With the wide application of high-precision measuring chips in measuring instruments, intelligent electrical measuring instruments have made great progress in both volume and function. It is getting smaller and smaller in size, more and more functions, and more diverse in communication modes. From general Modbus-RTU to MBUS, CAN BUS, BACNET and PROFITNET, the application of these communication protocols can enable the measurement data at the bottom to be transmitted to the management equipment or management software at the upper level in a faster and more stable way. Let's take ELECNOVA LNF96EY multi-function electrical measuring meter and LNF96I3Y three-phase ammeter as examples to introduce the functions and wiring methods of these two meters.
High-precision measurement of all commonly used electrical parameters in three-phase power grid system: three-phase current, three-phase voltage, active power, reactive power, power factor, grid frequency, active energy, reactive energy, and communication interface and electric energy pulse output function. Adopt Modbus-RTU communication protocol to realize LCD display and remote digital communication. It has the characteristics of convenient installation, simple wiring, small quantities of work, field programmable setting of input parameters, and can complete the networking communication with different PLCs and industrial control computers in the industry.
Dural active energy
Quadrant reactive energy
Display: LCD display
Communication: MODBUS-RTU protocol
Output: 2 D/I, 2 R/O, 1 Energy Pulse
Power quality: 2~15th Harmonic
The intelligent three-phase ammeter adopts industrial components. All the boundaries with the outside world are electrically isolated, with built-in protection circuit and power filter. There are usually three connection methods for three-phase ammeters, namely, direct access, access by current transformer and access by voltage transformer.
1. Direct access method: If the load function is within the allowable range of the watt-hour meter, the direct access method can be used. At present, the three-phase ammeter of the direct access method is mainly installed with din rail. Din rail mounted ammeter can be divided into two types: upper in and lower out, and lower in and lower out.
2. Current transformer calculation method: when measuring the power consumption of single-phase circuit with large current by three-phase ammeter, because the current flowing through the line is large, such as 300-600A or above, in this case, if the direct access method is adopted, it will be more likely to endanger personal safety, so current transformer is usually used to change the current, and the large current is replaced by a small current, that is, the current that the ammeter can bear, and then the measurement. Taking ELECNOVA three-phase ammeter LNF96I3Y as an example, the secondary side current of this meter is 1A or 5A, that is, the customer only needs to select a current transformer with a transformation ratio of 1A or 5A according to their maximum current value to configure this meter.
3. Through voltage transformer calculation method: in addition to the current transformer connection method mentioned above, in some specific high voltage main circuits, they cannot be directly connected. Instead, voltage and current transformers should be used for voltage and current conversion. The large voltage and current should be converted into small voltage and small current, that is, the voltage and current that the ammeter can bear. Take the ELECNOVA three-phase ammeter LNF96I3Y as an example. In addition to the standard 1A and 5A current, this ammeter has 333mV alternative. The customer only needs to select the voltage transformer or flexible coil with the voltage secondary side transformation ratio of 333mV, which can easily connect the meter.
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