Electric Power Conversion Device Overcurrent Protection
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Solution Overview
Problem
When abnormalities are detected in electric power conversion devices, switching off all semiconductor switches can induce a voltage rise between direct current terminals, potentially exceeding the withstanding voltage and causing device destruction.
Innovation Solution
An electric power conversion device with a first circuit connected to a motor generator, a current detection circuit, a field coil excitation circuit, and a control circuit that detects induced electromotive force, allowing selective switching off of phases with overcurrent and controlled shutdown after the electromotive force falls below a predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all semiconductor switches are switched off after abnormalities are detected, then over current destruction is prevented, but voltage rise between direct current terminals occurs and may exceed the withstanding voltage
Solution Approach 1:
The control circuit performs preliminary actions by selectively turning off only the semiconductor switches in the phase where overcurrent is detected, rather than turning off all switches simultaneously. This preliminary selective action prevents the harmful voltage rise while still addressing the overcurrent issue in the affected phase.
Solution Approach 2:
The three-phase power conversion circuit is segmented into independent controllable phases. When overcurrent is detected in one phase, only the semiconductor switches in that specific phase are turned off, while switches in other phases remain operational. This segmentation allows localized protection without causing system-wide voltage rise.
2Reliability
If all semiconductor switches are switched off to prevent over current destruction, then device safety is improved, but induced electromotive force causes voltage rise that may destroy the device
Solution Approach 1:
The control circuit performs preliminary selective switching-off of only the affected phase before the voltage rise can occur. By detecting overcurrent and immediately turning off only the relevant semiconductor switches in that phase, the system prevents the induced electromotive force from causing dangerous voltage rise that would exceed the device's withstanding voltage capability.
Solution Approach 2:
The protection mechanism applies local quality control by targeting only the specific phase where overcurrent occurs. The semiconductor switches in the affected phase are turned off to provide local protection, while switches in healthy phases remain on to maintain overall system functionality and prevent global voltage rise.
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 solution prevents voltage rise and allows safe deactivation of the electric power conversion device, preventing element destruction.
Implementation Method 1
an electromotive force is induced in the stator coil of a motor, and a current by the electromotive force will flow into a battery side
Data Source
AI summary
An electric power conversion device includes: a first electric power conversion circuit, a current detection circuit, an electric power conversion circuit of field coil excite use, a control circuit, and detector which detects an induced electromotive force generated in the motor generator. In a case where an over current, is detected by the first electric power conversion circuit, the control circuit turns off a switching of a phase of the first electric power conversion circuit from which an over current s detected and a switching of the electric power conversion circuit of field coil excite use. After the value of an induced electromotive force by the motor generator falls below a predetermined value, the control circuit controls to stop a supply of electric power of all phases by the first electric power conversion circuit.