رله siemens مدل 3TK2827-1AB20

رله حفاظتی وسیله ای است که برای محافظت از دستگاه های برقی که در اثر تغییر کمیت های الکتریکی یا فیزیکی تحریک می شود و موجب به کار افتادن دستگاه ها و تجهیزات معینی میگردد و دستگاه معیوب را از شبکه خارج می سازد.
به عبارت دیگر وظیفه به وسیله رله حفاظتی محل وقوع عیب از شبکه جداسازی می شود و سایر قسمت های سالم شبکه به کار خود ادامه می دهند و ثبات و پایداری شبکه حفظ می شود.

manual start
For a manual start, an enable signal is generated when the ON button is pressed. This function is also designated as static operation and is specified for EMERGENCY STOP devices (EN 60204-1, conscious action). Safety relays with automatic start can be used up to Category 3: The feedback circuit is statically monitored.
monitored start
For a monitored start, an enable signal is generated when the ON button is pressed. This function is also designated as static operation and is specified for EMERGENCY STOP devices (EN 60204-1, conscious action). Possible with safety relays up to Category 4: The feedback circuit is dynamically monitored.
automatic start
For an automatic start, an enable signal is generated without a manual agreement. This function is also designated as dynamic operation and is not permissible for E Stop devices.
cascading (cascading input)
Safety-relevant single-channel input of a safety relay that is internally evaluated just the same as a sensor signal: Logically AND'ed with other signal encoder inputs. If a voltage is not present, the safety relay safely shuts down the enable circuit (outputs). Operational switching: Depending on the particular safety relay, the enable circuits are switched with a monitored or an autostart (refer to the Safety Navigator 3TK28 in the Attachment)
categories acc. to EN 954-1
Categories B, 1, 2, 3 and 4 are described in EN 954-1:1999 (harmonized Standard in the Machinery Directive): The higher the Category, the higher the fault detection.