ROOTECH ACCURA 3550 Communication User Guide

ACCURA 3550

Digital Power Meter for Rectifier Panel

Replaces TD and RTU

Communication User Guide[English]

Rev 1.2

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Notice

Limitation of Liability

Rootech Inc. reserves the right to make changes in the device specifications shown in this User’s

Guide without notice. Rootech Inc. advises customers to obtain the latest specifications of device

before giving orders to confirm that the information being relied on by the customer is up to date.

In the absence of written agreement to the contrary, Rootech Inc. assumes no liability for Rootech

Inc. applications assistance, customer’s system design, or infringement of patents or copyrights of

third parties by or arsing from the use of devices described herein.

Except to the extent prohibited by applicable law, under no circumstances shall Rootech Inc. be

liable for consequential damages sustained in connection with said product and Rootech Inc.

neither assumes nor authorizes any representative or other person any obligation or liability other

than such as is expressly set forth herein.

The information contained in this document is believed to be accurate at the time of publication,

however, Rootech Inc. assumes no responsibility for any errors which may appear here and

reserves the right to make changes without notice.

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Standard Compliance

CE Approved

EN61326 and IEC61010

MEASURING EQUIPMENT

35DX

E258934

KSA 9001:2001/ ISO 9001:2001

QMS-1347

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Warranty Information

For products and software that are sold or licensed by Rootech Inc. during the period from the

date of receipt by you until the present, Rootech warrants only to the original purchaser

The purchased products other than software shall be substantially free from material defects in

material and workmanship by Rootech for two years from the date receipt by you.

The software itself is provided “as is” without any warranty of any kind.

Limitation of Warranty

These limited Warranties shall not apply to any product that has been subject to alteration,

accident, misuse, abuse, neglect or failure to exactly follow Power Measurement's instructions for

operation and maintenance.

In order for the original purchaser to make a claim under the warranties described above, the

original purchaser must promptly contact Rootech headquarter. After receiving such notice,

Rootech may either in Rootech’s sole discretion, examine the product at the original purchaser’s

site or issue shipping instructions to the original purchaser to return the relevant product to

Rootech for examination at the original purchaser’s expense, transportation charges prepaid.

If after examining the product Rootech reasonably confirms that such examined product does not

meet the warranties, then the original purchaser’s sole remedy and Rootech’s sole obligation or

liability shall be, at Rootech’s option, to repair, replace or refund the price paid for that product.

Regardless of whether any remedy set forth herein fails of its essential purpose, except to the

extent the following limitation is prohibited by applicable law, Rootech shall not, in any event or

under any legal claim or theory, be liable to the original purchaser or any other person or entity

for special, indirect, incidental, punitive, liquidated, special or consequential damages whatsoever

with respect to any purchased product, including, without limitation, business interruption, loss of

use, profit or revenue, even if Rootech has been advised of the possibility of such damages. To the

extent that a limitation or exclusion of consequential damages are prohibited by applicable law,

then Rootech’s liability shall be limited to twice the amount of the relevant purchased product.

Rootech shall not be liable for any claim- other than a claim solely for the breach of one of the

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above warranties that is made in accordance with the above described procedures- made by the

original purchaser, its employees, agents, or contractors for any loss, damage, or expense

incurred due to, caused by, or related to any purchased product

Any technical assistance provided by Rootech's personnel or representatives in system design shall

be deemed to be a proposal and not a recommendation. The responsibility for determining the

feasibility of such proposals rests with the original purchaser and should be tested by the original

purchaser.

It is the original purchaser’s responsibility to determine the suitability of any product and

associated documentation for its purposes. The original purchaser acknowledges that 100% "up"

time is not realizable because of possible hardware or software defects. The original purchaser

recognizes that such defects and failures may cause inaccuracies or malfunctions.

Only the terms expressed in these limited Warranties shall apply and no distributor, corporation or

other entity, individual or employee of Rootech or any other entity is authorized to amend, modify

or extend the Warranties in any way.

Headquarter

102-611, Digital Empire2, 486, Sin-dong, Yeongtong-gu,

Suwon, Korea

Tel : +82-31-695-7350 Fax : +82-31-695-7399

Homepage

www.rootech.com

E-mail

[email protected]

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Revision History

The following versions of the Accura 3550 User’s Guide have been released.

