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All: How can I calculate power c
- Thread starter npf
- Start date
What kind of flow controller? Are you dealing with individual 4-20 mA loop controllers, DCS, PLC, or what? Clarify your needs.
Assume that each loop requires 20 mA at 24 Vdc for the transmitter and the current to pneumatic converter. Without considering anything load for the controller itself you use about a Watt per loop. Let's play with a throw-down cabinet based upon some wild but conservative assumptions.
For a throw-down example, a full DCS cabinet with a serious multiple loop controller and I/O cards to accommodate about 96 loops may require a power supply with a dedicated 20 Amp circuit that accommodates up to 16 Amps AC load at 120 VAC. The power supply may only provide 30 or so Amps at 24 VDC. Let's say that this multi-loop controller and cabinet includes three racks of I/O boards with eight cards per chassis and eight points per card. Each loop requires two points. Based upon the power supply capacity in AC Watts, this throw-down cabinet load is just under 2000 Watts, about the same as a toaster oven. My three racks with eight cards and eight points works out to 192 points or 96 loops. Typically we only permit up to about 80% capacity but the excess may be in the next cabinet. At 96 loops that is about 20 Watts per loop. Round up if identifying circuits or HVAC loads. Perhaps 25 Watts per loop is a rational guestimate. The reality could be somewhat less.
Assume that each loop requires 20 mA at 24 Vdc for the transmitter and the current to pneumatic converter. Without considering anything load for the controller itself you use about a Watt per loop. Let's play with a throw-down cabinet based upon some wild but conservative assumptions.
For a throw-down example, a full DCS cabinet with a serious multiple loop controller and I/O cards to accommodate about 96 loops may require a power supply with a dedicated 20 Amp circuit that accommodates up to 16 Amps AC load at 120 VAC. The power supply may only provide 30 or so Amps at 24 VDC. Let's say that this multi-loop controller and cabinet includes three racks of I/O boards with eight cards per chassis and eight points per card. Each loop requires two points. Based upon the power supply capacity in AC Watts, this throw-down cabinet load is just under 2000 Watts, about the same as a toaster oven. My three racks with eight cards and eight points works out to 192 points or 96 loops. Typically we only permit up to about 80% capacity but the excess may be in the next cabinet. At 96 loops that is about 20 Watts per loop. Round up if identifying circuits or HVAC loads. Perhaps 25 Watts per loop is a rational guestimate. The reality could be somewhat less.
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