继电器是保护系统的逻辑元件，它感知故障，并使断路器解扣电路带电和断路器打开触点。

Relays are the logic elements of a protection system which sense the fault and cause the circuit-breaker trip circuits to be energized and the breakers to open their contacts.

youdao

针对数控设备的限位保护功能有些欠缺，容易发生超程故障等问题，提出采用把所有限位保护电路改为负逻辑控制，并对这一方案进行了理论分析和实践。

As for the above-mentioned problems, the research puts forward to turn all circuit protection into negative logic control and has carried out theory analysis and practice.

youdao