Working principle of three-phase prepaid energy meter

The working principle of a three-phase prepaid energy meter is based on electronic metering technology. Through voltage and current sampling circuits, the three-phase electrical signals are converted into digital signals, and then the microprocessor performs energy calculation, data processing, and communication transmission to achieve high-precision metering and intelligent management.

1、 Core components

Voltage/current sampling circuit

Voltage sampling: Reduce the three-phase voltage signal proportionally to a manageable range through resistance voltage division or voltage transformer (PT).

Current sampling: Using current transformers (CT) or manganese copper splitters to convert high currents into low current signals.

Signal conditioning: After filtering, amplifying, and analog-to-digital conversion (ADC), the sampled signal is output as a digital signal for subsequent processing.

Measurement chip

Specialized energy metering chips (such as ADE7755, ATT7022, etc.) perform high-speed sampling of digital signals and calculate parameters such as active power, reactive power, and power factor through Fourier transform (FFT) or digital multipliers.

Support functions such as time-sharing measurement, demand statistics, and four quadrant reactive power measurement.

Microprocessor (MCU)

Responsible for coordinating the work of various modules, executing energy data calculation, storage, display, and communication protocol processing.

Built in real-time clock (RTC), supporting time sensitive functions such as rate switching and demand cycle freezing.

Storage unit

Using non-volatile memory (such as EEPROM or Flash) to store cumulative power consumption, demand data, event records (such as power failure, calibration), and meter parameters.

communication interface

Support RS-485, PLC (power line carrier), GPRS/4G, LoRa and other communication methods to achieve remote meter reading, parameter setting and firmware upgrade.

Display and buttons

A liquid crystal display (LCD) screen displays current information such as battery level, voltage, current, and power; The button module is used for local queries or parameter modifications.

Power management

Convert the grid voltage to 5V/3.3V low voltage through transformers or switching power supplies to supply power to internal circuits; Built in backup battery ensures data is not lost during power outages.

2、 Working principle and process

Signal acquisition and conversion

The three-phase voltage and current signals are converted into digital signals by the sampling circuit and sent to the metering chip.

Energy Measurement