Soft Starter With Separate Safety Signal Input
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Solution Overview
Problem
Existing soft starters for electric motors lack a high degree of safety and compactness, requiring additional components to achieve safety integrity levels, which increases complexity and costs.
Innovation Solution
A soft starter design with a bypass circuit featuring a semiconductor switch and an electromagnetic switch, controlled by a unit that receives and verifies safety and operational signals, allowing for safe operation and reduced component count, achieving SIL 2 safety integrity without additional contactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional contactors are used to achieve high safety integrity levels, then safety is improved, but device complexity and component count increase
Solution Approach 1:
The patent combines the safety function and operational control function into a single contactor unit. The contactor integrates both safety-related switching operations and normal operational switching operations, eliminating the need for separate contactors for each function. This merging reduces component count while maintaining the required safety integrity levels through the unified control unit's ability to handle both signal types.
Solution Approach 2:
The control unit is designed with universal functionality to process both safety signals and operational control signals through a single interface. The contactor unit serves multiple purposes: it responds to safety signals for emergency stopping, processes operational commands for motor control, and provides unified status feedback. This multi-functionality allows one component to replace what would traditionally require multiple specialized components.
2Device complexity
If a unified control unit handles both safety and operational signals, then device complexity is reduced, but safety signal reliability may be compromised
Solution Approach 1:
Within the unified control unit, the patent implements segmentation by providing separate signal inputs: a dedicated safety signal input specifically for safety-related signals and a separate operational control signal input for normal operations. This internal segmentation ensures that safety signals are processed through a dedicated pathway within the unified unit, maintaining their reliability while still benefiting from the overall simplification of using a single control unit rather than multiple separate components.
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
The solution provides a high degree of safety and compactness, achieving SIL 2 safety integrity with reduced components, ensuring safe operation of electric motors and simplifying integration into existing systems.
Implementation Method 1
The semiconductor switch is designed, for example, as anti-parallel thyristors, which are suitable for enabling arc-free switching
Implementation Method 2
An electromagnetic switch, for example a relay, is fitted parallel to the semiconductor switch
Data Source
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AI summary
The invention relates to a soft starter (10) for connecting at least one main circuit (12, 14, 16), each of which includes a bypass circuit (20) having a semiconductor switch (22). Said soft starter (10) comprises a control unit (40) for actuating the bypass circuit (20), and the control unit (40) is equipped with a control signal input (44). According to the invention, the control unit (40) has a separate safety signal input (42).