Application of Mitsubishi Q Series PLC Analog Output Module in Controlling Inverters

MitsubishiQSeriesPLCAnalog Output Module for Controlling Inverters

Implementing0-50Hz precise speed control solutions

Application Overview

In industrial automation control systems, using the MitsubishiQSeriesPLCanalog output module to control inverters is a common application scenario. By controlling the inverter output frequency with analog signals (0-10V or 4-20mA), stepless speed regulation of motors can be achieved to meet various process requirements.

This control method is widely used in equipment requiring precise speed control, such as fans, water pumps, conveyors, and machine tools, and has advantages such as high control accuracy, fast response speed, and a wide speed adjustment range.

System Configuration

·PLC Module: Mitsubishi Q Series CPU + Q64DA Analog Output Module

·Inverter: Mitsubishi FR-A800 Series (supports 0-10V analog input)

·Control Signal: 0-10V voltage signal corresponding to 0-50Hz frequency output

·Resolution: 16 bits (0-4000 digital value corresponding to 0-10V output voltage)

·Conversion Speed: 80μs/ channel (Q64DA)

·Accuracy: ±0.1% (ambient temperature 25±5℃)

Wiring Scheme

Q64DA Module Channel 1 Output V+: Voltage output positive COM: Common terminal I+: Current output positive

FR-A800 Inverter Analog Input 2: Frequency setting positive input 5: Common terminal 4: Current input positive

Voltage Output Wiring Instructions: Connect the Q64DA module’s channel 1 V+ terminal to the inverter’s terminal 2, and connect the COM terminal to the inverter’s terminal 5.

Current Output Wiring Instructions: Connect the Q64DA module’s channel 1 I+ terminal to the inverter’s terminal 4, and connect the COM terminal to the inverter’s terminal 5.

Notes: Use shielded twisted pair cables for connections, with the shield grounded at one end to avoid parallel wiring with power lines.

Parameter Configuration

Q64DA Module Parameter Settings (GX Works2)

1. Open GX Works2 software, create a new project, and select the correct PLC model

2. In “Parameters” → “PLC Parameters” → “I/O Allocation Settings”, allocate the module position (e.g., slot 0)

3. Double-click the module position to enter the intelligent function module settings

4. Set channel 1 output range to 0-10V

5. Set the alarm output function to “None” (based on actual needs)

6. Set the conversion speed to “High Speed” (80μs/channel)

7. Set the output characteristics for each channel such as CH1, CH2, etc.

8. Write the parameters to the PLC and restart to make them effective

Inverter Parameter Settings (FR-A800)

Parameter Number	Parameter Name	Setting Value	Description
Pr.1	Upper Limit Frequency	50Hz	Set maximum output frequency
Pr.2	Lower Limit Frequency	0Hz	Set minimum output frequency
Pr.7	Acceleration Time	5-10s	Set according to load characteristics
Pr.8	Deceleration Time	5-10s	Set according to load characteristics
Pr.73	Analog Input Selection	0 or 1	0: 0-10V input, 1: 0-10V input (negative logic)
Pr.79	Operation Mode Selection	2	External / PU switching mode
Pr.125	Frequency Setting Gain	50Hz	Frequency corresponding to maximum analog input
Pr.902	Frequency Setting Voltage Offset	0V/0Hz	Frequency corresponding to analog input of 0V

Programming Example:0-50Hz Inverter Control

Example 1: Basic Frequency Control Program

Convert the frequency value set in D100 (0-50Hz) to analog output:

// Frequency–Voltage Conversion Formula: Digital Value = (Frequency Setting Value / 50) × 4000

// Set module starting address toX/Y0

// Read the set frequency value (0-50Hz)

MOV D100 D0

// Limit frequency range to0-50Hz

CMP D0 K0

// CompareD0 with0

BLT LIMIT_LOW

// If less than0, jump to lower limit handling

CMP D0 K50

// CompareD0 with50

BGT LIMIT_HIGH

// If greater than50, jump to upper limit handling

BRA CONVERSION

// Jump to conversion handling

// Lower limit handling: set value to negative, force to0

LIMIT_LOW:

MOV K0 D0

// Set value to negative, force to0

BRA CONVERSION

// Jump to conversion handling

// Upper limit handling: set value exceeds50, force to50

LIMIT_HIGH:

MOV K50 D0

// Set value exceeds50, force to50

// Frequency conversion to digital value:D0(Hz) → D1(Digital Value)

// 50Hz × 80 = 4000, 0Hz × 80 = 0

CONVERSION:

