Inverter Module Ground Segmentation for Surge Suppression
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Solution Overview
Problem
Motor drive apparatuses using inverter modules face issues with surge voltage-induced malfunctions and failures due to increased wiring inductance and high current capacity, especially when using wide bandgap semiconductors, which conventional layouts and wiring patterns struggle to protect effectively.
Innovation Solution
The motor drive apparatus incorporates the same number of inverter modules as phases, with each module featuring switching element pairs connected in series and a surge suppression element between power and control ground terminals to mitigate surge voltage, reducing the risk of malfunction and failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If inverter modules are connected in parallel to increase current capacity, then the current handling capability is improved, but the wiring inductance increases causing surge voltage to worsen
Solution Approach 1:
The patent divides the ground connection path into separate segments: power ground terminals for switching elements and control ground terminals for gate drive circuits. This segmentation allows independent optimization of each ground path, reducing the overall wiring inductance and suppressing surge voltage while maintaining high current capacity through parallel inverter module connections.
Solution Approach 2:
The patent introduces separate ground terminals as intermediary connection points between the parallel inverter modules and the power supply/control circuits. These intermediate ground terminals provide dedicated low-inductance paths that mediate the connection, preventing surge voltage from propagating through the entire parallel structure while maintaining current capacity.
2Speed
If switching elements made from wide bandgap semiconductor are used to speed up operation, then the switching speed is improved, but the current changing rate increases causing surge voltage to worsen
Solution Approach 1:
The patent segments the ground connection system into power ground and control ground terminals, creating separate low-inductance paths for high-speed switching currents and control signals. This segmentation reduces the overall inductance encountered by fast-switching wide bandgap semiconductor devices, suppressing surge voltage while maintaining high switching speed.
3Device complexity
If conventional wiring patterns are used to protect against surge voltage, then the layout is simple, but the wiring inductance increases causing surge voltage to worsen
Solution Approach 1:
The patent applies segmentation by creating distinct power ground and control ground terminal structures rather than using conventional unified wiring patterns. This segmented approach reduces wiring inductance and suppresses surge voltage while maintaining reasonable layout simplicity through systematic terminal arrangement.
Solution Approach 2:
The patent implements local quality optimization by providing dedicated ground terminals with low inductance characteristics specifically at the locations where switching elements and gate drive circuits connect. This localized ground terminal structure reduces surge voltage at critical points without requiring complete redesign of the entire wiring pattern.
Data Source
AI summary
There are provided the same number of inverter modules as the number of phases of a motor, and an inverter control unit that generates PWM signals used to drive the inverter modules in PWM. Three phase outputs from each of the inverter modules are coupled to form a phase output signal for one phase of the motor while capacitors are mounted between control GNDs of the inverter modules and power GNDs of the inverter modules. Consequently, even if a surge voltage is generated in a GND wiring at the time of a switching operation of switching elements in the inverter modules, the application of the surge voltage to the switching elements can be suppressed.