Power Converter Diode Mediator for Short-Circuit Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electric vehicles equipped with permanent-magnet synchronous motors, short-circuit faults in power converters can lead to continuous flow of high short-circuit currents due to induced voltages, causing damage to the faulty portion or motor, especially when the contactor fails to interrupt the current.
Innovation Solution
A power converter system with an inverter, an opening/closing unit, and a controller that includes a voltage detector to monitor and manage voltage conditions, preventing further damage by controlling the contactor's operation and reducing the induced voltage when abnormal conditions are detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contactor is provided to interrupt the short-circuit current, then the damage of the power converter can be prevented, but the short-circuit current cannot be interrupted when the contactor fails or the current exceeds the interruption capacity
Solution Approach 1:
A diode is introduced as an intermediary component connected between the motor terminals and the neutral point. This diode provides an alternative current path that allows the short-circuit current to be safely dissipated through the motor winding resistance, preventing damage to the power converter even when the contactor fails to interrupt the current.
Solution Approach 2:
The invention utilizes the motor winding resistance, which normally represents a source of copper loss and heat generation, as a beneficial element to dissipate the short-circuit current energy. By allowing the short-circuit current to flow through the motor winding, the harmful current is converted into useful heat dissipation that protects the power converter from damage.
2Reliability
If the power converter is designed to withstand the induced voltage, then the power converter can operate normally, but high short-circuit currents can still flow when terminals are short-circuited
Solution Approach 1:
The diode acts as a mediator that redirects the short-circuit current through a safe path involving the motor winding and neutral point, preventing the current from causing damage while allowing the power converter to maintain its normal operational stability.
Solution Approach 2:
The current path is segmented into different routes: normal operation current flows through the inverter, while short-circuit current is redirected through the diode and motor winding path. This segmentation allows the system to handle different current conditions separately and safely.
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
The system effectively prevents damage to the power converter or motor by interrupting the short-circuit current and reducing the induced voltage, even when the contactor is unable to turn off the current, thereby mitigating potential overheating or burning issues.
Implementation Method 1
an induced voltage is inevitably generated at a terminal of the motor during rotation of the rotor by an action of magnetic flux of the permanent magnet incorporated in the rotor of the motor
Implementation Method 2
a diode, allowing a current to flow in only one direction, is connected between a terminal of the motor and a neutral point of the inverter
Implementation Method 3
the short-circuit current due to the induced voltage of the motor keeps flowing through the faulty portion (short-circuit location) of the power converter where the short-circuit fault has occurred. If this state is left unsettled, there is a possibility that the damage of the faulty portion of the power converter becomes worse or the faulty portion or the motor becomes hot
Data Source
AI summary
In a power converter a controller determines that an AC motor is in an abnormal state when a voltage of each phase of the AC motor detected by a voltage detector is in an unbalanced state where the voltage exceeds a predetermined value, and turns an opening/closing unit OFF to prevent damage generated in the AC motor from becoming worse. Moreover, the controller determines abnormality of the opening/closing unit based on a current of each phase detected by a current detector, and the controller performs control to reduce the number of revolutions of the AC motor upon determining that at least one of the AC motor and the opening/closing unit is in an abnormal state.