Motor Control Unit Dynamic Carrier Frequency Adjustment
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Solution Overview
Problem
In motor drive control systems, high temperatures in inverter switching devices can lead to damage due to increased switching losses, especially at high carrier frequencies, which can result in reduced torque and increased vibration, posing a challenge in balancing torque generation and temperature management in smaller, lower heat capacity inverters used in environmentally friendly vehicles.
Innovation Solution
A motor control unit that dynamically adjusts the switching frequency based on the rotation speed and torque requirements, using pre-determined torque limit values to restrict motor operation and manage temperature, thereby reducing switching losses and preventing device damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the carrier frequency is increased to reduce switching operations and suppress temperature rise, then the temperature of the switching device is reduced, but the motor cannot rotate smoothly and vibration increases
Solution Approach 1:
The patent applies dynamics by making the carrier frequency adjustable rather than fixed. The control unit dynamically changes the carrier frequency based on real-time temperature feedback from the switching device. When temperature rises, the carrier frequency is reduced to decrease switching losses and suppress further temperature increase. When temperature is within acceptable range, the carrier frequency is increased to improve motor rotation smoothness and reduce vibration. This dynamic adjustment resolves the contradiction between temperature control and rotation smoothness.
2Stability of the object's composition
If the carrier frequency is increased to improve motor rotation smoothness, then the motor rotates more smoothly, but switching losses increase and temperature rises
Solution Approach 1:
The patent implements feedback control by continuously monitoring the temperature of the switching device and using this information to adjust the carrier frequency. The control unit receives temperature signals from the switching device and automatically modifies the carrier frequency to maintain temperature within safe operating limits while optimizing motor performance. This feedback mechanism ensures that the motor rotates smoothly without causing excessive temperature rise.
3Reliability
If torque is limited to protect switching devices from high temperature, then the switching devices are protected, but the torque output is reduced
Solution Approach 1:
The patent changes the parameter being controlled from torque limitation to carrier frequency adjustment. Instead of limiting torque to protect switching devices, the system adjusts the carrier frequency to control switching losses and temperature. This parameter change allows the motor to maintain full torque output while protecting switching devices through thermal management via frequency modulation, thereby resolving the contradiction between device protection and torque output.
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 allows for maximum torque generation while effectively suppressing temperature rises in switching devices, ensuring the motor operates smoothly and preventing damage, even at high carrier frequencies.
Implementation Method 1
a sharp rise in temperature is likely to occur due to heat concentration. This temperature rise is particularly apparent at high carrier frequencies where switching is frequently performed.
Implementation Method 2
By decreasing the carrier frequency instead of limiting the torque, the number of switching operations can be reduced. Thus, switching loss can be reduced, thereby suppressing the temperature rise by an amount that corresponds to the reduction in the switching loss.
Data Source
AI summary
A motor unit and a vehicle equipped with the unit according to the invention includes a control unit that selects a switching frequency, that is, a carrier frequency, in accordance with a rotation speed of the motor and a torque required from a motor. When an inverter temperature becomes high, the control unit limits the torque of the motor to suppress further increase in the inverter temperature. A limit value used in restricted operation is determined in accordance with the temperature and the carrier frequency of the inverter.