MODBUS Communication between PLC and Delta VFD-V Series AC Motor Drive

MODBUS Communication between PLC and Delta VFD-V
Series AC Motor Drive

  



PLC VFD MODBUS Communication Control Purpose:

  • Repeatedly reading the master frequency and output frequency of
    VFD-V series AC motor drive by MODRD instruction.
  • Setting the drive to run forward in 30Hz by MODRW instruction when
    X0 is pressed.
  • Setting the drive to run in reverse in 20Hz by MODRW instruction
    when X1 is pressed.
  • Stopping the drive by MODWR instruction when X2 is pressed.

MODBUS Parameter Settings for VFD-V Series AC Motor Drive:

Parameter
Set value
Explanation
00-20
1
Master frequency controlled by RS-485 communication.
00-21
0
Digital keypad (KPV-CE01)
09-00
01
Communication address: 01
09-01
9.6
Communication baud rate: 9600.
09-04
02
ASCII mode. Protocol: (7, E, 1).
·       
If AC motor drive cannot run normally due to improper parameters,
users can set P00-02 = 10 (factory defaults) and then set the parameters
according to the above table.
Devices:
Device
Function
X0
Forward
X1
Reverse
X2
Stop
M0
Executing MODRD instruction to read master and output frequency
M1
Executing MODWR instruction to set running direction and
frequency

 Modbus Communication between PLC and VFD Ladder Program:



MODBUS Communication PLC –VFD Program
Description:


·       
Initialize
PLC RS-485 communication port and set the communication format as MODBUS RTU,
19200, 8, N, 2. The RS-485 communication format of AC motor drive should be the
same with PLC.
·       
Reset
D0 and D1 when PLC is powered up so as to ensure the drive is in the Stop
status
·       
When X0
is activated, the drive will run forward (D0 = H12) in 30Hz (D1 = 3000).
·    When X1
is activated, the drive will run in reverse (D0 = H22) in 20Hz (D1 = K2000)
·       
When X2
is activated, the drive will stop. (D0 = H1, D1 = 0)
·      There
are only 4 situations for MODBUS communication: flag M1127 for normal communication
and M1129, M1140, M1141 for communication errors. Counter C0 counts once when
any of the 4 flags is ON. Therefore, the program assures the communication reliability
by monitoring the On/Off status of the 4 flags and performs 2 MODBUS instructions
in order by the value in counter C0.
·    The
master frequency and output frequency stored in D1050 and D1051 will be sent to
D2 and D3.
·  Once PLC starts running,
the read/write actions for AC motor drive will be performed repeatedly
according to [LD=] instructions.

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