Inverter Short Circuit Fault Management via Random Phase Activation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electrically driven vehicles face difficulties in identifying and addressing short circuit faults in inverters, particularly at low motor rotation speeds, where the back electromotive force is small, leading to challenges in reliably turning on upper and lower arms without phase identification.
Innovation Solution
The vehicle employs a control device that performs a first ON control to turn on upper and lower arms in any arbitrary phase of the inverter when a short circuit fault occurs, and if an abnormality is detected, it cancels the shutdown and performs a second ON control in a different phase, ensuring both arms are turned on without identifying the faulty phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the upper and lower arms in the identified short circuit phase are turned on to suppress overcurrent, then the overcurrent protection is improved, but the reliability of phase identification deteriorates when the motor has low rotation speed and generates small back electromotive force
Solution Approach 1:
Instead of identifying the short circuit phase through normal detection methods that fail at low speeds, the patent inverts the approach by randomly selecting a phase to turn on the upper and lower arms. This random selection method does not depend on back electromotive force magnitude, thereby solving the phase identification reliability problem at low rotation speeds while still achieving overcurrent suppression
2Object-affected harmful factors
If the upper and lower arms in the identified short circuit phase are turned on, then the overcurrent is suppressed, but the inverter may shut down due to detected abnormalities when a short circuit occurs between base and emitter of a transistor element
Solution Approach 1:
The patent replaces the conventional method of turning on arms in the identified short circuit phase with a random phase selection method. This inversion avoids the abnormality detection issue that occurs when attempting to turn on arms in a phase with base-emitter short circuit, thereby maintaining inverter operation continuity while still suppressing overcurrent through random phase activation
3Measurement precision
If phase identification is performed based on motor current input from a current sensor, then the short circuit phase can be identified, but the identification becomes difficult when the motor has low rotation speed and generates small back electromotive force
Solution Approach 1:
The patent extracts the dependency on back electromotive force for phase identification by using random phase selection instead of current-based identification. This removes the constraint that links identification accuracy to motor rotation speed, allowing reliable operation across all speed ranges including very low speeds where back electromotive force is minimal
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 reliably performs the ON control to turn on both upper and lower arms in any phase, effectively managing short circuit faults in the inverter during towing or emergency situations by preventing overcurrent and power line issues.
Implementation Method 1
a back electromotive force generated by the motor during towing of the vehicle
Data Source
AI summary
When ignition is on, a shift position is a neutral position, and shut-down of the inverter is cancelled in a state that a short circuit fault occurs in any phase among multiple phases of the inverter, the electrically driven vehicle performs a first ON control to turn on upper and lower arms in any arbitrary phase among the multiple phases. When an abnormality is detected in the inverter due to the first ON control, the electrically driven vehicle performs a second ON control to turn on upper and lower arms in a different phase from the phase of the first ON control.