Mitsubishi Electric and Drives: A Complete Guide to Industrial Motion Control
Created on 05.18
Mitsubishi Electric is a global leader in industrial automation. Its drive products, including variable frequency drives (VFDs) and servo systems, are widely used in factories around the world. These drives control the speed, torque, and position of electric motors, enabling precise motion in applications such as conveyors, robots, machine tools, and packaging equipment. Understanding how to select, install, and troubleshoot Mitsubishi drives is essential for maintenance engineers and automation technicians.
This article provides a practical overview of Mitsubishi Electric's drive family, focusing on the popular FR series of variable frequency drives and the MR-JE, MR-J4, and MR-J5 series of servo amplifiers. It covers basic fault analysis, common error codes, and best practices for system reliability.
- Overview of Mitsubishi Drive Products
Mitsubishi Electric organizes its drive products into two main categories: general-purpose inverters (VFDs) and AC servo systems.
General-Purpose Inverters (FR Series)
The FR series includes the FR-A800, FR-F800, FR-E800, and FR-D700 models. These drives control standard induction motors or permanent magnet motors.
FR-A800: High-performance drive for advanced applications such as cranes, elevators, and extruders. It supports position control and high-speed communication.
FR-F800: Designed for fans, pumps, and blowers. It focuses on energy savings and constant torque control.
FR-E800: Compact drive for general factory automation. It offers built-in Ethernet communication and safety functions.
FR-D700: Basic, cost-effective drive for simple speed control applications.
AC Servo Systems (MR-J Series)
The MR-J series includes servo amplifiers and compatible servo motors. These provide closed-loop position, speed, and torque control.
MR-J5: The latest generation. It supports CC-Link IE TSN (Time-Sensitive Networking) for high-speed, real-time motion control.
MR-J4: High-performance servo with 26-bit encoder resolution. Suitable for precision machining and robotics.
MR-JE: Standard servo for general automation tasks. It is easy to set up and cost-effective.
- Basic Fault Analysis for Mitsubishi Drives
When a Mitsubishi drive stops working or shows an alarm, the first step is to read the error code from the drive's display panel. Most FR series inverters use a seven-segment LED display, while MR-J series servos use a combination of LEDs and a digital display.
Common Fault Categories
Mitsubishi drive faults generally fall into four categories:
Overcurrent and Short Circuit (FR series: E.OC1, E.OC2, E.OC3; MR-J series: AL.32, AL.33)
These errors occur when the drive detects excessive current on the output side. Causes include:
Short circuit in the motor winding
Ground fault in the motor cable
Acceleration or deceleration time set too short
Mechanical load stuck or jammed
Overvoltage and Undervoltage (FR series: E.OV1, E.OV2, E.OV3, E.UVT; MR-J series: AL.10, AL.12)
Overvoltage often happens during deceleration. The motor regenerates energy back to the drive, raising the DC bus voltage. Undervoltage indicates low input power or a weak power supply.
Overload and Overcurrent Trip (FR series: E.THM, E.THT; MR-J series: AL.50, AL.51)
These errors mean the motor has drawn too much current for too long. The cause is usually excessive mechanical load or a motor that is undersized for the application.
Communication Errors (FR series: E.OP1; MR-J series: AL.E6, AL.E7)
The drive cannot communicate with the PLC or controller. Check the communication cable, baud rate settings, and station number assignment.
- Reading and Clearing Errors
Every Mitsubishi drive stores error history. For FR series inverters, you can access the parameter group that contains the last eight faults. For MR-J series servos, the software MR Configurator or the digital display shows the alarm history.
To clear a fault:
First, remove the cause (repair the short, reduce the load, etc.).
Then, reset the drive. On FR series, press the STOP/RESET key or cycle power. On MR-J series, apply the reset signal or cycle power.
Important: Cycling power without fixing the root cause will make the alarm return immediately.
- Troubleshooting Matrix for Common Faults
Use this matrix to quickly identify and fix common Mitsubishi drive problems.
Symptom: Drive displays E.OC1 during acceleration
Likely Cause: Acceleration time too short or motor short circuit
Action: Increase Pr.7 (acceleration time). Check motor insulation.
Symptom: Drive displays E.OV1 during deceleration
Likely Cause: Deceleration time too short or no braking resistor
Action: Increase Pr.8 (deceleration time). Add a braking resistor or regeneration unit.
Symptom: Drive displays E.THM (overload)
Likely Cause: Mechanical binding or motor undersized
Action: Inspect gearbox and bearings. Measure motor current. Consider larger motor.
Symptom: Servo shows AL.32 (overcurrent)
Likely Cause: Motor cable shorted to ground
Action: Use megohmmeter to test motor winding resistance. Replace cable if damaged.
Symptom: Servo shows AL.E6 (emergency stop)
Likely Cause: Emergency stop switch activated or wiring open
Action: Check emergency stop circuit. Verify 24V supply to the emergency stop relay.
- Preventive Maintenance for Mitsubishi Drives
Regular maintenance reduces unexpected downtime. Follow these guidelines for Mitsubishi drives.
Environment
Keep the drive clean and dry. Dust and humidity shorten the life of capacitors and fans. The recommended ambient temperature is 0 to 50 degrees Celsius. Derate the drive current by 50 percent if operating above 40 degrees Celsius.
Cooling Fans
Cooling fans have a typical life of 3 to 5 years in continuous operation. Replace the fan when noise increases or when the drive displays a fan life alarm (FR series: E.FN).
DC Bus Capacitors
The main DC bus capacitors age over time. If the drive has been stored for more than two years, apply low voltage gradually (a process called reforming) before full power operation. Refer to the Mitsubishi manual for the reforming procedure.
Tightening Terminals
Vibration can loosen power terminals over time. Check and retorque main power terminals every year. Loose terminals cause overheating and intermittent faults.
Parameter Backup
Always save drive parameters to an external device or computer. For FR series, use the parameter unit (FR-PU07) or FR Configurator software. For MR-J series, use MR Configurator. Without a backup, a drive failure forces you to reprogram all settings from scratch.
- Common Myths About Mitsubishi Drives
Myth: "A drive that worked for ten years should be fine."
Reality: Electrolytic capacitors dry out. Fans wear out. After 7 to 10 years, consider proactive replacement, especially on critical machines.
Myth: "We can use any cable for the motor."
Reality: Mitsubishi drives produce high-frequency switching noise. Use shielded cable for motor leads, and keep the cable length under the maximum specified in the manual (typically 30 to 100 meters depending on drive size).
Myth: "Resetting the error is enough."
Reality: A recurring alarm always has a root cause. Resetting without investigation invites more downtime.
Mitsubishi Electric drives are reliable workhorses of modern industry. However, even the best equipment requires correct installation, regular maintenance, and systematic troubleshooting. By learning the common error codes, understanding the fault categories, and following the preventive maintenance schedule outlined in this article, engineers can keep production lines running and minimize costly stoppages.
Whether you work with FR series inverters or MR-J series servos, the principles remain the same: observe the error, identify the cause, fix the root problem, and document the solution. This disciplined approach separates a professional troubleshooter from a simple alarm clearer.
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