Power System Resonance Conditions
Power system harmonics and system resonance conditions present challenges for industrial electrical systems with non-linear loads (for example, diode rectifiers, thyristor phase-controlled front-end converters, and so forth). Capacitive and inductive filters on a shared AC power source interact with source harmonics to create resonant current flows. This condition causes component stress, excess heating, and can result in reduced product life. Because the interaction of each load must be considered, system resonance conditions are challenging to predict.
For detailed information about power system resonance conditions and mitigation techniques, see Knowledgebase Answer ID 1093310.
PowerFlex 755T Resonance Detection Capabilities
PowerFlex®
755T active front-end products monitor for line-side resonance currents. Detection is a key to help prevent unexpected power system resonance failures.When system resonance is detected,
PowerFlex®
755T active front end drives and bus supplies continue operation and provide an early-warning of line-side resonance through alarm 14117 ‘CapHighResonance’.When power system resonance levels surpass thresholds for reliable operation, 14118 ‘CapOverResonance’ provides a fault. You have the option to configure the desired response to a system over resonance condition using parameter 0:453 [CapOvrRsncActn]. See publication 750-PM100 for firmware revision 6 and earlier or publication 750-RD101 for firmware revision 10 and later for more information.
Energy Pause Mode
If line-side resonance occurs while the line side converter is not modulating, commonly connected equipment is likely the cause. The energy pause feature is a useful way to disconnect the line side converter from the AC source when converter modulation is not required. Additionally, the energy pause feature shuts down peripheral devices to save energy during standby periods.
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