IDT90E36三相電能表設(shè)計(jì)方案
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時(shí)間：2012-04-23
來(lái)源：網(wǎng)絡(luò)
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The 90E36 is a poly-phase high performance wide-dynamic range metering IC. The 90E36 incorporates 7 independent 2nd order sigma-delta ADCs, which could be employed in three voltage channels (phase A, B and C) and four current channels (phase A, B, C and neutral line) in a typical three-phase four-wire system.
The 90E36 has an embedded DSP which executes calculation of active energy, reactive energy, apparent energy, fundamental and harmonic active energy over ADC signal and on-chip reference voltage.
The DSP also calculates measurement parameters such as voltage and current RMS value as well as mean active/reactive/apparent power.
A four-wire SPI interface is provided between the 90E36 and the external microcontroller. In addition, DMA mode can be used for 7-channel ADC raw data access, offering more flexibility in system application.
The 90E36 is suitable for poly-phase multi-function meters which could measure active/reactive/apparent energy and fundamental/harmonic energy either through four independent energy pulse outputs CF1/CF2/CF3/CF4 or through the corresponding registers.
With the on-chip THD and DFT engine, all phases’ THD and DFT results can be directly accessed through related registers, thus simplifying hardware design in Data Acquisition Terminals.
IDT’s proprietary ADC and auto-temperature compensation technology for reference voltage ensure the 90E36’s long-term stability over variations in grid and ambient environment conditions.
90E36主要特性:
Metering Features
? Metering features fully in compliance with the requirements of IEC62052-11, IEC62053-22 and IEC62053-23, ANSI C12.1 and ANSI C12.20; applicable in class 0.5S or class 1 poly-phase watt-hour meter or class 2 poly-phase var-hour meter.
? Accuracy of ±0.1% for active energy and ±0.2% for reactive energy over the dynamic range of 6000:1.
? Temperature coefficient is 6 ppm/ ℃ (typical) for on-chip reference voltage.
? Single-point calibration on each phase over the whole dynamic ange for active energy; no calibration needed for reactive/ apparent energy.
? ±1 ℃ (typical) temperature sensor accuracy.
? Electrical parameters measurement: less than ±0.5% fiducial error for Vrms, Irms, mean active/ reactive/ apparent power, frequency, power factor and phase angle.
? Active (forward/reverse), reactive (forward/reverse), apparent energy with independent energy registers. Active/ reactive/ apparent energy can be output by pulse or read through energy registers to adapt to different applications.
? Programmable startup and no-load power threshold, special designed of startup and no-load circuits to eliminate crosstalk among phases achieving better accuracy especially at low power conditions.
? Dedicated ADC and different gains for phase A/B/C and Neutral line current sampling circuits. Current sampled over current transformer (CT) or Rogowski coil (di/dt coil); phase A/B/C voltage sampled over resistor divider network or potential transformer (PT).
? Programmable power modes: Normal mode (N mode), Idle mode (I mode), Detection mode (D mode) and Partial Measurement mode (M mode).
? Fundamental (CF3, 0.2%) and harmonic (CF4, 1%) active energy with dedicated energy and power registers.
? Total Harmonic Distortion (THD) and Discrete Fourier Transform (DFT) functions for 2 ~ 32 order harmonic component. THD and DFT results available in SPI accessible registers. Both voltage and current of all phases processed within the same time period.
? Event detection: sag, phase loss, reverse voltage/ current phase sequence, reverse flow, calculated neutral line current INC overcurrent sampled neutral line current INS overcurrent and THD+N over-threshold.
Other Features
? 3.3V single power supply. Operating voltage range: 2.8V~3.6V. Metering accuracy guaranteed within 3.0V~3.6V.
? Four-wire SPI interface with Direct Memory Access (DMA) mode to stream out 7-channel ADC raw data.
? Parameter diagnosis function and programmable interrupt output of the IRQ interrupt signals and the WarnOut signal.
? Programmable voltage sag detection and zero-crossing output.
? CF1/CF2/CF3/CF4 output active/ reactive/ apparent energy pulses and fundamental/ harmonic energy pulses respectively.
