What does potential free auxiliary contact mean?
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This post was last edited by Yann on 2015-12-2 at 13:25. One potential free auxiliary contact of the emergency stop relay must be connected to the DCS in order to trigger the emergency stop alarm, to put all valves in a fail-safe state, and to disable all motors, including those used in the flaking process. For more details, see the function diagram. What does \"potential free auxiliary contact\" mean here?
Potentially free contacts (also known as “dry contacts”) are simply contacts that are mechanically operated by the main device, but are not electrically connected to it. For example, a motor contactor often has auxiliary contacts that are activated by the main coil and open and close at the same time as the main contacts; however, these auxiliary contacts are not used for controlling the motor starter. If such contacts are connected to an external circuit in order to indicate the status of the starter, without being powered by the motor supply, they are considered potentially free contacts. This type of contact is also referred to as a signal contact. In the case of relays and switches, if the common/terminal is internally connected to a specific voltage level such as 110V phase voltage, then the contact is not potentially free; but if both the common terminal and the normally open (and sometimes also the normally closed) contacts are available for the user to connect to his own system as he sees fit, then such contacts are considered potentially free.