Read WT-Ser-ds.pdf text version

December 1995





The WT Series Watt Transducer is designed to monitor the power demand (kW), energy consumption (kWh), and voltage status of any three-phase, 60-cycle electrical system. 120-600 volts can be connected directly, and higher voltages can be monitored with the addition of potential transformers. Models are available for 1 amp or 5 amp current transformers. The WT Series is equipped with an exclusive diagnostic feature which identifies wiring errors with LED indication. The WT Series Watt Transducer is mounted in a NEMA 1 Enclosure (standard) and may be furnished with the Model U3889 Combination Disconnect Switch/CT Shorting Assembly mounted and wired as shown in photo. A NEMA 3R Enclosure option is also available. Optional kW and kWh Meters can be installed on the face of the unit.


· · · · · · · · · · UL/CUL Listed Built-in screw-type fuse holders Voltage selector switch (120 to 600V) Five selectable kWh pulse output rates 4-20 mA kW demand output Low voltage/phase loss alarm contact Diagnostic indicators to show wiring errors Selectable under-voltage protection level Easy-to-wire flying leads for voltage connections Integral mounting of optional kW and kWh Meters





· · · ·

Toggle switches for quick CT polarity changes LED indication of incoming voltage status LED indication of pulse output LED indication of 4-20 mA loop continuity


Input voltage 120 to 600 VAC, 60 Hz NOTE: 50 Hz available on special order Input current WT-1: 0-1 amp WT-5: 0-5 amp kW output 4-20 mA loop - externally powered (24 VDC typical), polarity insensitive. The 208/240 voltage position is calibrated for a full 4-20 mA kW output with a 240 volt input. If 208V service is being monitored, calculate the maximum kW based on 240V for the full 4-20 mA range. Max loop impedance (½): without kW meter - User supply voltage - 6 VDC 0.020 with kW meter - User supply voltage - 11.3 VDC 0.020 Solid-state relay - 50 VAC/DC max, 100 mA max NOTE: 1. If driving a DC relay coil, a reverse connection protection diode is recommended across the relay coil (such as Model 1N4004). 2. If driving an AC relay coil, a varistor across the relay coil is recommended (see Miscellaneous Controls). Phase loss contact kWh pulse rate Accuracy Humidity PT burden Operating temp Fusing CT burden Same as kWh output (closes on alarm) Five selectable rates based on voltage selection. 0.75% of full scale 0-95% noncondensing

2 VA maximum -13° to 158°F (-25° to 70°C) 0.5 amp 600V (KTK-1/2) WT-1: 0.15 VA, WT-5: 0.75 VA NOTE: If CT smaller than 200:5 is to be used, contact Kele for additional burden information. Agency approval UL listed. File # E161500 DIMENSIONS Unit without enclosure: 7"W x 10.25"H x 3.5"D (17.8 cm x 26.0 cm x 8.9 cm) Unit in small NEMA 1 enclosure: 10"W x 12"H x 4"D (25.4 cm x 30.5 cm x 10.2 cm) Unit in large NEMA 1 enclosure with U3889 Switch: 12"W x 18"H x 4"D (30.5 cm x 45.7 cm x 10.2 cm) Unit in large NEMA 3R enclosure with U3889 Switch: 16"W x 20"H x 6"D (40.64 cm x 50.8 cm x 15.24 cm)

USA 901-937-4900 · International 901-382-6084

Revised from 1/95

kWh output

KELE · · FAX 901-372-2531

INSTALLATION 1. Set the voltage selection switch to the correct line-to-line voltage. 2. CURRENT TRANSFORMER (CT) INSTALLATION: All CTs should be installed with the "H-1" side of the transformer facing the incoming power. Connect the CTs and voltage leads as shown on the Wiring Diagram (page 5, Fig. 9). Run six wires--two per CT--from the CTs to the transducer. Do not run only one return wire from the CTs. (Note for retrofit applications: If only a common return for the CTs can be used, isolate the CT inputs by installing three (3) Model 189-005 5:5 ratio wound primary CTs on the inputs.) Connections must be made as shown on the Wiring Diagram or the output values will be incorrect. The current from each CT must be in phase with its respective voltage. For example, the CT installed on "A" phase is connected to the X1 and X2 terminals on CAUTION: Opening the secondary leads of a current transformer under load can cause hazardous voltages which can injure personnel or damage the current transformer. Maintain a shorted circuit across the secondary leads whenever the current transformer is not connected to the watt transducer. A Model U3889 Switch is recommended. (See Kele catalog.)

the "A" phase CT input, and the voltage connection for L1 must be made to the "A" phase. To ensure that no wiring errors have been made, turn on the "Wiring Diagnostic" DIP switch at the bottom of the unit. If the red LEDs start blinking, refer to the following section, "Correcting Wiring Problems" (Fig. 1). If the red LEDs do not blink, turn "Wiring Diagnostic" DIP switch off and proceed to Step 3.

