Electric Motor Current Control for Low-Temperature Torque Cancellation
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Solution Overview
Problem
In electric motors, when the winding temperature is below a predetermined level, the rotor's rotation can cause rapid movement of a stationary vehicle, impacting ride comfort and operation stability, as the N and S poles do not initially face each other, leading to unstable torque generation.
Innovation Solution
A control apparatus for electric motors that includes a control part which increases the winding temperature by supplying a d-axis current and generates a q-axis current to counteract the rotation torque, ensuring the N and S poles face each other, thereby stabilizing the vehicle's movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If d-axis current is supplied to increase winding temperature, then the winding temperature increases to activation level, but the rotor rotates rapidly causing poor ride comfort and operation stability
Solution Approach 1:
The control part applies preliminary anti-action by detecting when d-axis current is supplied for heating and automatically generating opposing q-axis current to counteract the rotation torque. This prevents the harmful rotor rotation that would otherwise occur during the temperature increase process, thereby maintaining ride comfort and operation stability while still achieving the necessary winding temperature increase for activation.
Solution Approach 2:
The control part changes current parameters by dynamically adjusting the q-axis current based on the d-axis current magnitude. When d-axis current is supplied for heating, the control part calculates and applies a corresponding q-axis current to generate opposing torque, effectively canceling out the rotation torque and preventing unwanted rotor movement during the heating phase.
2Reliability
If d-axis current is supplied to activate the motor, then the motor can be activated at low temperatures, but the N and S poles misalignment causes rapid vehicle movement
Solution Approach 1:
The control part applies preliminary anti-action by detecting when d-axis current is supplied for heating and automatically generating opposing q-axis current to counteract the rotation torque. This prevents the harmful rotor rotation that would otherwise occur during the temperature increase process, thereby maintaining ride comfort and operation stability while still achieving the necessary winding temperature increase for activation.
Solution Approach 2:
The control part uses feedback by continuously monitoring the d-axis current supply status and using this information to determine when to generate the opposing q-axis current. This feedback mechanism ensures that the counteracting torque is applied precisely when needed during the heating phase, maintaining rotor stability while enabling reliable motor activation at low temperatures.
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 approach improves ride comfort and operation stability by ensuring the vehicle does not move rapidly due to torque cancellation, allowing the electric motor to activate effectively at lower temperatures.
Implementation Method 1
when a d-axis current flows in the state where the N pole generated at the winding and the S pole of the permanent magnet do not face each other, the rotor rotates such that the N pole and the S pole face each other
Implementation Method 2
the control part controls a q-axis current such that a rotation torque with the same magnitude as that of the rotation torque due to the d-axis current in a direction opposite to a direction of the rotation torque due to the d-axis current is generated at the rotor
Data Source
AI summary
A control apparatus for an electric motor that can improve ride comfort and operation stability is provided. The control apparatus includes: a rotor provided with one of a permanent magnet and a winding; and a stator provided with the other of the permanent magnet and the winding. The control apparatus includes a control part. When a temperature of the winding is lower than a predetermined temperature at activation of the electric motor, the control part controls a d-axis current to increase the temperature of the winding. When a rotation torque due to the d-axis current is generated at the rotor, the control part controls a q-axis current such that a rotation torque with the same magnitude as that of the rotation torque due to the d-axis current in a direction opposite to a direction of the rotation torque due to the d-axis current is generated at the rotor.