Application Note: AN-115
Continental Control Systems LLC
June 2008 LCDA-EP Energy & Power Display
Overview
The energy and power display has eight digits with an adjustable scale factor and decimal point position, to allow for the accurate display of energy levels from hundredths of a watthour to 100,000 megawatt-hours and power levels from tenths of a watt to megawatts. By adjusting the scale factor and decimal point position, you can display energy in watt-hours, kilowatt-hours, or megawatt-hours and power in watts, kilowatts, or megawatts. The energy and power display is self-powered for use with the Advanced Pulse WattNode models with an output frequency up to 20Hz. For Advanced Pulse WattNode models with an output frequency greater than 20Hz an external DC power supply and pull-up resistor are required. The long life battery maintains the total energy value, even if power to the WattNode fails. To switch the display between Power and Energy, press the T/R button. When the display has an R in the leftmost position, it will display power (ratemeter mode). Otherwise, it will display energy (totalizer mode). The RST button resets the energy total to zero. If you wish to disable this feature, use program screen 6 as described in the Durant manual. Wiring
Low Pulse Frequency (up to 20Hz)
Connect the WattNode's `P1' terminal of the output to the IN B (Terminal 2) on the LCD display. Connect the WattNode's `COM' terminal of the output to the GND (Terminal 1) on the LCD display.
RST 4
Output
P3 P2 P1 COM
OA / OB / OC / 7 +10-30VDC 6 DC Common 5 Enable/R IN A 3 IN B 2 GND 1 WATTNODE ®
WNB - 3Y-208- P
N
Status Status Status
OA / OB / OC / CT CT CT Figure 1: LCDA-EP Low Pulse Frequency Wiring Diagram High Pulse Frequency (greater than 20Hz)
Connect the WattNode's `P1' terminal of the output to the IN A (Terminal 3) on the LCD display. Connect the WattNode's `COM' terminal of the output to the GND (Terminal 1) on the LCD display. Add a pullup resistor on the P1 line as shown below. LCDA-EP Energy & Power Display 1 Continental Control Systems, LLC
+5V to +28Vdc Resistor values See Table 1
P3 P2 P1 COM
OA / OB / OC / AN-115 RST 4 7 +10-30VDC 6 DC Common 5 Enable/R IN A 3 IN B 2 GND 1 Output WATTNODE ®
WNB - 3Y-208- P
N
Status Status Status
OA / OB / OC / CT CT CT Figure 2: LCDA-EP High Pulse Frequency Wiring Diagram Full-Scale Pulse Frequency 20 Hz 50 Hz 100 Hz 200 Hz 600 Hz Pull-up to 5.0V Recd (Min-Max) Pull-up to 12V Recd (Min-Max) Pull-up to 24V Recd (Min-Max) 20k (1.0k-300k) 10k (1.0k-130k) 4.7k (1.0k-62k) 2.0k (1.0k-33k) 2.0k (1.0k-12k) 47k (2.4k-470k) 20k (2.4k-200k) 10k (2.4k-100k) 4.7k (2.4k-47k) 4.7k (2.4k-16k) 100k (4.7k-540k) 47k (4.7k-270k) 20k (4.7k-130k) 10k (4.7k-68k) 10k (4.7k-22k) Table 1: Recommended Pull-up Resistors Programing the Display
The LCDA-E is shipped pre-programmed if ordered with an Advanced Pulse WattNode and current transformers. To make changes to the original program, follow the steps below: Program Energy Display (Watt-hours, Kilowatt-hours, Megawatt-hours)
Refer to the Durant Totalizer/Ratemeter Installation manual for details on programming the scale factors and installing the LCD display. 1) Select a display format for energy from the following table. Your choice will affect both display resolution, and time until display overflow, so you may wish to try more than one format to find the optimum choice. When in totalizer mode, the LCD display will show the count of received pulses times the totalizer count scale value (CntScale). The decimal point is then superimposed on the displayed number--to understand this better, note that CntScale is the same when displaying kilowatt-hours or thousandths of megawatt-hours; the only difference is the position of the decimal point.
