EV Safety Charging System Detecting Rotor Movement via Current Imbalance

Solution Overview

Problem

During high-speed charging of electric vehicles, design deviations and current sensor failures can cause the rotor of the motor to move, leading to unsafe vehicle movement due to uneven three-phase currents, which existing systems fail to detect reliably without position sensors.

Innovation Solution

A safety charging system that includes a current variation amount sensor and a controller to monitor the difference in three-phase currents flowing through the motor coil, interrupting the charging process when the current variation exceeds a reference value, using PWM control to prevent rotor movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the motor and inverter operate as a booster converter to boost charging voltage, then charging speed is improved, but the rotor may move due to design deviation or sensor failure causing unsafe vehicle movement

Engineering Contradiction:

Improvecharging speedVSAvoidvehicle stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system continuously monitors three-phase current values during charging and uses this feedback to detect rotor movement. When current imbalance exceeds a threshold, the controller interrupts charging, creating a closed-loop safety mechanism that maintains vehicle stability while enabling high-speed charging

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent uses three-phase current values as an intermediary indicator to indirectly detect rotor movement. Instead of directly sensing rotor position, the system measures current balance across phases, where current imbalance serves as a mediator signal that triggers safety intervention

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If position sensor is used to detect rotor movement, then detection reliability is improved, but system complexity and cost increase

Engineering Contradiction:

Improvedetection accuracyVSAvoidsensor system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses three-phase current values as an intermediary indicator to indirectly detect rotor movement. Instead of directly sensing rotor position, the system measures current balance across phases, where current imbalance serves as a mediator signal that triggers safety intervention

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces mechanical/physical position sensors with an electrical measurement approach. By monitoring current balance in the three-phase system, the patent substitutes direct mechanical rotor position detection with an electrical field-based indirect measurement method

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If current sensor fails or has error, then manufacturing cost is reduced, but detection precision of rotor movement deteriorates

Engineering Contradiction:

Improvesystem costVSAvoidcurrent measurement accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The system applies local quality analysis by examining the distribution pattern of three-phase currents rather than relying on a single absolute measurement. By comparing relative current balance across phases, the system can detect rotor movement through local imbalances even when absolute current sensor accuracy is limited

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system continuously monitors three-phase current values during charging and uses this feedback to detect rotor movement. When current imbalance exceeds a threshold, the controller interrupts charging, creating a closed-loop safety mechanism that maintains vehicle stability while enabling high-speed charging

Inventive Principle:

Principle #23Feedback

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

Effectively prevents safety accidents by reliably detecting rotor movement and interrupting the charging process, ensuring the vehicle remains stationary during charging.

Implementation Method 1

three-phase currents Ia, Ib, and Ic flow in a motor coil through a pulse width modulation (PWM) control method to generate three-phase forces (torque) moving a rotor

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11456603B2Safety charging system for electric vehicle and safety charging method therefor

Publication Date: 2022.09.27 HYUNDAI MOTOR CO LTD

AI summary

A safety charging system includes: a motor and an inverter which boost a voltage charged from a high-speed battery charger to a high voltage battery; a current variation amount sensor configured to detect variation amount of a current flowing in a motor coil from the high-speed battery charger; and a controller configured to determine that a rotor of the motor rotates when the variation amount of the current detected in the current variation amount sensor is greater than a reference value and perform control of interrupting a charging process.