Motor Inverter Fail-Safe Control With Dynamic Speed Thresholds
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Solution Overview
Problem
Existing motor inverter devices rely on fixed speed thresholds for fail-safe control, leading to excessive execution of fail-safe control even when it is not necessary, potentially causing damage to the power source and motor due to overcharging and brake torque generation.
Innovation Solution
The inverter device calculates dynamic minimum and maximum speeds based on power source voltage, correction coefficients, and offset values specific to the motor and power source, allowing for adaptive fail-safe control activation and deactivation, thereby narrowing the speed range for fail-safe control execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed speed threshold is used for fail-safe control, then the control logic is simple, but the fail-safe control is excessively executed even when not necessary
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed speed threshold to a dynamic speed threshold that varies with motor operating conditions. The controller calculates a dynamic speed threshold based on real-time parameters including motor speed, acceleration, and temperature, allowing the fail-safe control activation speed to adapt to different operating states. This resolves the contradiction by making the control logic more complex but significantly more accurate in determining when fail-safe control is actually needed.
Solution Approach 2:
The patent changes the parameter used for fail-safe control decision-making from a single fixed speed value to multiple varying parameters including motor speed, acceleration rate, and stator coil temperature. By calculating the dynamic speed threshold as a function of these parameters, the system achieves more precise control activation that matches actual safety needs, reducing unnecessary executions while maintaining reliability.
2Reliability
If fail-safe control is executed at high speeds, then protection against overcharging and IGBT damage is provided, but unnecessary brake torque is generated when abnormality is not present
Solution Approach 1:
The patent makes the fail-safe control activation dynamic by calculating a speed threshold that adapts to current motor operating conditions including acceleration rate and temperature. This dynamic threshold ensures that fail-safe control with brake torque is only activated when both high speed and actual abnormality conditions are present, preventing unnecessary brake torque generation while maintaining protection when needed.
Solution Approach 2:
The patent implements feedback mechanisms by continuously monitoring motor speed, acceleration, and temperature, then using this feedback to dynamically adjust the speed threshold for fail-safe control activation. This closed-loop approach ensures that brake torque is applied only when the dynamic threshold indicates both high speed and abnormal operating conditions, eliminating unnecessary harmful brake torque while preserving essential protection.
3Object-generated harmful factors
If the speed threshold is set low to avoid excessive fail-safe control, then unnecessary brake torque is reduced, but the risk of overcharging and IGBT damage increases
Solution Approach 1:
The patent changes the speed threshold from a static low value to a dynamic value that incorporates multiple parameters including motor speed, acceleration rate, and temperature. This allows the system to maintain a lower effective threshold in normal conditions to avoid unnecessary brake torque, while automatically raising the threshold when abnormality indicators are present, thus preventing both excessive brake torque and protection failures.
Solution Approach 2:
The patent applies preliminary action by pre-calculating the dynamic speed threshold based on current operating conditions before fail-safe control is needed. This allows the system to be prepared with the appropriate activation threshold in advance, ensuring that when high speed is reached, the decision to apply brake torque is immediate and accurate, preventing both unnecessary torque and protection failures.
Data Source
AI summary
An inverter device is provided. The inverter device converts power from a power source and drives a motor. The inverter device includes an inverter circuit having a switch, a driver circuit that switches the switch on and off, and a controller that controls the driver circuit. The controller has a speed calculator used to calculate a minimum speed of the motor based on a power source voltage. After the controller performs fail-safe control, when a speed of the motor is less than the minimum speed, the fail-safe control is ended.