Display Format 0000000.0 Watt-hours 00000000 Watt-hours 00000.000 Kilowatt-hours 000000.00 Kilowatt-hours 0000000.0 Kilowatt-hours 00000000 Kilowatt-hours 00000.000 Megawatt-hours Multiplier Recommended CT Sizes 10 1 1 0.1 0.01 0.001 0.001 5­30 amps 5­100 amps 5­100 amps 15­600 amps 100­1500 amps 600­1500 amps 600­1500 amps Note: Watt-hours, kilowatt-hours, or megawatt-hours will not appear on the LCD display. LCDA-EP Energy & Power Display 2 Continental Control Systems, LLC AN-115 2) Compute the totalizer count scale value. CntScale = WHpPpA · CTAmps · Multiplier
Where WHpPpA is the `Watt-hours per pulse per CT Rated Amp' from the back label of the WattNode (also found in Table 8 of the Advanced Pulse WattNode Manual). CTAmps is the rated current of the current transformers being used, and Multiplier comes from the table above. 3) If the CntScale is greater than 99.9999, then you will have to pick a smaller multiplier. Generally, CntScale values greater than 10.0000 will cause the display to overflow too quickly. If CntScale is less than 0.0500, then there is the possibility that the rounding error may become too large. To check the rounding error, follow step 4. 4) To compute the rounding error, round CntScale to four decimal places (xx.xxxx) to get RndCntScale. Compute the error with the following equation: Error% = 100 · RndCntScale ­ CntScale CntScale Generally, it is desirable to keep the error below 0.25% so that it does not significantly affect the total system accuracy. If the error is too large, then change to a display format with a larger Multiplier. 5) Check the time to display overflow at continuous maximum power consumption. DaysToOverflow = 1150 CntScale · FSHz FSHz is the `Full-scale pulse frequency' from the back label of the WattNode (also found in Table 7 of the Advanced Pulse WattNode Manual). Under normal conditions, the average load will be less than maximum power, so the actual time to display overflow will typically be longer than DaysToOverflow. When the display overflows, it wraps around to zero and starts counting up again. If the DaysToOverflow is too small, then change to a display format with a smaller Multiplier. Making Multiplier 10 times smaller will make DaysToOverflow 10 times larger. 6) Once you have found the desired display format and CntScale value, program them into the LCD as described in the Durant manual. Enter CntScale in programming screen 1. Position the decimal point in programming screen 2 to match the Display Format selected in the table above. Programming screens 3­6 are not used at this time. Program Power Display (Watts, kilowatts, megawatts)
1) For the power display, the LCD will display the input pulse frequency times the scale factor. The decimal point is then superimposed on the resulting number. Start by selecting the WattNode model from the table below.
Model Number of CTs Vc WNB-3Y-208-P WNB-3Y-400-P WNB-3Y-480-P WNB-3Y-600-P WNB-3D-240-P WNB-3D-400-P WNB-3D-480-P
LCDA-EP Energy & Power Display 1, 2, or 3 1, 2, or 3 1, 2, or 3 1, 2, or 3 1, 2, or 3 1, 2, or 3 1, 2, or 3 120 230 277 347 120 230 277
3 Continental Control Systems, LLC AN-115 2) Compute maximum measured power: Pm(watts) = Vc · CTAmps · NumOfCTs
where Vc comes from the above table, CTAmps is the rated current of the current transformers being used, and NumOfCTs is the number of CTs being used with the WattNode. The WattNode can measure power levels up to 50% over the rated limits, so you may want to increase Pm by up to 50% if you wish to allow some overhead. If the WattNode outputs a power greater than the display can handle, then the display will show `----`. 3) Choose a row so that Pm is less than Expected Maximum Power with the Desired Display Format.
Expected Maximum Power Desired Display Format1 Display Resolution Scale FactorEquation (20Hz Output)2 Rate Multiplier 999.9 W 9999 W 9.999 kW 99990 W 99.99 kW 999.9 kW 9999 kW 9.999 MW
1 2 000.0 W 0000 W 0.000 kW 00000 W 00.00 kW 000.0 kW 0000 kW 0.000 MW 0.1 W 1W 1 W (0.001 kW) 10 W 10 W (0.01 kW) 100 W (0.1 kW) 1 kW 1 kW (0.001 MW) Vc · CTAmps · 3 / 2 Vc · CTAmps · 3 / 20 Vc · CTAmps · 3 / 20 Vc · CTAmps · 3 / 200 Vc · CTAmps · 3 / 200 Vc · CTAmps · 3 / 2000 Vc · CTAmps · 3 / 20000 Vc · CTAmps · 3 / 20000 1 1 1 10 1 1 1 1 W, kW, or MW will not appear on the LCD display. The scale factors are valid only when used with a WattNode with a 20Hz maximum frequency output. 4) Compute the scale factor. On program mode screen 3 enter your computed scale factor. Example: if your computed scale factor is 12.4137, round to 12.41, enter the four digits 1241, and then move the decimal point so that 12.41 is displayed. 5) On program mode screen 4 adjust the decimal point location to match the Desired Display Format. 6) On program mode screen 5 set the Rate Multiplier to 1 or 10 as shown in the table above. © 2008 Continental Control Systems http://www.ccontrolsys.com WattNode is a registered trademark of Continental Control Systems, LLC This document is subject to change without notice.
LCDA-EP Energy & Power Display 3131 Indian Rd., Suite A Boulder, CO 80301 Phone: (303) 444-7422 FAX: (303) 444-2903
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