Rotary Electric Machine Control Device Torque Limiting
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Solution Overview
Problem
In rotary electric machines, electrical resonance occurs when a conversion operation abnormality happens in the DC voltage converter, leading to excessive drive or output currents, especially at high rotation speeds, due to the use of downsized capacitors aimed at reducing size, but not adequately addressing the resonance issue.
Innovation Solution
A control device is implemented that includes torque limit control and rotation speed reduction mechanisms when a conversion operation abnormality is detected, specifically setting a predetermined rotation speed threshold to prevent electrical resonance by limiting output torque or reducing rotation speed when the machine exceeds this threshold, corresponding to the lower limit frequency range where resonance is likely to occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a downsized capacitor with minimum necessary capacitance is used in the DC voltage converter, then the device size is reduced, but electrical resonance occurs at high rotation speeds when conversion operation abnormality occurs
Solution Approach 1:
The patent changes the operational parameters by introducing a rotation speed threshold that corresponds to the lower limit frequency of the resonance-prone frequency range. When the rotation speed exceeds this threshold and conversion operation abnormality is detected, the control device executes torque limit control or rotation speed reduction control, thereby changing the operating conditions to avoid the resonance frequency range and preventing electrical resonance while maintaining the use of downsized capacitors
2Reliability
If torque limit control or rotation speed reduction control is executed to prevent electrical resonance, then current is maintained within appropriate ranges, but the rotary electric machine cannot operate at high rotation speeds
Solution Approach 1:
The patent implements dynamic control by continuously monitoring both the rotation speed and the operation state of the DC voltage converter. The control strategy adapts in real-time: when conversion operation abnormality is detected and rotation speed exceeds the predetermined threshold, torque limit control or rotation speed reduction control is executed; when abnormality is resolved or speed is below threshold, normal operation is restored. This dynamic approach allows the system to operate at high speeds under normal conditions while preventing resonance only when necessary
Data Source
AI summary
A control device of a rotary electric machine capable of preventing occurrence of electrical resonance when a conversion operation abnormality of a DC voltage converter occurs is provided. In a case that the DC voltage converter stops a conversion operation and the conversion operation abnormality that input/output voltages become equal occurs, when a vehicle speed proportional to an electric motor rotation number exceeds a torque limit start vehicle speed, i.e., when the electric motor rotation number exceeds a torque limit start rotation number, a torque limit control for limiting an output torque of the electric motor is executed. The torque limit start vehicle speed is set to a vehicle speed corresponding to a lower limit frequency of a predetermined frequency range where there is a high likelihood of an electrical resonance occurring in the DC voltage converter when the conversion operation abnormality occurs.