Potential contacts versus potential free contacts usage in control circuits

  • Thread starter Senthil Kumar K, Sr.Manager/IPP/C&I
  • Start date

Thread Starter

Senthil Kumar K, Sr.Manager/IPP/C&I

Dear list members.

I feel very happy to be a part of global instrument engineers community.

My first question

Normally in control circuits we are using potential free contacts for controlling purposes from DCS. But some of our customers are prefering
230V AC potential contacts. Can anyone Please explain the merits and demerits of using potential contacts inplace of potential free contacts.

your question is not clear. Even in potential free contacts, the interrogation voltage will be from the receiving device. In potential
contact, the interrogation voltage is supplied by "from" device i.e, source deveice.

we can discuss about if the question is more elaborative.

Potential free are better. With potential free, you supply the control voltage. You are not limited by the provider of the signal. You also avoid problems with common voltage; where your 24VDC return is 5 volts higher or lower than the other system power supply.
Well it depends on the requirement of the user.

If the user is sure he needs 230 volts supply for his devices, then you can provide it hard wired to a 230 volts source. If you provide hard wired contacts with a source, you need to know the current requirement (amp) in advance, so that the devices do not draw more than your source can feed.

BUT it is always BETTER to provide Potential FREE contacts, for a simple reason that, there is a greater flexibility for user to use potn free contacts. It is generic in nature.

For example:- If the user wants to use groups of 3 relays to be powered from RYB lines of his source, it is simple for him to wire this kind of setup, if it is a series potential free contacts terminated on a terminal strip.