Motor Drive Power Conversion with Modular Safety Function Control
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Solution Overview
Problem
The integration of safety modules in power conversion systems for motor control is costly due to the need for long-life components and extensive software development, particularly for achieving functional safety standards like IEC 61508 and IEC 61800-5-2, where hardware-based STO can be sufficient but software-based control is required for SS1, increasing development costs.
Innovation Solution
A power conversion apparatus with a separated control unit and safety function unit configuration, allowing the power conversion apparatus to execute safety functions independently and extend safety functions by attaching a safety module, enabling hardware-based control for STO and software-based control for SS1 through a modular design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a safety module is integrated into the power conversion apparatus to execute safety functions, then safety reliability is improved, but component cost and development cost increase
Solution Approach 1:
The control unit is divided into a basic control unit and a safety function unit that can be independently configured. The safety function unit can be implemented as a separate module or integrated into the basic control unit, allowing flexible configuration based on safety requirements. This segmentation enables the system to achieve necessary safety functions without always requiring a separate safety module, thereby reducing costs while maintaining reliability.
Solution Approach 2:
The basic control unit is designed to potentially incorporate safety function capabilities, making it multi-functional. When safety functions are required, the same control unit can execute both basic control and safety functions, eliminating the need for separate safety modules in many cases. This universal design reduces component count and development costs while maintaining safety reliability.
2Reliability
If long-life components and redundant components are used to reduce failure rate for IEC 61508 certification, then safety reliability is improved, but device complexity and cost increase
Solution Approach 1:
The system dynamically determines whether to execute safety functions based on the configuration and connection status of the safety function unit. The control unit can adapt its operation mode between basic control and safety control, allowing the system to achieve reliability only when needed without permanently increasing device complexity. This dynamic approach enables conditional safety functionality.
3Adaptability or versatility
If software-based control is used to realize safety functions like SS1, then functional flexibility is improved, but development process complexity and cost increase
Solution Approach 1:
The safety function unit is merged with the basic control unit in many configurations, allowing software-based safety functions to be implemented within the existing control software framework. This integration enables the system to achieve functional flexibility for various safety standards (STO, SS1, etc.) without requiring separate safety software development processes, thereby reducing development complexity while maintaining versatility.
Data Source
Figure 1(a)~1(b)
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AI summary
When a power conversion apparatus and safety function unit are integrated, costs of component and development are expensive and the product price increases. A power conversion system includes a power conversion apparatus for driving a motor and a safety function unit for executing a safety function. Upon receiving a safety request signal, the safety function unit outputs a deceleration indication signal to decelerate the motor and outputs a torque-off signal for turning off torque applied to the motor when the motor speed exceeds a predetermined value.