Centrifuge Power Isolation Sequence for Flammable Refrigerants
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Solution Overview
Problem
Refrigerated laboratory centrifuges using flammable refrigerants pose safety risks due to the potential generation of ignition sparks, necessitating enhanced safety measures to prevent ignition during critical operating phases.
Innovation Solution
Implementing a control system that monitors and sequentially switches on electrical components using multiple switches, ensuring reliable detection of operating voltage states to prevent ignition sparks by isolating electrical components from the supply network and monitoring the presence of power supply to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flammable refrigerants like propane or butane are used for cooling, then environmental properties are improved (zero ODP, low GWP), but safety risks increase due to flammability and potential ignition sparks
Solution Approach 1:
The system performs preliminary actions before the refrigeration cycle starts: ventilation fans remove flammable refrigerant from the interior area, and electrical switches ensure complete disconnection of power supply. These preliminary safety measures are executed before any cooling function begins, preventing ignition risks before they can materialize.
Solution Approach 2:
The invention creates a safe operating environment by ventilating the interior area to remove flammable refrigerant concentrations and by ensuring complete electrical isolation during critical phases. This effectively creates an inert or non-ignitable atmosphere in the interior space, allowing the use of flammable refrigerants without compromising safety.
2Object-affected harmful factors
If electrical components are isolated from the supply network using multiple switches, then ignition spark generation is prevented, but device complexity increases
Solution Approach 1:
The electrical isolation system is segmented into multiple independent switches (first switch in L-line, second switch in N-line) that can be controlled independently. This segmentation allows the system to completely disconnect both live and neutral conductors, ensuring no ignition sparks can occur while maintaining manageable complexity through modular switch design.
Solution Approach 2:
The invention introduces intermediary monitoring devices (holding devices) that detect the switching states of the electrical switches and provide feedback to the control system. These intermediaries enable reliable verification of isolation status without adding significant complexity, as they simply monitor and report switch positions rather than actively controlling them.
3Object-affected harmful factors
If ventilation is performed to remove flammable refrigerant before operation, then ignition risk is reduced, but operational time is extended due to additional preparation steps
Solution Approach 1:
Ventilation and electrical isolation are performed as preliminary actions during the start-up sequence before the refrigeration cycle begins. The control system coordinates these safety measures to execute automatically and efficiently, removing flammable refrigerant and isolating electrical components before any cooling function activates, thus preventing ignition risks before they can materialize.
Solution Approach 2:
The ventilation system operates continuously during the start-up phase to ensure complete removal of flammable refrigerant from the interior area. This continuous action, rather than intermittent ventilation, ensures thorough purging of hazardous gases, achieving complete safety while minimizing total preparation time through efficient continuous operation.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a laboratory device (1) with a flammable refrigerant, which has an electrical connection (3) with at least two different electrical potentials for supplying the laboratory device (1) with electrical energy. An electrical switching arrangement (5) has a first electrical switch for electrical isolation from the first potential and a second electrical switch for electrical isolation from the second potential. A sequence control (8) switches on the first electrical switch (SW_L) and, in particular, subsequently the second electrical switch (SW_N). A monitoring device for monitoring the electrical switching arrangement (5) is connected via a first contact on the device side to the first electrical switch (SW_L) and via a second contact on the mains side to an electrical potential different from the first electrical potential.The monitoring device detects an on state of the first electrical switch (SW_L) when an electrical operating voltage is applied between the first contact and the second contact and signals this state to the sequence control (8), which blocks operation of the laboratory device (1) I.) if the first electrical switch (SW_L) is expected to be off, but the monitoring device signals the on state of the first electrical switch (SW_L), or II.) if the first electrical switch (SW_L) is expected to be on, but the monitoring device signals the off state of the first electrical switch (SW_L).