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Power Consumption

5/16/2008 10:54 PM	Rate (0)
Sohail Posts: 5 Rating: (0)	Dear All, how i calculate the power comsumption of each PLC input/out module installed in the rack?what r the factors need to take in consideration when going to select the PS for racks? Awaiting for response Thanks
Sohail Posts: 5 Rating: (0)
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5/19/2008 5:49 PM	Rate (0)
Denilson Pegaia Diamond Member Joined: 9/23/2005 Last visit: 12/24/2025 Posts: 4434 Rating: (1487)	Sohail Dear All, how i calculate the power comsumption of each PLC input/out module installed in the rack?what r the factors need to take in consideration when going to select the PS for racks? Awaiting for response Thanks Hi, if you take a look at the ST70 catalog (www.siemens.com/simatic/printmaterial) you can see that for each module has a current consumption from load voltage L+ (for external PS consumption calculation) and a current consumption from backplane bus DC 5 V (for S7-400PS consumption calculation).
	Denilson Pegaia Siemens Industry Sector Technical Support
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This contribution was helpful to 1 thankful Users H2sh

5/20/2008 7:22 AM	Rate (0)
Aret Posts: 2348 Rating: (265)	Please mention, that all IO signals would consume power too (from 24V).
Aret Posts: 2348 Rating: (265)
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6/27/2008 5:10 PM	Rate (0)
AVSR Posts: 12 Rating: (0)	We can design in different ways, simplest way is, use rack PS for modules' back plane and for I/O from field use seperate PS. To Calculate Rack PSadd the power consumption of each module at 5v backplane, which is available in tecnical spec of every module. To calculate Field I/O PS, add the wattage of all the field equipmets.
AVSR Posts: 12 Rating: (0)
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7/1/2008 6:15 PM	Rate (0)
Dorftrottel? Silver Member Joined: 8/10/2006 Last visit: 12/4/2025 Posts: 298 Rating: (29)	Power budgets can be a fun one to calculate (yeah, right). I presume you are doing this for proper sizing of your DC power supply in the cabinet. There's the power for the profibus interface module. If it's a ET200M type, as you add modules, they consume more power. Quiescent power + power consumed by each module\ Per Module: Quiescent Power + Power per point. If you are using modules with diagnostic capabilities (digital in or digital out) they also consume power for the diagnostic function. Know the power consumption of your devices. We've been surprised by the consumption of different field devices, compared to the listed currents. Finally, recommend doing a power test where you measure the current consumption with the system active. Based on my experience, your consumed power will be less than what you calcuated, but you don't want any surprises. The worst situation I've seen is when a thermal/magnetic breaker was used for a DC supply output. As the DC current approached the published max asymptotically, the breaker never tripped. When the power supply ultimately failed, it took a lot of equipment out with it. Thankfully it was not my design.

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