STMicroelectronics STPMS2, EVALSTPM-3PHISO User Manual

UM2847

User manual

EVALSTPM-3PHISO: Getting started with the STPMS2 3-ph full shunt evaluation

board

Introduction

The EVALSTPM-3PHISO evaluation board implements a 3-phase AC Watt meter that meets accuracy class 0.5 according to
IEC 62053-22 standard using low-cost, electromagnetic-immune shunt sensors and advanced galvanic-isolation technology.

The evaluation board combines the high-accuracy STPMS2 metering front-end IC and the STISO621 digital isolator with
customizable firmware running on an STM32 microcontroller to compute metrology and power-quality data.

The STPMS2, a two-channel 24-bit second-order, sigma-delta modulator, measures voltage and current for each phase through
an on-board voltage divider and a shunt current sensor. It oversamples the signal using a synchronized 4 MHz clock distributed
by the microcontroller and multiplexes voltage and current sigma-delta bitstreams on a single output pin. Three STPMS2 are
used in the 3-phase system to collect voltage and current data from each phase.

The STISO621, a dual-channel digital isolator based on a 6 kV thick-oxide, galvanic-isolation technology, transfers data
between isolated domains and guarantees 6 kV VIOTM and 1.2 kV VIORM between the phases.

The FW implemented on the STPM32F413 uses digital filters for sigma-delta modulator (DFSDM) peripheral to demultiplex the
six bitstreams, convert them into 24-bit voltage and current values, and computes all metrology data in real-time every 200 µs.

The firmware also implements a Virtual COM port that provides access to internal parameters for reading metrology data,
modifying the internal configuration, and calibrating the board.

Figure 1. EVALSTPM-3PHISO image

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For further information contact your local STMicroelectronics sales office.

www.st.com

1 Safety and operating instructions

1.1 General terms

Warning:

During assembly, testing, and operation, the evaluation board poses inherent hazards due to high
voltage.

Danger:

There is danger of serious personal injury, property damage or death due to electrical shock if the
kit or components are improperly used or installed incorrectly.

The kit is not electrically isolated from the high-voltage supply AC/DC input. The evaluation board is
directly linked to the mains voltage. No barrier is present between the accessible parts and the high
voltage. All measuring equipment must be isolated from the mains before powering the board. When
using an oscilloscope with the demo, it must be isolated from the AC line. This prevents shock from
occurring as a result of touching any single point in the circuit, but does NOT prevent shock when
touching two or more points in the circuit.

All operations involving transportation, installation and use, and maintenance must be performed by skilled
technical personnel able to understand and implement national accident prevention regulations. For the purposes
of these basic safety instructions, “skilled technical personnel” are suitably qualified people who are familiar with
the installation, use and maintenance of power electronic systems.

UM2847

Safety and operating instructions

1.2 Intended use of evaluation board

The evaluation board is designed for demonstration purposes only. Technical data and information concerning the
power supply conditions are detailed in the documentation and should be strictly observed.

1.3 Installing the evaluation board

The board contains electrostatically-sensitive components that are prone to damage if used incorrectly. Do not
mechanically damage or destroy the electrical components (potential health risks).

1.4 Operating the evaluation board

To operate properly the board, follow these safety rules.

1. Work area safety:

– The work area must be clean and tidy.

– Do not work alone when boards are energized.

– Protect against inadvertent access to the area where the board is energized using suitable barriers and

signs.

– A system architecture that supplies power to the evaluation board must be equipped with additional

control and protective devices in accordance with the applicable safety requirements (i.e., compliance
with technical equipment and accident prevention rules).

– Use non-conductive and stable work surface.

– Use adequately insulated clamps and wires to attach measurement probes and instruments.

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Operating the evaluation board

2. Electrical safety:

– Proceed with the arrangement of measurement set-up, wiring or configuration paying attention to high

voltage sections.

– Remove power supply from the board and electrical loads before performing any electrical

measurement on the high voltage sections of the board.

– Once the set-up is complete, energize the board.

