Stationary EV Motor Heating via D-Axis Current Losses
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Solution Overview
Problem
Electric vehicles lack a viable method to heat the passenger compartment and vehicle battery when stationary, as the electric motor does not generate waste heat in this state.
Innovation Solution
A method utilizing a pulse-controlled inverter and coolant circuit to generate heat loss in a three-phase electric motor by controlling d-axis currents, even when the motor is stationary, allowing this heat to be used for heating through a heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the electric motor is kept stationary to avoid unnecessary energy consumption, then energy efficiency is improved, but the ability to generate waste heat for heating the passenger compartment and vehicle battery is lost
Solution Approach 1:
The patent converts the harmful effect of electrical losses (I²R heating) in the motor windings, which normally represent energy waste, into a beneficial heat source for heating the passenger compartment and vehicle battery. By controlling d-axis current specifically for heating purposes, the patent transforms what would be pure energy loss into useful thermal energy, resolving the contradiction between energy efficiency and heating capability.
Solution Approach 2:
The electric motor is made multi-functional by enabling it to serve both as a propulsion device during driving and as a heat generation device when stationary. The control system switches the motor's function based on operational requirements, allowing the same hardware to fulfill multiple roles and eliminate the need for separate heating systems.
2Temperature
If d-axis current is controlled to generate heat loss in the electric motor when stationary, then heating capability is improved, but energy consumption increases
Solution Approach 1:
The patent accepts controlled energy consumption as d-axis current to generate heat, but reframes this consumption as productive rather than wasteful. The electrical energy that would otherwise be completely lost is converted into useful heat for the passenger compartment and battery, making the energy consumption purposeful and beneficial rather than harmful.
3Temperature
If the electric motor and inverter are used as heat sources when stationary, then heating capability is improved, but device complexity increases due to additional control requirements
Solution Approach 1:
The existing pulse-controlled inverter and motor control system are made multi-functional by adding heating capability to their existing propulsion function. The same control hardware and software infrastructure is utilized for both driving and heating operations, avoiding the need for separate dedicated heating control systems and minimizing additional complexity.
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
Enables effective heating of the passenger compartment and vehicle battery when the vehicle is stationary by converting electrical energy into heat without propelling the vehicle, utilizing heat loss from the electric motor and inverter.
Implementation Method 1
a positive d current and/or negative d current is controlled in a d-axis, with the result that heat loss is generated
Implementation Method 2
a coolant circuit for cooling the electric motor and the pulse-controlled inverter using coolant
Implementation Method 3
the coolant circuit using the coolant to supply heat to a heat exchanger for heating a passenger compartment and/or a vehicle battery
Data Source
AI summary
A method for heating a motor vehicle having a three-phase electric motor as a traction motor includes providing a pulse-controlled inverter for supplying power to the electric motor and providing a coolant circuit for cooling the electric motor and the pulse-controlled inverter using coolant, the coolant circuit using the coolant to supply heat to a heat exchanger for heating a passenger compartment and/or a vehicle battery, wherein when the electric motor is stationary, a positive d current and/or negative d current is controlled in a d-axis, with the result that heat loss is generated, the heat loss being introduced into the coolant.