? Crystal oscillator frequency: 16.384 MHz. On-chip two capacitors and no need of external capacitors.
? TQFP48 package.
? Operating temperature: -40 ℃ ~ +85 ℃ .
90E36應(yīng)用:
? Poly-phase energy meters of class 0.5S and class 1 which are used in three-phase four-wire (3P4W, Y0) or three-phase threewire (3P3W, Y or Δ) systems.
? Data Acquisition Terminal.
? Power monitoring instruments which need to measure voltage, current, THD, DFT, mean power, etc.
圖1.90E36方框圖
本文檔介紹了采用IDT90E32/36 三相電能計(jì)量芯片設(shè)計(jì)三相電能表的應(yīng)用。
90E32/36 可用于0.5S 級(jí)或1 級(jí)三相有功電能表和無(wú)功電能表的設(shè)計(jì)，并可支持三相四線(3P4W) 或三相三線(3P3W)的接線方式，90E36 還可用于諧波表的設(shè)計(jì)。
芯片采用3.3V 單一電源供電。在典型的3P4W 設(shè)計(jì)中，需要三個(gè)獨(dú)立的變壓器進(jìn)行供電。交流電源經(jīng)整流和穩(wěn)壓后輸出3.3V 到芯片數(shù)字電源DVDD，芯片模擬電源AVDD 應(yīng)直接與DVDD 連接。
芯片內(nèi)部具有上電復(fù)位電路，外部RESET 引腳可以接一個(gè)10kΩ 電阻到DVDD 和一個(gè)0.1μF 電容到GND。芯片具有高穩(wěn)定性的片上基準(zhǔn)電源，Vref 引腳需要外接10μF 和0.1μF 兩個(gè)電容。
芯片采用16.384MHz 頻率做為系統(tǒng)工作頻率，芯片內(nèi)建了晶體振蕩電路和10pF 的匹配電容，應(yīng)用時(shí)只需要在OSCI 和 OSCO 引腳接一個(gè)16.384MHz 晶體。
90E32 芯片提供三路電壓(V1、V2、V3) 和三路電流(I1、I2、I3)的A/D采樣，90E36還額外多提供一路電流采樣(I4)。
電流采樣中的I1 和I3 可以通過(guò)設(shè)置進(jìn)行互換，以適應(yīng)不同的PCB 設(shè)計(jì)。
芯片提供了一個(gè)四線的SPI 接口(CS，SCLK，SDI，SDO)與外部MCU 連接，MCU 可通過(guò)SPI 接口對(duì)芯片進(jìn)行配置和讀寫寄存器。90E36 還可支持Master 模式的SPI，即DMA 模式。
在DMA 模式下，芯片會(huì)以高達(dá)1800kbps 的速率將A/D 的原始采樣數(shù)據(jù)通過(guò)Master SPI 輸出給外部微處理器進(jìn)行處理。芯片提供了四個(gè)電能脈沖輸出引腳：有功電能脈沖CF1、無(wú)功電能脈沖CF2( 也可配置成全波視在電能脈沖輸出)、基波有功電能脈沖CF3、諧波有功電能脈沖CF4，可用于芯片電能計(jì)量的校準(zhǔn)，同時(shí)也可以將脈沖信號(hào)連接到MCU 進(jìn)行電能累計(jì)。
芯片提供了三個(gè)過(guò)零信號(hào)輸出引腳ZX0、ZX1、ZX2，可設(shè)置不同的電壓或電流信號(hào)做為過(guò)零判斷。
芯片提供了IRQ0、IRQ1、WarnOut 輸出引腳，分別輸出不同等級(jí)的中斷和報(bào)警信號(hào)。
三相四線(3P4W) 應(yīng)用:
圖2.90E36三相四線電流互感器(CT)電表電路圖
三相四線電流互感器(CT)電表材料清單:
圖3.90E36三相四線Rogowski線圈電表電路圖
三相四線Rogowski線圈電表材料清單:
圖4.90E36三相三線電表電路圖
三相三線電表材料清單(BOM):
基爾霍夫電流相關(guān)文章:基爾霍夫電流定律
電能表相關(guān)文章:電能表原理
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