Danger:

Do not touch the evaluation board when it is energized or immediately after it has been
disconnected from the voltage supply as several parts and power terminals containing potentially
energized capacitors need time to discharge.

Parts of the kit are not electrically isolated from the AC/DC input. The USB interface, the JTAG
connector and the strip line connector are in the low voltage side of the board, so they can be used to
connect a host computer. Please refer to Figure 2.

3. Personal safety :

– Always wear suitable personal protective equipment such as insulating gloves and safety glasses.

– Take adequate precautions and install the board in such a way to prevent accidental touch. Use

protective shields such as an insulating box with interlocks if necessary.

Figure 2. High and low voltage sides

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2 Getting started

2.1 Hardware and software requirements

Using the EVALSTPM-3PHISO evaluation board requires the following software and hardware:

• A Windows PC (XP, Vista, Win 7, Win 8, Win 10) to eventually install the software package available on

www.st.com (optional) or to communicate through the mini-shell

• A 'USB type A to Micro-B' cable, used to power on the board (through USB connector CN1) from host PC
and to allow communication with terminal or software GUI

• JTAG arm debugging probe (optional)

• 3-Ph AC power supply and 3-Ph load

• Reference meter (optional)

The system could be run and evaluated in the following ways:

• Installing the software GUI STSW-STPM005 from www.st.com . In this case please refer to the related
documentation.

• Connecting to a shell terminal on the host PC

• Using a JTAG arm debugging probe which can be connected to JTAG connector for debugging and
programming. For this purpose, it is necessary to install the IDE “IAR embedded workbench for ARM”
version 8.5.

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Getting started

2.2 Hardware description

Figure 3. EVALSTPM-3PHISO board function description

2.2.1 Power supply

The board can be supplied alternatively by:

• connecting a USB cable to the PC

• providing 5 VDC by the coaxial jack

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Each phase STPMS2 is supplied by an independent capacitive power supply, providing the necessary 3.3 V to
the device. The jumpers P4, P7 and P8 must remain fit to use the power supply, otherwise it is bypassed.

2.2.2 Voltage and current sensing section

The STPMS2 devices onboard are configured as follows:

Table 1. STPMS2 HW configuration

PIN Connection Description

MS0 VCC HPR, amplifier GAIN selection g3 = 16

MS1 GND TC = 50 ppm/°C

MS2 GND Voltage channel ON, DATn = ~ [DAT =(CLK) ? bsV : bsC)]

MS3 GND Hard mode, BIST mode OFF

Note: For further information on STPMS2 configuration please refer to device datasheet.

The metrology section analog front-end component values are as follows:

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Running the built-in demonstration

Table 2. AFE components

Component Value Description

Shunt 0.3 mOhm Current sensor

R1 810 kOhm Voltage divider resistor (actually 3 x 270 kOhm)

R2 470 Ohm Voltage divider resistor

2.2.3 Board ratings

The ratings of the board, given by the parameters specified above, are as follows:

• Power stage supply voltage between 80 V RMS and 350 V RMS

• Maximum load current 86 A RMS

2.3 Running the built-in demonstration

The board comes with the demonstration firmware preloaded in the Flash memory. Please make sure to
download and use the latest release of STSW-STPM004 firmware from www.st.com.

Before running the application, the user should establish the connection with the 3-phase full shunt board.

Follow the steps below to run it:

• Connect the board to a PC with a 'USB type A to Micro-B' cable through USB connector CN1 to power the
board. Green LED (PWR ON) then lights up.

• First connect the board to a 3-phase generator and load as shown in the figure below, then power on the
generator:

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Figure 4. Electric connections

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Running the built-in demonstration

• When the load is connected, LED0 and LED1 blink with a frequency proportional to respectively active and
reactive power consumption.

• Connect a shell terminal to the board Virtual COM port as specified in Section 4.3 below.

• Alternatively, use the software GUI STSW-STPM005 to read/calibrate the metrology data. For more details
on the Metrology GUI please refer to its user manual.

• For application development and debug, connect the JTAG probe and open “IAR Embedded Workbench for
ARM” IDE. For STSW-STPM004 FW details please refer to related user manual.

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