Revision #

Revision date

Description

Firmware version

Revision 1.0 2006. 06. 30 Initial draft

Revision 1.1 2007. 04. 24 Adding Short-formed data block 1.16

Revision 1.2 2007. 07. 13 Figure and comm examples modified

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Contents

Chapter 1 Serial Communication .............................................................................................. 11

Overview ............................................................................................................................... 11

Communication ..................................................................................................................... 12

Packet Recognition Time ................................................................................................. 13

Holding Time before transmitting Request Packet .......................................................... 13

Chapter 2 Communication Setup ............................................................................................ 14

Communication Wiring ......................................................................................................... 14

Setup ..................................................................................................................................... 15

Setup Mode .................................................................................................................... 15

Chapter 3 Modbus RTU Protocol ............................................................................................. 17

Packet Field of Modbus RTU ........................................................................................... 17

Exception Responses ...................................................................................................... 18

Broadcast Packets ........................................................................................................... 19

Packet Communications ........................................................................................................ 20

Function 03: Read Holding Registers .............................................................................. 20

Function 06: Write Single Register to Meter .................................................................... 21

Function 16: Write Multiple Registers to Meter ............................................................... 21

Reserved Registers ......................................................................................................... 22

Invalid Registers ............................................................................................................. 22

Chapter 4 Modbus RTU Map ................................................................................................... 23

Address Map Sections ........................................................................................................... 23

Overview ....................................................................................................................... 23

System information section ............................................................................................ 24

Configuration section ..................................................................................................... 24

Measurement section ..................................................................................................... 26

THD, k Factor section ..................................................................................................... 27

Demand, Maximum, Minimum section ........................................................................... 27

Harmonic section ........................................................................................................... 29

Vector diagram section† ................................................................................................. 30

Waveform section .......................................................................................................... 31

Demand trend section .................................................................................................... 32

Reset section .................................................................................................................. 32

DC module section† ........................................................................................................ 33

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Short-formed data block Section .................................................................................... 34

Data Formats ........................................................................................................................ 37

Parameter Calculation ........................................................................................................... 39

Fixed sale ....................................................................................................................... 39

Variable scale ................................................................................................................ 39

APPENDIX A CRC-16 Calculation ............................................................................................ 41

CRC-16 Generation ............................................................................................................... 41

CRC Generation Procedure ............................................................................................ 41

CRC table ....................................................................................................................... 42

APPENDIX B Modbus RTU C Code Example ............................................................................. 43

Data Receiving and CRC Generation& Checking ................................................................... 43

Request Packet Generation ............................................................................................ 43

Response Packet Checking ............................................................................................. 43

Response Packet Checking ............................................................................................. 44

CRC functions................................................................................................................. 44

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Chapter 1 Serial Communication

Overview

Accura 3550 has a RS485 port on the rear side of meter for Master/Slave communication in the

field, and supports Modbus RTU protocol.

Modbus RTU protocol is a industry standard to efficiently transfer information of measuring and

control between master[PC or PLC] and slave[local devices, Accura 3300/3500/3550/7500].

Master/Slave Multi-drop

 All communications on network conforms to a Master/Slave scheme.

 Master will initiate and control all information on the communications loop.

 Under no circumstances A Slave device initiate a communications sequence.

 All communications occurs in the form of Packet, a packet being simply a serial string of 8-

bit bytes.

 All Packets transmitted by the Master are requests. All Packets transmitted by a Slave are

responses.

 At most one Slave can respond to a single request from a Master.

Modbus RTU Protocol

 Industry standard protocol for general users.

 Modbus RTU is recommended.

 Designed according to Modicon Modbus RTU specifications.

 Provides selective data communications by address map.

 Most of automation programs provides the driver for Modbus RTU.

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Communication

The default serial communication setup of Accura 3550 is 8 data bits, even parity, 1 stop bit

The RS485 communications allows multiple devices to be connected on the same bus. Up to 32

devices can be connected on a single RS485 bus, which consists of a shielded twisted pair cable

more than AWG 22[0.33mm2]. The overall length of the RS485 cable connecting all devices

cannot exceed 1.2km[ or 4000ft].