NOTE: Four conditions will cause the wiring diagnostics to be unreliable: 1) the amperage falls below 5% of CT rating 3) there is a leading power factor 2) the system power factor falls below 0.64 lagging 4) there is a nonsinusoidal waveform as result of harmonic distortion (caused by variable frequency drives, lighting, etc.) Fig. 1 CORRECTING WIRING PROBLEMS Red LED 1 (upper) will blink if CT polarities are not matched. Red LED 2 (lower) will blink if all three CTs are reversed or if a voltage input is not matched to its corresponding current input. If the upper red LED is blinking, change the toggle switch positions until the upper red LED goes off. Use the checklist (shown at right) of eight possible switch combinations for wiring corrections. Simply try each combination until the upper red LED light goes off. If LED 2 is still blinking after LED 1 goes off, flip all three toggle switches to the opposite position. If LED 2 is still blinking after flipping all switches, then a voltage connection is incorrectly matched to the CTs. If the voltage connection is corrected and LED 2 is still blinking, reverse all three toggle switches again. LED 1 and LED 2 should now be off. Turn "Wiring Diagnostic" DIP switch off. 3. (OPTIONAL) To verify proper CT operation, measure and record the current in the secondary of each CT. The current should be 1 amp or less on the WT-1 and 5 amps or less on the WT-5. The current is directly proportional to the respective phase load. For example, the secondary current from a 601T-102 (1000 to 5) Current Transformer will read 2.5 amps if the primary current is 500 amps (see CT ratio definition on page 4, Fig. 6). Wiring Checklist


Toggle Switch A

Toggle Switch B Toggle Switch C




4. The Undervoltage/Phase Loss circuitry is automatically activated when the "Wiring Diagnostic" switch is off. On the DIP switch, select the Undervoltage Trip Point that your application will require. (See DIP switch at bottom of unit with values of 90%, 85%, and 80%.) If a 208 volt system is to be monitored, the top DIP switch must be in the 208 Line Voltage position. Otherwise, it should be in the 120-600V position. The green "Undervoltage/Phase Loss" LED should now be on. Whenever this LED indicator is off, the output contact will close, indicating a problem with incoming voltage. 2

INSTALLATION (CONT'D) 5. (OPTIONAL) Field Installation of KW and KWH Meters · Remove power to the watt transducer. NOTE: If watt transducer has KW Meter installed, external DC voltage is required on the output terminals. · With an Allen wrench, remove the two selector switch knobs on the front panel of the watt transducer. · Remove the four screws that fasten the lower cover. Flip the CT Polarity Switches down and remove the cover. · Remove the meter position cover plate and snap in the meter from the front. NOTE: The KW Meter must be placed in the top meter position; the KWH Meter must be placed in the lower position. · Wire to the internal circuit board terminal block next to the lower selector switch (see Figs. 2 & 3 below). · Replace the cover and selector switch knobs. Return CT polarity switches to original position.


Use #22 wire or larger Remove Jumper TB1 Lower Selector Switch


White (on meter) Black (on meter) TB1

Lower Selector Switch







Transducer Circuit Board Terminal Block

NOTE: If watt transducer has kW meter installed, external DC voltage is required on the output terminals.




Transducer Circuit Board Terminal Block

OPERATION After the current and potential connections are made (see Wiring Diagram page 5, Fig. 9), the kWh pulse LED should start to blink and the kW output will be available for reading demand. NOTE: The kW output requires external power (such as 24 VDC) to supply the 4-20 mA loop current. The circuit is polarity-insensitive. If 24 VDC is not available during startup, two (2) 9V batteries connected in series with the loop will be adequate for reading the output on a meter. Fig. 4 KWH PULSE CALIBRATION CHART FOR WT-1 1 AMP CT MODEL VOLTS L-L 600 480 240/208 120 POSITION 1 WH/PULSE 0.0625 0.05 0.025 0.0125 POSITION 2 WH/PULSE 0.125 0.1 0.05 0.025 POSITION 3 WH/PULSE 0.25 0.2 0.1 0.05 POSITION 4 WH/PULSE 0.5 0.4 0.2 0.1 POSITION 5 WH/PULSE 1 0.8 0.4 0.2

Fig. 5 KWH PULSE CALIBRATION CHART FOR WT-5 5 AMP CT MODEL 600 480 240/208 120 0.3125 0.25 0.125 0.0625 0.625 0.5 0.25 0.125 3 1.25 1 0.5 0.25 2.5 2 1 0.5 5 4 2 1

DEFINITIONS AND FORMULAS Fig. 6 DEFINITIONS E I mA out Wh/Pulse = = = = Line-to-line voltage CT primary amps (For example: 500 to 5 would be 500) Output current in milliamps from the WT Series Transducer which represents instantaneous kW demand. Watt/hours per pulse output from the WT Series Transducer based on the switch position and voltage. The value is read from the kWh Calibration Charts. CT primary current divided by the CT secondary current. (For example: 500 to 5 CT = 100) PT primary voltage divided by PT secondary voltage. (For example: 4800 to 120 = 40) Accumulated pulses from kW pulse output over a monitored time period (e.g., 1 month)

