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What servo should I choose and why?

Bryon Sol


Okay, so here's where I admit that I was intimidated by servos for years in my early career.   Why?  Because they were expensive and I was afraid to get it wrong, plus there were so many options that I was overwhelmed.

But in terms of Mitsubishi Servos it's actually pretty simple.  You are either using an IO controlled servo, or a networked servo.  So how do we know which is which?

Starting with the amplifiers, let's break down an example part number:  

The MR simply means it's a servo amplifier meant for general automation.
The J4 is the series of amplifiers.
The 20 means it's a 200 Watt amplifier.  This is the power it can deliver to the servo motor.
The A indicates the control type, in this case digital I/O control, we'll discuss this much more later.
The 1 after the A indicates that this is a 100V amplifier, meaning the power to the amplifier is 100VAC (100-120 works).
The RJ indicates that this amplifier has a Safe Torque Off functionality, earlier versions did not have this functionality and didn't have the RJ suffix.

There's a little more to this than what's shown above but in general this is what we are looking at when it comes to picking an amplifier.  They all start with MR, then a series (J4, JE, JN, J5, JET etc), then a power rating, a control type, a voltage modifier may or may not be present (1=100V, 4=400V, nothing = 200V), and finally other modifiers as necessary for special features.


The first thing I like to look at when picking an amplifier is actually the control type.  You will find a few control types with Mitsubishi Servo Amps, basically there are two main categories with a couple of sub categories. Servo amplifiers are either digitally controlled (inputs and outputs) or network controlled.  Here are the various Control Types you'll see in the Mitsubishi Line Up:

A Type Amps (example MR-J4-20A1-RJ)
These are Digital IO Control, this can be pulse and direction.  Some have table mode where you program positions inside the drive and call them via digital IO and some have the ability to do Program Mode where a script can run in the drive.  No matter which mode you use (pulse and direction, table or program) the drive is controlled by 24V digital IO signals wired to the front of the drive.

B or BF Type Amps (example MR-J4-70B-RJ, MR-JE-200BF)
These drives work on an SSCNET Fiber Optic Control Network.  These get their control signals from a Motion Control Module connected to your PLC.  All series of Mitsubishi PLCs have various cards that can control these drives, you can use an FX3, FX5 (iQ-F), L Series, Q Series or R Series (iQ-R) PLC with an appropriate motion card to drive these.  Some of the advantages include the fact that Fiber Optic networks are not affected by electrical noise, they are very fast and the motion cards can do coordinated motion, so if you need to do 2-axis linear motion or 2-axis circular motion or even more complex motions like camming etc, these amplifiers can be controlled by a motion card in a coordinated fashion.  The MR-JE series can be purchased as MR-JE-xxxB or MR-JE-xxxBF the F adds Safe Torque Off (STO) functionality to the drive.

C Type Amps (example MR-JE-40C)
These drives work on the CC-Link IE Field Basic network.  This is a low cost option for point-to-point control.  All of the FX5, L-Series, Q-Series and R-Series PLCs with built-in Ethernet can control the servos directly from this built-in Ethernet port (some older systems may not be able to do this, check for the CC-Link IE Field Basic marking on the front of the PLC).  The big advantage here is cost.  If you need to do simple point to point moves, or speed control, or torque control, these amps can do it without a motion card being needed.

G Type Amps (example MR-JET-40G)
These drives work on an Ethernet network and there are a few sub options.  The straight G type are meant for Mitsubishi control and will work on CC-Link IE TSN networks for coordinated motion, but they can also function on CC-Link IE Field Basic for a low cost solution for point-to-point uses.  The sub-type G-N1 are EtherCAT controlled drives.  There are also GF type amps (MR-J4-70GF-RJ for example) that are ethernet based that can work as either CC-Link IE Field (not TSN) or CC-Link IE Field Basic.

TM Type Amps (example MR-J4-40TM-EIP)
These drives work on an Ethernet network and can be purchased as either ECT for EtherCAT, EIP for Ethernet/IP or PNT for PROFINET compatibility.  You can get application notes and how-to guides from Mitsubishi which will show you how to use these drives with third party PLCs such as Beckhoff, Allen-Bradley and Siemens among others.

Amplifier Series

As of Spring 2023 here are the current families of Servo Amplifiers and general info about them:

MR-JN Series
These are only pulse and direction and are designed for simple applications.  They are available in 100V and 200V systems with a variety of motors and output powers up to 400 Watts.

MR-JE Series
These are available as A, BF and C type control and are 200VAC up to 3kW.  They have a wide variety of control methods and are a lower cost option with 17-bit encoder resolution for general servo applications.

MR-J4 Series
These were the top of the line servo series until the MR-J5 series came out.  With 24VDC/48VDC controllers, 100VAC Single Phase up to 400VAC three phase options and from 10 Watt motors up to 55kW, this series provides options for motors and amplifiers for almost any application.  And with A, B, GF and TM control options, almost any type of control is possible with this series.  On top of this with 22-bit encoders on the motors precision was unsurpassed until the J5 series came out.

MR-JET Series
These are network only amplifiers working on G and G-N1 networks.  Similar to the JE series being the lower cost alternative to the J4 series, the JET series is the lower cost alternative to the J5 series and is the step up from the JE series.  With 200VAC and 400VAC options with power up to 3kW and 22-bit resolution on the encoders on the motors, this series represents a fantastic price/performance option.

MR-J5 Series
These are the top of the line amplifiers from Mitsubishi with A type and G type options allowing pulse train control or CC-Link IE Field TSN as well as EtherCAT with the G-N1 versions.  The series is still expanding but current operates on 200VAC or 400VAC from 100 Watt output to 22kW.  And with 26-bit resolution on the encoders the precision of control has reached new levels never seen before.


So which one do I choose?

For lower cost solutions, you are typically looking at pulse/direction systems.  These are your A Type amplifiers.  So stick with the MR-JN or MR-JE series, or even the MR-J4 or MR-J5 for higher performance.  But understand that unless your control system can do multi-axis pulse and direction, most likely this is single actuator point-to-point motion only.

For more control, step up to networked devices.  For instance, with Mitsubishi PLCs with built-in CC-Link IE Field Basic you can get positional feedback, alarm info etc over the network.  So going to an MR-JE-C, MR-J4-GF, MR-JET-G, or MR-J5-G allows more interaction, but still lower cost because you don't have a motion control card on your PLC.

For the best control, add a motion card to match the network of your drive and either go the the B type amplifiers like the MR-JE-BF, or MR-J4-B series, or move up to CC-Link IE Field with the MR-J4-GF series.  Or for top end applications move to CC-Link IE TSN and go with MR-JET-G or MR-J5-G series amplifiers.

Mitsubishi also provides servo sizing tools to help you pick the right motor type (low inertia, mid inertia etc) and the right wattage for your loads.

If you need any assistance picking or sizing your servo, don't hesitate to reach out to your sales rep for support!




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