Motor Drive Device Short-Circuit Control for Surge Voltage Prevention
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Solution Overview
Problem
In high-load motor states, switching between all-phase short-circuiting of upper and lower arm switching elements can generate high surge voltages due to transient currents exceeding normal operating levels, posing a risk to switching element reliability.
Innovation Solution
A motor drive device and method that include a current determination unit and a short-circuit control unit to alternately switch all upper and lower arm switching elements only when the motor current is equal to or smaller than a threshold value, preventing excessive current-driven surge voltage generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If all-phase short-circuiting of upper and lower arm switching elements is alternately switched in high-load motor state, then the motor drive function is improved, but high surge voltage is generated that exceeds switching element withstand voltage
Solution Approach 1:
The patent changes the control parameter by introducing current threshold detection. The short-circuiting operation is conditionally executed based on whether motor current exceeds a predetermined threshold. This parameter-based control prevents surge voltage generation while maintaining motor drive functionality, resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent implements feedback control by continuously monitoring motor current and using this information to control the switching element operation. When current exceeds the threshold, the control unit suppresses the short-circuiting operation, creating a closed-loop system that prevents damage while maintaining drive function, thus resolving the reliability-productivity contradiction.
2Ease of operation
If switching elements are alternately switched between all-on states in short-circuiting operation, then current control capability is improved, but transient current exceeding normal operating levels generates harmful surge voltage
Solution Approach 1:
The patent applies preliminary anti-action by detecting current threshold violations before dangerous surge voltage can occur. The control unit proactively suppresses the short-circuiting operation when threshold is exceeded, preventing the harmful effect rather than reacting to it after occurrence, thus eliminating surge voltage while maintaining control capability.
Solution Approach 2:
The patent converts the potentially harmful transient current into a useful control signal. By using current threshold detection, the harmful high current condition becomes the trigger for protective action, transforming what would be a damaging event into a controlled operational parameter that enhances overall system safety and control.
Data Source
AI summary
Provided is a motor drive device comprising a motor control unit that controls a plurality of upper arm-side switching elements and a plurality of lower arm-side switching elements provided to an inverter for driving a motor; a current determination unit that determines whether a motor current flowing through at least one switching element of the plurality of upper arm-side switching elements and the plurality of lower arm-side switching elements is equal to or smaller than a threshold value; and a short-circuit control unit that performs switching between all-on of the plurality of upper arm-side switching elements and all-on of the plurality of lower arm-side switching elements, on condition that the motor current is equal to or smaller than the threshold value, in a short-circuiting operation of alternately switching all-on of the plurality of upper arm-side switching elements and all-on of the plurality of lower arm-side switching elements.