Inverter Phase Leg Test Circuit with Dynamic Capacitance
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Solution Overview
Problem
Conventional testing of power semiconductor devices requires oversized capacitors for inverter testing, leading to increased costs, and smaller inductance values for load impedance can impact turn on/turn off current values, necessitating an improved system for characterizing circuits without altering the circuit configuration.
Innovation Solution
A circuit with a capacitor coupled between an inverter power input and a switch module, including a pair of IGBTs and relays, a controller to selectively control current flow through active and passive elements, and a load with selectable inductance, allowing for precise testing of inverter phase legs with adjustable capacitance and inductance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If oversized capacitors are used for inverter testing, then testing accuracy is improved, but cost increases
Solution Approach 1:
The patent implements a dynamically switchable capacitor network where capacitors can be selectively connected or disconnected during different phases of the double-pulse test. The controller dynamically adjusts the capacitor configuration based on test requirements, allowing accurate measurement of both turn-on and turn-off current values without requiring oversized capacitors to be permanently connected.
Solution Approach 2:
The capacitor bank is divided into multiple separate capacitor elements that can be independently controlled. During the turn-on current test, specific capacitors are connected while others remain disconnected, and vice versa for turn-off current testing. This segmentation allows precise control of capacitance values to match test requirements without using oversized capacitors for both conditions simultaneously.
2Device complexity
If smaller inductance values are used for load impedance, then device complexity is reduced, but current measurement accuracy deteriorates
Solution Approach 1:
The patent employs a controller that dynamically changes the inductance parameter of the load impedance based on the specific test phase. During turn-on current measurement, one inductance value is selected, while during turn-off current measurement, a different inductance value is selected. This parameter switching allows accurate current measurements without requiring complex fixed inductance configurations.
Solution Approach 2:
The load impedance inductance is made dynamically adjustable through electronic switching between different inductance values. The controller switches between inductance configurations at appropriate times during the test cycle, enabling accurate current measurements for both device turn-on and turn-off events without requiring a permanently complex inductance network.
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 enables accurate and reproducible testing of power semiconductor devices under various conditions, improving characterization without increasing costs or altering the circuit configuration, and allows for dynamic and static tests, including double-pulse tests.
Implementation Method 1
A capacitor may be coupled between a power input of the inverter and a switch module
Implementation Method 2
The switch module may include a pair of Insulated Gate Bipolar Transistors (IGBT) that are arranged to, responsive to being in a conductive state, permit current flow in opposite directions
Data Source
AI summary
A system for testing a phase leg of an inverter includes a load coupled to an output terminal of the phase leg. A test circuit includes a capacitor coupled between an inverter power input and a switch module operative to couple the capacitor to the load. The circuit further includes a switch operative to select a polarity of a voltage across the capacitor. The circuit also includes a pair of switching elements operative to selectively couple the first terminal to the inverter power input and the inverter power return. The components can be operated by a controller configured to selectively couple the load to the inverter power and return terminals, selectively charge and couple the capacitor to the load, and interface with the inverter to control a path of current flow through active and passive elements of the phase leg.