Fig 1.1 RS485 Multi-drop Connection Diagram

Warning

The above T bridge – branched off in the middle of communication line- can not guarantee the

communication reliability by voltage-drop on the line.

To connect an RS485 communication bus to a computer or other RS232 equipped device, a

RS232 to RS485 converter is required. The communication between computer and Accura 3550 is

to connect the Pins, Ta, Tb of the Accura 3550 to the RS485 two lines, Data+, Data-, and

between computer and converter is connected one to one. The timing flow Between request packet

and response packet is followed.

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Fig 1.2 RS485 Communication Timing

Packet Recognition Time

The data packet between master[PC] and slave[devices] has the following format. One packet

consists of consecutive data frames, and frames is recognized as the same packet for the

condition where the distance between frames is within 5ms. At least 10ms is required to

distinguish each packet.

Fig 1.3 Packet Structure

Holding Time before transmitting Request Packet

After receiving the data from meter, at least 10ms[particulary 13msec in 57600bps] is required to

send a next request packet.

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Chapter 2 Communication Setup

Communication Wiring

Fig 2.1 Communication Wiring

Pin name Ta[TRX+], Tb[TRX-]

Connector Screw terminal[Pluggable]

Wire 1.25 to 3.5 mm2[ 24 to 14 AWG], Shield twisted pair

Maximum Cable Length 1219m[4000ft]

Maximum Devices/bus 32

Note

UL2919 cable is recommended for communication.

Comm Indicator

Comm LED shows green when the meter is transmitting data.

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Setup

Each of these functions can be accomplished by pressing the Menu, Up, Down, and Enter buttons

on the front panel.

Display mode

View parameter measurements

Setup mode

Configure parameters[wiring, communication, and etc.]

Reset mode

Reset energy, demand, maximum, and minimum.

System mode

View meter system information[meter option, firmware version].

Module mode

View information of module added on rear side of the meter

Note

SETUP LED shows red when selecting Setup, Reset, System, and Module modes.

Setup Mode

In Setup mode, You can setup menus, such as PT/CT ratio, wiring, and communication after

mounting the meter.

Button Functions in Setup Mode

Button

Function

Enter setup mode by pressing the Up and Down buttons at the

same time.

Move to the previous menu screen.

Move to the next menu screen.

Enter setup edit mode to configure the displayed menu value.

 the displayed value blinks†

Exit setup mode and move to display mode.

†Shows that the value of menu item is possible to be changed.

Button Functions in Setup Edit Mode

Button

Function

Blink

Shows that the value of menu item is possible to be changed.

† Increase the value of menu item.

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‡ decrease the value of menu item.

Save the edited value of menu item, and the meter automatically

returns to Setup Mode.

†When pressing at least two seconds, cursor is moved to higher position.

‡When pressing at least two seconds, cursor is moved to lower position.

Note

In setup edit mode, pressing button exits system edit mode and moves to display mode,

without saving the changed value of menu item.

Menu Items

Order

Menu Item

Range

Default

1

PT ratio 0.1 ~ 999.9 1.0

2

CT ratio 1 ~ 5000 10

3

Wiring mode

Single phase 2 wires

Single phase 3 wires

Three phase 3 wires, Open Delta

Three phase 4 wires √

4

Comm address 1 ~ 247

5

Protocol Modbus RTU √

Rootech†

6

Speed[bps] 1200bps

2400bps

4800bps

9600bps √

19200bps

38400bps

57600bps‡

7

Parity bits Even parity √

Odd parity

None parity

8

Stop bits 1 ~ 2 1

†Available only for manufacturer. ‡In 57600bps, after receiving the data from meter, at least 13msecs is

required to send a next request packet. And when writing multiple registers to meter, the size of data word is

limited to 24 words.

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Chapter 3 Modbus RTU Protocol

Accura 3550 supports Modbus RTU.

Packet Field of Modbus RTU

Every modbus packet consists of four fields.

