Emerson Exchange 365

• Not Answered

M-Series System Power Supply

Hi Forum Members,

In the DeltaV Power and Grounding Manual Aug 2023 Section 4.3.3, there is a note regarding power supply feed to M-Series System Power supplies that says, "Emerson recommends using 24 VDC bulk power supply feeds to the DeltaV hardware for all new or upgraded installations."

I'd like to know why it is recommended to use 24VDC Power Supply feeds to the M-Series System Power Supply instead of 12VDC Power Supply feeds.

Rishi

• 4 Dec 2024 8:58 AM
• Cancel

2 Replies

• KeithStThomas

  

  • 4 Dec 2024 3:11 PM

  We need 24VDC power for the transmitter field wiring anyway, so we opted to use 2 x 24VDC bulk power supplies in a redundant arrangement. This saves us from having to buy both the 12VDC and 24VDC power supplies.

  • Cancel
• Andre Dicaire

  

  • 4 Dec 2024 4:30 PM

  There is a history behind that statement. Two main factors are that the older 24 VDC supplies did not provide as much 12VDC power as the newer models, which can drive up to 8 amps down the IO bus. Considering the Carriers are rated to a max of 8 Amps, (goes way back to v10 time frame when S-series was released). Using 24 VDC bulk prevents exceeding this carrier limit with installation of too many IO cards, without injecting new 12 VDC power. Note that with 12 VDC bulk, you still are required to calculate and design the IO bus so as not to exceed the Carrier limit, which the 12 VDC bulks can exceed if too many cards or installed on a single feed.
  
  In the S-series, we chose only go with a 24 VDC bulk supply design to simplify design choices. The 12 VDC bulk connection option was therefore removed. The DC/DC system power supplies for M-series can still receive a 12VDC bulk source, but given that design is focused solely on 24 VDC moving forward, your lifecycle planning should be considering a move to 24 VDC at some point as your existing 12 VDC bulk supplies reach the end of their service life.
  
  Note that PK, EIOC, SZ, CSLS, CIOC are all solely 24VDC and as Rishi points out, field power is 24VDC, 12 VDC bulk supplies should not be used in new builds and should be phased out when appropriate.

  Andre Dicaire

  • Cancel