential
interference from AC drives is reduced or
eliminated.
The filters are current-rated devices. In order to
properly size a filter, it is necessary to know the
operating voltage, and the input current rating of
the drive. No derating or re-rating is necessary
when applying the filter at voltages that are less
than or equal to the maximum voltage listed on the
filter.
The IEEE 519-1991 Standard
The Institute of Electrical and Electronics
Engineers (IEEE) has developed a standard that
defines acceptable limits of system current and
voltage distortion. A simple form is available from
McQuay that allows McQuay to determine
compliance with IEEE 519-1991.
Line reactors, isolation transformers, or phase-
shifting transformers can be required on some
installations.
Figure 24, Typical WMC Power Wiring
Catalog WMC-4 39