Integrated Motor-Inverter Windings for Balanced Phase Currents
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Solution Overview
Problem
Integrating a three-phase inverter with an electric motor in a single housing poses challenges due to uneven loading of motor coils and power switches, high current requirements, and thermal issues, which affect efficiency and reliability, particularly in high power output systems.
Innovation Solution
The motor windings are divided into galvanically isolated sections with identical electrical resistance, connected to power switches forming half-bridge legs, ensuring equal current flow through each switch and reducing parallel connections, with current sensors measuring only a portion of the phase current to minimize size and thermal hot spots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If motor windings are connected with power switches in a conventional three-phase inverter configuration, then high power output is achieved, but uneven loading occurs causing all motor coils and power switches not to be used to their full capability
Solution Approach 1:
The motor windings are divided into multiple independent winding sections (e.g., 6 sections for a 4-pole motor) that are galvanically isolated from each other. Each winding section is connected to its own dedicated power switches in a half-bridge configuration, eliminating the conventional three-phase parallel connection and achieving symmetrical current distribution across all power switches and motor coils.
2Power
If power switches are connected in parallel to handle high currents, then high power output is achieved, but thermal hot spots increase and reliability decreases
Solution Approach 1:
Instead of connecting power switches in parallel to handle high currents, the invention segments the power circuit into multiple independent half-bridge legs, each handling a portion of the total power. This distributes the thermal load across multiple independent paths, eliminating concentrated hot spots and improving reliability.
3Measurement precision
If current sensors are designed to measure complete motor phase currents, then accurate motor control is achieved, but sensor size and cost increase
Solution Approach 1:
The current measurement function is segmented by placing individual current sensors in series with each winding section instead of measuring the total phase current. Each sensor only measures the current of its associated winding section, which is a fraction of the total phase current, thereby reducing sensor size and cost while maintaining sufficient control accuracy through aggregated measurement data.
4Power
If connections between motor and inverter are designed for heavy currents, then high power transmission is achieved, but connection size increases and thermal issues worsen
Solution Approach 1:
The power transmission path is segmented into multiple independent connection paths, each carrying a portion of the total current. This distributes the current load across multiple smaller connections rather than requiring a single large connection, reducing connection dimensions and thermal issues while maintaining the same total power transmission capability.
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
This configuration achieves balanced current distribution, reduces the size of current sensors and connections, enhances efficiency, and increases reliability by minimizing torque ripple and thermal issues, while maintaining compactness and functional safety.
Implementation Method 1
a rotor with Npp number of pole pairs rotatable disposed against the stator magnetic field generated by currents in stator windings
Data Source
Figure 1
Figure 2~3
AI summary
An electric machine (1) with integrated electronics operating as electric motor-generator in electrically powered systems has a motor portion (11) with a plurality of coils (10) so connected, to form a number of isolated winding sections (12) with multi-phase configuration, which are substantially identical between each other. An inverter portion (2) has a plurality of power switching elements (5, 6) forming a power stage with a number of half bridge legs (18). Output connectors (7) of said half bridge legs (18) are electrically connected to terminals (13) of individual coils (10). A control board in an ECU of the inverter portion (2) provides such a control algorithm and signals for power switching, that the coils (10) which belong to the same phase of the motor (1) have the same terminal voltages. Current sensors (8, 9) for measuring the motor phase currents are so arranged to measure the currents through only two coils (10) from the plurality of coils (10) in the stator (17). The size, the measuring range of current sensors (8, 9) and unwanted braking torque during faults in motor windings or in power switches are reduced by the number of isolated winding sections (12). Therefore the motor-generator (1) becomes more compact and has a higher functional safety.