CT ratio = PT ratio = Pulse count =


A. kW maximum =

E x I x 1.73 1000 E x I x 1.73 x (mA out - 4) 1000 x 16

B. kW demand = (instantaneous)

C. kWh/Pulse = Wh/Pulse x CT ratio x PT ratio (if used) 1000 CT pulse D. kWh = Wh/Pulse x ratio x count x (consumption) 1000 E. sec/pulse = (maximum pulse rate) PT ratio (if used)

Example of How to Use Formulas: A Model WT-5 Transducer is used with three Model 601T501 (500 to 5) Current Transformers and a 3PT3-60-482 (4800V primary to 120V secondary) three-phase Potential Transformer (in this section of Kele catalog). The voltage selector should be set to 120V. Position 3 pulse rate is chosen in this example. The measured kW demand output is 8.5 mA and the pulse count for the month is 84000. Below are examples of calculations using this information:

kW maximum = 4800 x 500 x 1.73 = 4152 kW 1000 kW demand = 4800 x 500 x 1.73 x (8.5 - 4) = 1168 kW (instantaneous) 16000 kWh/Pulse = 0.25 x 100 x 40 = 1 1000 kWh = 0.25 x 100 x 84000 x 40 = 84000 kWh (consumption) 1000

3600 x kWh/pulse (from formula C) kW maximum (from formula A)

Fig. 8 (Optional) QUICK CHECK OF THE OUTPUTS 1. Calculate the average of the three line currents (IAVG) with a portable clamp-on ammeter. 2. Calculate the approximate kW as follows: Approx. kW = E (line-to-line) x I (avg. current) x 1.73 x power factor (use 0.9 if unknown) (instantaneous) 1000 Compare the calculated value for approximate kW to your calculated value for kW demand (see formula B above). The values should be the same.* 3. Calculate the approximate sec/pulse as follows: 3600 x kWh/pulse (from formula C) approx. kW Compare the approx. sec/pulse to the time the pulse output (or green output LED) goes through one complete cycle (ON+OFF time).* *Since your power factor figure may be approximate, allow for some variation in the calculations. Also, calculations may vary if there is a time delay between readings in which a load change has occurred.




CAUTION: Lethal voltages may be present across the secondary terminals of all current transformers. Keep these terminals shorted or connected to the transducer.


WT INSTALLATION CHECKLIST 1. 2. 3. 4. 5. 6. 7. 8. 9. If Model U3889 Switch (see Kele catalog) is used, close the CT shorting switches and open the voltage switches. Install CTs per instructions. NOTE: The circuit should not be open on the secondary leads. Make voltage connections. Remember to match with same phase CT input. Wire kWh pulse output and undervoltage/phase loss circuits if used. Wire kW (4-20 mA) output if used. Remember to use external DC voltage. Set voltage selector to proper line-to-line voltage. If 208V, set the Line Voltage 208 DIP switch. NOTE: This switch only affects the undervoltage protection, not the kW/kWh output. If Model U3889 Switch is used, open the CT shorting switches and close the voltage switches. Set "Wiring Diagnostic" DIP switch to the "on" position to check for wiring problems. If the red LED lights are not blinking, wiring is correct. Proceed to Step 10. If red LED lights are blinking, follow the instructions below: If upper red LED is blinking, change toggle switches to correct wiring (see checklist on page 2). Ignore lower red LED light until upper LED light is off. If lower red LED is blinking after upper LED is off, reverse all three toggle switches. If lower red LED is still blinking, put all three toggle switches in original position and check for incorrect voltage connection. If voltage wiring error is found and corrected, but lower red LED is still blinking, reverse all three toggle switches again. 10. Switch off "Wiring Diagnostic" DIP switch after correcting wiring problems. 11. Set undervoltage protection level on DIP switch. 12. If "Undervoltage/Phase Loss" green LED is off, check for incoming voltage problem. 13. Green LED for kWh pulse output should be blinking. 14. Change the pulse output rate selector switch to the desired rate (see Figs. 4 & 5 on page 3). 15. Check the green kW demand LED. If it is off, there is an open circuit in the loop. 16. To find the formulas for kW/kWh, go to Fig. 7, page 4. If you have any questions, please call a KELE Sales Engineer at 901-382-4300. ORDERING INFORMATION


Basic Model in NEMA 1 Enclosure 1 5 1 amp input from current transformer 5 amp input from current transformer Options (Leave blank for standard unit in NEMA 1 Enclosure) SW in NEMA 1 Screw Cover Enclosure (hinged for meter options) with Model U3889 Switch and Cover, mounted and wired

SW3R in NEMA 3R Hinged Cover Enclosure with Model U3889 Switch and Cover, mounted and wired K1 K2 K3 KWH Meter mounted on unit KW and KWH Meters mounted on unit (Specify voltage and CT ratio). KW Meter mounted on unit (Specify voltage and CT ratio).





Example: WT-1-SW-K1 WT Series Watt Transducer for 1 amp secondary CT in NEMA 1 Enclosure with U3889 Switch, Cover and kWh Consumption Meter installed on unit.

USA 901-937-4900 · International 901-382-6084

KELE · · FAX 901-372-2531


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