3-Phase Energy Meter Using Microcontroller - Electronic Engineering Guide
1. Introduction
A 3-phase energy meter measures the total electrical energy consumed by a 3-phase load. This project involves designing a microcontroller-based meter that calculates energy usage by sampling voltage and current across each phase.
2. Objectives
• Measure real-time power usage on three phases.
• Accumulate energy consumption over time.
• Display the measured energy data.
• Ensure accurate readings under varying loads.
3. Components Required
• Microcontroller (e.g., ATmega328, STM32, or ESP32)
• 3 Voltage Sensor Modules (resistive divider or ZMPT101B)
• 3 Current Transformers (CTs) or ACS712 modules
• Energy Metering IC (e.g., ADE7758 – optional for accuracy)
• LCD Display (16x2 or 20x4) or UART interface
• Power Supply (5V regulated)
• EEPROM or SD card (optional for data logging)
• Protective components: resistors, capacitors, MOVs
4. Working Principle
The system uses sensors to measure the voltage and current in each phase. The microcontroller samples these signals, calculates power (P = V × I × cos(φ)), and accumulates energy (E = P × t). Results are displayed on an LCD or sent to a serial terminal.
5. Circuit Design
• Use a resistive divider network for voltage sensing or
ZMPT101B modules.
• Connect CTs or ACS712 for current measurement.
• Use precision op-amps or metering ICs for signal conditioning.
• Connect analog outputs to microcontroller ADC pins.
• Design filtering circuits to remove noise.
6. Voltage and Current Sensing
• Voltage sensors scale down mains voltage to safe levels.
• Current transformers or sensors convert load current to measurable voltages.
• Calibrate sensors to ensure accurate scaling and linearity.
• Use zero-crossing detection for power factor estimation.
7. Microcontroller Programming
• Sample ADC values of voltage and current periodically.
• Compute instantaneous power and integrate for energy.
• Implement RMS calculations and power factor logic.
• Store data in variables or log to memory.
• Use interrupts for real-time data acquisition.
8. LCD or Serial Display Interface
• Interface a 16x2 or 20x4 LCD using I2C or direct GPIO.
• Alternatively, send data over UART to a computer or Wi-Fi module.
• Display values such as voltage, current, power, energy, and power factor.
9. Calibration and Accuracy Testing
• Use reference meters or resistive loads for calibration.
• Adjust code constants or use software calibration routine.
• Test across various load types: resistive, inductive, and mixed.
• Perform long-term stability tests.
10. Applications
• Industrial 3-phase energy monitoring
• Smart metering solutions
• Energy audits in commercial buildings
• Load balancing systems
11. Limitations and Future Enhancements
• Accuracy may be limited by ADC resolution and sensor
precision.
• No wireless transmission in basic version.
• Future improvements: IoT integration, over-voltage alerts, cloud data
logging, prepaid billing system.
12. Conclusion
The 3-phase energy meter project provides a foundational understanding of power metering systems using microcontrollers. With proper calibration and component selection, it can serve as a cost-effective and scalable solution for industrial energy management.