Shielded Inverter Cable High-Pass Filtering for Current Loss Reduction
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Solution Overview
Problem
High frequency current coupling to conductive shielding in power cables causes significant losses and heating, limiting current carrying capability and disrupting other electronics, especially in systems with high switching frequencies.
Innovation Solution
A cabling system with a high pass filter comprising capacitance connected to the conductive shielding to attenuate current below a predetermined frequency, using frequency-dependent current limiting impedance to prevent coupling to the shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the conductive shielding is directly or indirectly connected to the chassis to provide a low impedance path for high frequency current, then high frequency common mode current is diverted from disrupting electronics, but torque producing current creates magnetic coupling to the shielding causing significant losses and heating
Solution Approach 1:
A high pass filter is introduced as an intermediary component between the conductive shielding and the chassis connection. This filter selectively allows high frequency common mode current to pass through to the chassis while blocking low frequency torque producing current from coupling to the shielding, thus eliminating both the electromagnetic disruption and the power losses simultaneously
Solution Approach 2:
The impedance characteristics of the connection between the conductive shielding and chassis are changed by introducing a frequency-dependent high pass filter. This creates a low impedance path for high frequency current while maintaining high impedance for low frequency current, resolving the contradiction by making the impedance dynamic rather than static
2Loss of energy
If the conductive shielding is opened at one or both ends to prevent circulating current, then power losses and heating are reduced, but significant high frequency common mode currents travel through the rest of the system disrupting other electronics
Solution Approach 1:
The high pass filter acts as a mediator that allows the conductive shielding to remain closed (preventing circulating current and power losses) while simultaneously directing high frequency common mode current to the chassis connection, preventing electromagnetic disruption to electronics
3Productivity
If the distance between the main conductor and the conductive shielding is made as small as possible to enable magnetic field cancellation, then current carrying capability is improved, but the insulator thickness requirement prevents achieving optimal cancellation
Solution Approach 1:
The high pass filter extracts the problematic low frequency current component from the conductive shielding, eliminating the need for magnetic field cancellation through close spacing. This allows the insulator thickness to be determined by electrical insulation requirements rather than magnetic cancellation optimization
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces high frequency current coupling, minimizing losses and heating, and maintains efficient current carrying capacity while protecting other electronics.
Implementation Method 1
a high pass filter which comprises capacitance electrically connected to the conductive shielding configured to attenuated current less than a predetermined frequency from coupling to the conductive shielding. The attenuation is achieved via a frequency dependent current limiting impedance of the capacitance.
Implementation Method 2
The attenuation is achieved via a frequency dependent current limiting impedance of the capacitance.
Implementation Method 3
an outer conductor (conductive shielding) is connected either directly or indirectly to a chassis of the electric machine or the inverter. This provides a low impedance path for the high frequency current to travel.
Implementation Method 4
the torque producing current or flux modifying current flowing in the main conductor creates a magnetic field which couples to the conductive shielding as an air core transformer effect. This coupled current in the conductive shielding increases with magnitude of the AC current and frequency
Data Source
AI summary
A cabling system having a shielded cable for connecting an inverter and an electric machine is provided. The conductive shielding is connectable, either directly or indirectly, to the chassis of the inverter and the chassis of the electric machine such as indirectly, via a cable connector chassis. The cabling system further comprise high pass filter which comprises capacitance electrically connected to the conductive shielding configured to attenuated current less than a predetermined frequency from coupling to the conductive shielding. The attenuation is achieved via a frequency dependent current limiting impedance of the capacitance. The current less than the predetermined frequency is caused by torque producing current and/or flux modifying current. The cable connector chassis may comprise at least one high pass filter to connect serially with at least one cable inserted therein, respectively.