Motor Control Unit for Three-Phase Battery Heating Balance
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Solution Overview
Problem
Existing electric vehicle battery heating solutions, such as using a PTC resistor or motor winding heat, either increase costs and space or result in uneven heating, affecting motor performance and reducing battery discharge efficiency at low temperatures.
Innovation Solution
A motor control unit with an inverter circuit and controller that simultaneously outputs currents to three phases of motor windings, ensuring they reach a preset current sequentially, thereby achieving even heating and maximizing heating power without additional heating apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a PTC resistor is added to heat the power battery pack, then the heating function is improved, but the device complexity and cost increase
Solution Approach 1:
The motor windings are made to serve dual functions: motor operation and battery heating. By controlling the inverter circuit to output currents to all three phases of motor windings, the windings generate heat that is transferred to the power battery pack, eliminating the need for a separate PTC resistor heating apparatus
Solution Approach 2:
The motor windings generate heat through their own resistance when current flows through them during motor operation. This self-generated heat is then transferred to the power battery pack via the cooling medium circulation system, allowing the motor components to serve the heating function without external heating devices
2Device complexity
If motor winding heat is used to heat the power battery pack, then the device complexity is reduced, but the heating power is insufficient and heating speed is slow
Solution Approach 1:
The controller continuously controls the inverter circuit to output currents to all three phases of motor windings, ensuring continuous heat generation. The cooling medium circulation system also operates continuously to transfer heat from the motor windings to the power battery pack, maintaining sustained heating power
Solution Approach 2:
The controller adjusts the current parameters flowing through the motor windings to optimize heat generation. By controlling the magnitude and duration of currents in all three phases, the system maximizes the heating power output from the motor windings while maintaining balanced thermal distribution
3Temperature
If current is injected into motor windings for heating, then the heating function is achieved, but the three phases generate heat unevenly causing motor imbalance
Solution Approach 1:
The controller applies different current control strategies to each phase of motor windings based on their individual temperature states. By monitoring and adjusting the current in each phase separately, the system ensures uniform heat distribution across all windings, preventing localized overheating and maintaining motor balance
Solution Approach 2:
The controller intentionally creates asymmetric current distribution among the three phases during different time periods. By rotating which phase receives higher current in a cyclic manner, the system achieves symmetric thermal distribution across all phases over time, preventing permanent imbalance while maximizing overall heating efficiency
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
Even heating of motor windings increases overall heating power, enhances motor symmetry and reliability, and reduces costs by eliminating the need for extra heating components.
Implementation Method 1
Waste heat generated by a motor winding is absorbed by using a heat-conducting medium
Implementation Method 2
Waste heat generated by a motor winding is absorbed by using a heat-conducting medium
Data Source
AI summary
This application discloses a motor control unit, a power train, a control method, and an electric vehicle, and relates to the field of electric vehicle technologies. An input end of the motor control unit connects to a power battery pack, an output end of the motor control unit connects to three phases of motor windings of a motor, and the motor control unit includes an inverter circuit and a controller. The controller is configured to control the inverter circuit to simultaneously output currents to the three phases of motor windings, and control the currents input to all the phases of motor windings to sequentially reach a preset current.