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Can apply the power supply 24V, 5A for PLC S71200 DC DC DC ?

Created by: luuthienchinh at: 9/14/2018 11:04 AM (5 Replies)

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9/14/2018 11:04 AM	Rate (0)
luuthienchinh Posts: 1 Rating: (0)	Dear sir, With the maximum 12A inrush current at 28.8V Can we apply the power suppy 24V, 5A for PLC S71200 DC DC DC ? ------------------------------------------------------------------------------------------ Split from Power consumption of CPU 1214C .
luuthienchinh Posts: 1 Rating: (0)	Last edited by: Jen_Moderator at: 9/14/2018 11:42:38 AM New subject after splitting
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9/14/2018 11:24 AM	Rate (0)
Ste39 Platinum Member Joined: 1/21/2013 Last visit: 10/31/2022 Posts: 4617 Rating: (700)	luuthienchinh Dear sir, With the maximum 12A inrush current at 28.8V Can we apply the power suppy 24V, 5A for PLC S71200 DC DC DC ? Hello, Yes, no problem Single-phase, 24 V DC (for S7-1200) - Industry Mall - Siemens WW

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9/14/2018 12:12 PM	Rate (0)
#dP Posts: 2826 Rating: (658)	Hello. Ste39 luuthienchinh Dear sir, With the maximum 12A inrush current at 28.8V Can we apply the power suppy 24V, 5A for PLC S71200 DC DC DC ? Hello, Yes, no problem Single-phase, 24 V DC (for S7-1200) - Industry Mall - Siemens WW I have never noticed that specification before. 12A@28.8V inrush.. wow! We have never had any issues before, even if we do not use Siemens PSUs. @Ste39 - Where in the specification (the link) does it mention the inrush (output of PSU) can be handled? Regards.
#dP Posts: 2826 Rating: (658)	Last edited by: #dP at: 9/14/2018 12:12:45 PM
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9/14/2018 12:21 PM	Rate (0)
Ste39 Platinum Member Joined: 1/21/2013 Last visit: 10/31/2022 Posts: 4617 Rating: (700)	#dP Hello. Ste39 luuthienchinh Dear sir, With the maximum 12A inrush current at 28.8V Can we apply the power suppy 24V, 5A for PLC S71200 DC DC DC ? Hello, Yes, no problem Single-phase, 24 V DC (for S7-1200) - Industry Mall - Siemens WW @Ste39 - Where in the specification (the link) does it mention the inrush (output of PSU) can be handled? Regards. Hello #dP, in fact, I posted to him this PSU that for a CPU 1200 is enough even with 2.5A

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9/14/2018 12:51 PM	Rate (0)
#dP Posts: 2826 Rating: (658)	Okay. Please allow me the attempt to reply to the 'inrush' question. Modern PSUs (power supply units) are designed to handle even short-circuits. The power output from the PSU is reduced when the demand is too high for too long. The theoretical inrush specified for the PLC would be controlled / throttled by PSU. The PLC can still switch on even if the current to the PLC does not reach the inrush current value. The important thing is that the switch on current is controlled. The specification of the PSU needs to keep in mind the requirements of the whole circuit. The devices pulling from the PSU could easily be more than the PLC; the mere numbers can contribute strongly. Having a too big PSU is also dangerous. A 24V/20A PSU could easily push enough power into a short circuit that cables may be damaged. It is best design to break up the design into smaller portions where each is protected. A 24V/2A fuse would work for example. Here the potential inrush plays a role; best to not have a too quick reaction fuse. @Ste39, please amend the above as from your own knowledge. It should be most welcome for the topic starter. ~
#dP Posts: 2826 Rating: (658)
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9/17/2018 4:38 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/26/2023 Posts: 13079 Rating: (2121)	Last year I had a different story with a contactor pulling in crow-baring the PSU, cycling the 24V system long enough for the PLC to shut down, and then restart. That contactor had an in-rush of 28A, with steady state / holding current of just under 0.5A. It switches up to 400A circuits. My 10A P/S failed miserably. I paralleled a 2nd Siemens 10A supply and they held against the 28A in-rush just fine. The next version of that system had a 20A supply and it worked just fine even with that large in-rush. It was quite fun watching it (knowing it would not hurt anything), but not fun for my customer. #dP Okay. Please allow me the attempt to reply to the 'inrush' question. Modern PSUs (power supply units) are designed to handle even short-circuits. The power output from the PSU is reduced when the demand is too high for too long. The theoretical inrush specified for the PLC would be controlled / throttled by PSU. The PLC can still switch on even if the current to the PLC does not reach the inrush current value. The important thing is that the switch on current is controlled. The specification of the PSU needs to keep in mind the requirements of the whole circuit. The devices pulling from the PSU could easily be more than the PLC; the mere numbers can contribute strongly. Having a too big PSU is also dangerous. A 24V/20A PSU could easily push enough power into a short circuit that cables may be damaged. It is best design to break up the design into smaller portions where each is protected. A 24V/2A fuse would work for example. Here the potential inrush plays a role; best to not have a too quick reaction fuse. @Ste39, please amend the above as from your own knowledge. It should be most welcome for the topic starter. ~
	science guy
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