Crompton Switchboard AC Watt meters and VAr meters:
3P3W, Unbalanced Load, 2-Element
The Crompton Instruments Switchboard series of AC Watt meters and VAr meters incorporate a DC moving coil, pivot and jewel indicator with a micro-circuit watt transducer PCB to read power on three-phase systems. The most frequently selected Current and Voltage Transformers are listed on the dropdown boxes above. The selection shifts to show only compatible combinations for the range of each watt meter. In addition, these instruments may be supplied with zero-left or center-zero scale if requested.
Scaling
Watt meter and VAr meter current circuits should have equal carrying capacity because they are frequently connected in series. This means that the sum of the left and right end-scale values of the VAr meters should be equal to or greater than the full scale value of the Wattmeter (or have higher end-scale values if the instruments are center or offset-zero). Instruments measuring 10,000 kilowatts and over are marked in megawatts. Center-zero or offset-zero Watt and VAr meters are marked “IN” for left deflection and “OUT” for right deflection. Custom scales are available upon request.
Non-standard PT and CT ratios
For non-standard PT and CT ratios, use the formulas below to check that the scale value in watts for this meter falls between the minimum and maximum values as calculated below for a given combination of PT and CT ratios.
- 3-phase 3-wire Watts = Primary Amps × Primary (L-L) Volts × √3
- Example: CT ratio of 62.5:5A and a PT ratio of 3,300/120V
- 62.5A × 3,300V × √3 = 357235 watts (357kW)
- Since the nearest scale value is 350kW, calculating the minimum and maximum scale values may not be necessary, but could be instructive, depending on your situation.
- Example: CT ratio of 62.5:5A and a PT ratio of 3,300/120V
- Minimum scale value = 3p3w Watts × 0.7 and selecting next higher standard scale.
- Example: 357kW × 0.7 = 250kW
- If you know you will only be using a small portion of your maximum CT primary rating, selecting a standard scale close to your calculated minimum may be to your advantage.
- Maximum scale value = 3p3w Watts × 1.3 and select the next lowest standard.
- Example: 357kW × 1.3 = 464kW
- If you know you will be seeing frequent, momentary overloads of your maximum CT primary rating, selecting a standard scale close to your calculated maximum may be to your advantage.
- Example: If testing for a 400kW meter, the CT and PT ratio listed above (62.5:5A, 3,300/120V) would be valid.
- 250kW < 400kW < 464kW
- For this example, valid kW ranges would also include:
- 250kW (ideal for low demand)
- 300kW
- 350kW (Ideal for most circumstances)
- 400kW
- 450kW (Ideal for high demand such as momentary overloads)
- Standard, Available, and Special Ranges for 3P3W Switchboard Wattmeters
- Standard ranges appear in 4 or more of the columns below.
- Available ranges appear in the table below.
- Special ranges available upon request.
Technical Specifications
- Burden per element: Current circuit: 2VA | Voltage Circuit: 1VA
- Accuracy Class: 1.0
- Ambient range: 0° to ± 60° (32° to 104°F) std. calibration 20°C (68°F)
- Ambient influence: 0.05% per 1°C maximum
- Overloads-current: 10 x rating for 5 seconds, 1.2 x continuously
- Voltage influence: 2 x rating for 5 seconds, 1.2 x continuously voltage
- Accuracy maintained, 80 - 110% rated voltage
- Power factor influence: Accuracy maintained, 0.1 lag to 0.1 lead
- Enclosure code: 007 IP54 optional IP55 | 078 IP67
- Response time: 007 and 078 approximately 2.5 seconds
- Dielectric withstand: Live parts to case including panel 2600V RMS for 1 minute
Specifications
| Product | |
|---|---|
| Brand | Crompton |
| Series | Switchboard |
| Model | 007 |
| Form Factor | 4-Stud Mount, Switchboard: 4.5-Inch ANSI C39.1 |
| Input Range | 3P3W 120VAC L-L 0-5AAC |
| Input Frequency | 50Hz, 60Hz |
| Scale, Range, or Display | 0-25MWAC |
| Accuracy | ±1% of Full Scale |
| Tariff Code | 9028.30.1900 |
| ECCN | EAR99 |
| Current Transformers | |
|---|---|
| CT Ratio | Select or Specify or 120:5A or 125:5A or 150:5A or 200:5A or 400:5A or 500:5A or 600:5A or 750:5A or 800:5A or 1,000:5A or 1,200:5A or 1,500:5A or 1,600:5A or 2,000:5A or 2,500:5A or 3,000:5A or 3,200:5A or 3,500:5A or 4,000:5A or 5,000:5A or 6,000:5A or 7,000:5A or 7,500:5A or 8,000:5A or 9,000:5A or 10,000:5A |
| Potential Transformers | |
|---|---|
| PT/VT Turns Ratio | Select or Specify or 20/1 or 25/1 or 30/1 or 34.7/1 or 35/1 or 40/1 or 50/1 or 55/1 or 60/1 or 70/1 or 85/1 or 100/1 or 110/1 or 115/1 or 120/1 or 150/1 or 175/1 or 200/1 or 230/1 or 300/1 |