 Slave Address Field

 Function Field

 Data Field

 Error Check Field

Slave Address Field

The slave address field of a Modbus packet is one byte in length and uniquely identifies the slave

device involved in the transaction. Valid addresses range between 1 and 247. A slave device,

when receiving a request packet with the slave address field matching its own address, will

perform the command specified in the packet. A response packet generated by the slave will have

the same value in the slave address field.

Function Field

The function field of a Modbus resquest packet is one byte in length and tells the addressed slave

which function to perform. Similarly, the function field of a response packet tells the master what

function the addressed slave has just performed.

Function[Decimal]

Meaning

Description

03 Read Multiple register Obtains the current value from registers.

06 Write Single register Updates one single register to setup value

16 Write Multiple registers Updates more than a register to setup value

Data Field

The data field of a Modbus request is of variable length, and depends upon the function. This

field contains information required by the slave device to perform the command specified in a

request or data being passed back by the slave device in a response packet. Data in this field is

contained in 16-bit or 32-bit registers. Registers are transmitted in the order of high-order byte

first, low-order byte second. This ordering of bytes is called “Big Endian” format.

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Big Endian Example]]

High order byte = 3A hex

Low order byte = 12 hex

This register is transmitted in the order of 12AB

Error Check Field

The checksum field allows the receiving device to determine if a packet has been corrupted with

transmission errors. In Modbus RTU mode, 1 16-bit cyclic redundancy check[CRC-16] is used. The

sending device calculates a 16-bit value using the CRC-16 algorithm. The calculated value is

inserted in the error check field.

The receiving device performs the same calculation on the entire packet it receives, excepting the

error check field. If the calculated checksum is not equal to the checksum stored in the incoming

packet, transmission errors occurred and corrupted the packet. A bad packet will be ignored by

the receiving device. . See the Appendix A of this document for details of CRC-16 algorithm.

Packet Format

Slave address

Function

Data

Error check

1 byte 1 byte N  2 bytes 2 bytes

Exception Responses

If a Modbus master device sends an invalid command to Accura 3550 or attempts to read an

invalid holding register, an exception response will be generated. The high order bit of the

function code in an exception response is set to 1.

The data field of an exception response contains the exception error code.

Exception Response

Slave address

Function

Exception code

Error check

1 byte 1 byte 1 byte 2 bytes

Exception code

Name

Description

01 Illegal Function Unavailable command in Request Packet

02 Illegal Address Unavailable holding address in Request Packet

03 Illegal Value Unavailable data transfer in Holding Address

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Broadcast Packets

The purpose of a broadcast request packet is to allow all the slave devices to receive the same

command from the master. A broadcast request packet is the same as a normal request packet,

except the slave address field is set to zero.

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Packet Communications

this section illustrates the Modbus functions supported by the meter.

Function 03: Read Holding Registers

To read meter parameter values, a Master must send the slave device a Read Holding Registers

request packet. The Read Holding Registers request packet specifies a start register and a number

of registers to read.

Starting Address is a relative address according to register 40000[40001=0, 40002=1, 40101=

100, and etc.]. refer to Appendix B for CRC.

Request

Slave

Function

Starting address

Word count

Error check

03

1 byte 1 byte 2 bytes 2 bytes 2 bytes

Example]

A meter is configured as a Modbus slave device with slave address 1. A phase voltage has the

address 40101, and B phase voltage 40102. register 40101 is numbered as 100 when

transmitted.

slave address = 1, starting address = 64, word count = 2, crc high = 85, crc low = D4

Slave

Function

Starting Address

Word Count

Error Check

01 03 00 64 00 02 85 D4

Response

Slave

Function

Byte Count

Data Word 1

---

Data Word N

Error Check

03

---

1 byte 1 byte 1 byte 2 bytes

---

2 bytes 2 bytes

Data word represents the data required in the request packet. Byte count is two times word cout.

Example]

Slave device with address 1 has A phase voltage= 1A1B, B phase voltage= 223B.

slave address = 1, byte count = 4, crc high = D4, crc low = 5F

Slave

Function

Byte Count

Data Word 1

Data Word N

Error Check

01 03 04 1A 1B 22 3B D4 5F

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ROOTECH ACCURA 3550 Communication User Guide

ROOTECH ACCURA 3550 Communication User Guide

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