2TLC172316M0201, rev E
6
www.abb.com/ jokabsafety
2015-09-30
3 Function
description
Safety level
The BT50(T) has a double and supervised internal safety function. Power failure, internal component faults or
external interference cannot result in dangerous functions.
Input via A1 on its own is not protected from short circuiting, and therefore installation is critical for the safety level
to be achieved. To achieve a higher safety level a cable shielded with earth connection can be used at both A1 and
A2 (See the connection examples in section 4.) The higher safety level is achieved by fault exclusion at the cables
to the A1 and A2 connections, through shielded cables with earth connection or cables protected against damage,
e.g. by cable ducting, armouring. The cables connected between connections X4 and A1 need the same protection
if installed outside the cabinet. For further information see Table D4 IEC 13849-2:2012.
Steering input only via A2 is only allowed with the failsafe transistor outputs from Pluto PLC.
Internal block diagram
When supply voltage is connected to A1, A2 and X4, relays K1 and K2 are activated. K1 and K2 drop if the supply
voltage is disconnected. Both relays K1 and K2 must drop for them to be activated again. The test circuit, A1 – X4,
must be closed for the outputs to be activated.. Thereafter A1 – X4 can either be open or constantly closed.
The supervising circuit ensures that both K1 and K2 have dropped before they can be reactivated. The stop
function complies with the requirement that a component fault or external interference cannot lead to a dangerous
function.
The safety outputs consist of contacts from K1 and K2 connected internally in series across terminals 13 – 14, 23 –
24, and 33 – 34. These contacts are used to cut the power to components which stop or prevent hazardous
movements/functions. It is recommended that all switched loads are adequately suppressed and fused in order to
provide additional protection for the safety contacts.
The NC output 41 – 42 should only be used for monitoring purposes e. g. indication lamp for emergency stop
pressed. The BT50T is the same as BT50 except that it also has delay time selectable outputs and additional
information output relay. This is explained in the following connection diagrams.
BT50T – Information output
BT50T – Delay times