MUL D0 K80 D1

// D0 × 80 = D1 (because50Hz corresponds to4000, so eachHz corresponds to80 digital values)

// Output to analog module channel1

MOV D1 Y0

// Output digital value to module

Example 2: Inverter Program with Acceleration and Deceleration Control

Implement a smooth acceleration and deceleration process to avoid motor impact:

// Variable Definitions:

// D100: Target Frequency (0-50Hz)

// D101: Current Frequency

// D102: Acceleration Time (Unit: 100ms)

// D103: Deceleration Time (Unit: 100ms)

// Main Program

MAIN:

CALL ACC_DEC_CONTROL

// Call acceleration and deceleration control subroutine

CALL FREQ_CONVERSION

// Call frequency conversion subroutine

RET

// Acceleration and Deceleration Control Subroutine

ACC_DEC_CONTROL:

CMP D101 D100

// Compare current frequency with target frequency

BEQ EXIT_ACC_DEC

// If equal, exit

BLT ACCELERATION

// If current frequency is less than target frequency, accelerate

BGT DECELERATION

// If current frequency is greater than target frequency, decelerate

// Acceleration Process

ACCELERATION:

ADD D101 K1 D101

// Increase by1Hz

CMP D101 D100

// Check if target is reached

BLE ACC_DONE

// If less than or equal to target, continue

MOV D100 D101

// Prevent exceeding target value

BRA ACC_DONE

// Deceleration Process

DECELERATION:

SUB D101 K1 D101

// Decrease by1Hz

CMP D101 D100

// Check if target is reached

BGE DEC_DONE

// If greater than or equal to target, continue

MOV D100 D101

// Prevent going below target value

BRA DEC_DONE

ACC_DONE:

DEC_DONE:

EXIT_ACC_DEC:

RET

// Frequency Conversion Subroutine

FREQ_CONVERSION:

// Convert frequency value to digital value

MUL D101 K80 D200

// Output to analog module

MOV D200 Y0

// Channel 1 output

RET

Example 3: Buffer Memory Write Program Using TO Instruction

Use the TO instruction to directly write to buffer memory, improving program readability and execution efficiency:

// Use TO instruction to write to buffer memory

// Module starting address: 0 (based on actual I/O allocation settings)

// Buffer memory address: CH1 output data address is 0

// Frequency conversion calculation

MOV D100 D0

// Read the set frequency value

MUL D0 K80 D1

// Convert to digital value

// Use TO instruction to write to buffer memory

TO H0 0 D1 1

// H0: Module starting address, 0: Buffer memory address, D1: Data to write, 1: Number of points to write

// Set output mode (if needed)

MOV K1 D10

// Set output mode to 1 (normal output)

TO H0 20 D10 1

// Write output mode settings (buffer memory address 20)

Application Notes

Important Reminder: Please pay attention to the following matters in practical applications:

·Electrical Safety: Ensure the device is powered off before electrical wiring, and have it operated by professionals

·Shielding and Grounding: Use shielded cables to connect analog signals, with the shield grounded at one end to avoid parallel wiring with power lines

·Signal Interference: Set appropriate carrier frequency in inverter parameters to reduce electromagnetic interference

·Program Protection: Add frequency limit functions in the PLC program to prevent exceeding the inverter’s allowable range

·Startup Protection: Consider the current impact during motor startup and set appropriate acceleration time

·System Safety: Add emergency stop functions to the system to ensure operational safety

·Regular Maintenance: Regularly check the accuracy of analog outputs and calibrate when necessary

·Parameter Backup: Save the parameter settings of the inverter and PLC for easy fault recovery

Troubleshooting Common Issues

Problem Phenomenon	Possible Cause	Solution
No Output	Module power not connected, wiring error, parameter setting error	Check module power, wiring, and parameter settings
Unstable Output	Signal interference, poor grounding, shielding not connected	Check grounding and shielding, eliminate interference
Incorrect Output Value	Conversion formula error, parameter setting error	Check conversion formula and parameter settings
Inverter Not Responding	Inverter parameter error, operation mode setting error	Check inverter parameters and operation mode
Motor Vibration or Noise	Improper frequency setting, mechanical resonance	Adjust frequency settings, avoid resonance points

Frequency–Voltage–Digital Value Correspondence

Frequency(Hz)	Voltage(V)	Digital Value
0	0	0
12.5	2.5	1000
25	5.0	2000
37.5	7.5	3000
50	10.0	4000