PWM Carrier Frequency Switching for Stable Motor Torque Control
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Solution Overview
Problem
Existing motor control devices face challenges in preventing response deterioration and torque fluctuations when switching carrier frequencies, leading to instability and vibration in motor operations across a wide operating range.
Innovation Solution
A motor control device with a PWM control unit, a carrier frequency setting unit, and a carrier frequency switching calculation unit that adjusts the frequency switching speed based on the torque command value change rate, allowing for stable motor operation by optimizing carrier frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the carrier frequency is suddenly switched, then the inverter is protected from overheating, but torque fluctuation called switching shock occurs
Solution Approach 1:
The patent applies preliminary action by calculating and preparing the frequency switching speed before actually switching the carrier frequency. The control device determines the appropriate switching speed based on current operating conditions, then executes the frequency transition smoothly over time. This prevents sudden torque fluctuations while still achieving the thermal protection goal by transitioning to a safer carrier frequency.
Solution Approach 2:
The patent makes the frequency switching process dynamic by adjusting the switching speed according to motor operation information. Rather than abrupt frequency changes, the system dynamically controls the rate of frequency transition, and this dynamic approach suppresses torque fluctuations while maintaining effective thermal management.
2Temperature
If the carrier frequency is switched, then thermal protection is achieved, but response frequency deterioration occurs
Solution Approach 1:
The patent applies preliminary action by calculating the frequency switching speed in advance based on motor operation information before executing the carrier frequency switch. This pre-calculation ensures that the switching process maintains appropriate response characteristics, preventing response frequency deterioration while achieving thermal protection.
Solution Approach 2:
The patent uses feedback by continuously monitoring motor operation information (rotation speed, torque, temperature) and using this information to adjust the frequency switching speed. This feedback mechanism ensures that response frequency requirements are maintained while still achieving effective thermal protection through carrier frequency switching.
3Speed
If the carrier frequency is preset according to rotation speed, then the response frequency is maintained, but torque fluctuation occurs during switching
Solution Approach 1:
The patent applies dynamics by making the frequency switching speed adaptive rather than fixed. Even though carrier frequency is preset according to rotation speed, the actual switching process dynamically adjusts the transition speed based on real-time motor operation information, thereby maintaining response frequency while suppressing torque fluctuations during the transition.
Solution Approach 2:
The patent changes the switching behavior by introducing frequency switching speed as a controllable parameter. While the target carrier frequency is preset based on rotation speed, the rate of transition is dynamically adjusted, optimizing both response frequency maintenance and torque stability during the switching process.
Data Source
AI summary
A motor control device includes a PWM control unit, a carrier frequency setting unit, and a carrier frequency switching calculation unit. The PWM unite generates a signal to drive an inverter by pulse width modulation. The carrier frequency setting unit sets a carrier frequency used for pulse width modulation according to a number of rotations of a motor. The carrier frequency switching calculation unit calculates a frequency switching speed of the carrier frequency and is configured to perform a calculation method. The calculation method includes setting at least one of an emergency mode, a response priority mode, or a fluctuation suppression priority mode in response to various operating conditions.