How to Upgrade from Yaskawa Sigma-II to Sigma-7

How to Upgrade from Yaskawa Sigma-II to Sigma-7

Greg Haley | September 6th, 2018

It doesn’t matter what industry you are in, at some point in time a product you’ve used for years will go obsolete and you will have to upgrade. Fortunately for Yaskawa servo users, this path to upgrade can be straightforward and easier than expected. This is thanks to Yaskawa consciously designing their latest generation products and because of the services Cross Company provides.

As an example, take a recent project Cross Company did that involved moving a 300+ axis project from Yaskawa Sigma-II to Sigma-7. The machines had been in service for 10+ years running on the Sigma-II servo drives and motors platform. As these parts became obsolete, the drives were simultaneously reaching the end of their useful lives and needed to be replaced. Yaskawa Transition Guides do a great job of outlining the part number and cable conversions. This, coupled with the engineering and kitting services of Cross Company, made the transition very easy for the customer.

In this particular example, it wasn’t possible for the customer to go directly from Sigma-II to Sigma-7. The conversion was made in stages over a few years, using Sigma-V as a stepping stone to Sigma-7.

Features and Benefits of Yaskawa Sigma-7

Phase 1 - Replace Sigma-II Drives, Operate with Sigma-II Motors and Sigma-V Drives

To cross the drives over to the Sigma-V platform there are three main concerns:

  1. Can the new drives handle all of the requirements of the old motor? This is easily remedied by checking the Sigma-II to Sigma-V conversion guide from Yaskawa and matching the Sigma-II to drive with the equivalent Sigma-V drive.
  2. How do I mount the new drive? The Sigma-II drives and Sigma-V drives have different mounting configurations. Usually, it is not desirable to completely redesign the electrical panel. In this case, Cross Company designed and provided custom, machined adaptor plates to allow the Sigma-V drives to bolt in right where the Sigma-II drives were.
  3. Do I have to run new cables? As one might expect, when you are looking at 300+ axis, there are a lot of cables. Fortunately, Yaskawa makes adaptor cables that allow the old Sigma-II motor and encoder cables to work with the Sigma-V drive. Instead of redoing all of the cabling for each axis, insert an adaptor between the end of the old cables and the new drive.

Now that the physical and electrical concerns are addressed, the last thing to do is move the set parameters of the old drives to the new drives. This can be extremely tedious when replacing 300+ drives. For this particular system, Cross Company received the customer’s new drives from Yaskawa and flashed the software on all of them to match how the old drives were configured. Each drive was labeled to match the axis labels on the customer machine. This was so the labels on the drives matched the customer drawings and there was no confusion on which drive went where.

All that was left for the customer to do was take out the old drive, mount the new Sigma-V drive with adapter cables, and run the tuning. With the work Cross Company did upfront, the customer was able to replace drives on approximately 22 axis per day.

Phase 2 - Replace the Sigma-II Motors, Operate with Sigma-7 Motors and Sigma-V Drives

To cross the motors over to Sigma-7, there are six main concerns:

  1. Are the new motors capable of providing enough torque to meet the speed, load, and acceleration requirements? In the Sigma-II to Sigma-7 transition guide, Yaskawa outlines which Sigma-7 motor is the upgrade equivalent for the Sigma-II. This guide was used to select the new model number in the Sigma-7 family.
  2. Are these motors the same size and form factor as the Sigma-II? In most cases, they are not. The dimensions vary slightly and it is necessary to verify that the new dimensions of the motor will fit in the machine.
  3. What about inertial matching? Most of the Sigma-7 motors have a different inertia value then their Sigma-II equivalent. Therefore, it is necessary to check the inertial values of the new Sigma-7 motor and make sure it will work in the application.
  4. I am using a SimgaV Amp with a Sigma-7 motor, is there anything I should look out for? In short, this can be done but isn’t an officially supported configuration from Yaskawa. The biggest concern is tuning the drive and motor combination. The recommended path forward is to test the configuration on a system before doing a full conversion and install.
  5. Does braking work the same on Sigma-7 as it did on Sigma-II? No. On the Sigma-II drive, the brake coil was 90 VDC. On Sigma-7, it is 24VDC. The voltage control for the brake will need to be changed for the new Sigma-7 motor brake.
  6. What about my cables? Since the configuration isn’t officially supported from Yaskawa, there is not a path to use Sigma-II cables with Sigma-V drives and Sigma-7 motors. The requirement is to replace all of the encoder and power cables. In this case, the cables that would go with a Sigma-7 motor/amp combination are used with the Sigma-V/7 combination.

For this particular customer, they were also replacing the mechanics at the same time they replaced the motors. Cross Company was able to mount to the motors to the new actuators and ship them to the customer as a ready to drop in axis. This significantly cut down on the amount of work done by the customer and thus the amount of downtime on the machine.

Phase 3 - Replace the Sigma-V Drives, Operate with all Sigma-7 Motors and Drives

At this point, all of the motors are already Sigma-7 and both encoder and power cables have been converted to Sigma-7. The last step is to move to the Sigma-7 drive. To do this, the easiest way is to select the Yaskawa drive that is recommended for the Sigma-7 motor on each axis. This will ensure the motor and cables work the particular drive. From here on, there are no concerns about power/current capability or drive tuning because it was a preferred and recommended configuration.

The parameters had to be transferred from the old Sigma-V drive to the new Sigma-7. Cross Company was able to do this before it ever reached the customer’s receiving dock. All the customer had to do was remove the old Sigma-V drive, bolt in the new Sigma-7 drive, connect the cables, and tune.


There are several paths to upgrade from Sigma-II or Sigma-V to Sigma-7. This is one example of how a Cross Company customer did it to satisfy their immediate and future needs while minimizing downtime. There is no doubt that some applications will take a much faster, direct path to an entire Sigma-7 system.

Regardless of the path taken, Cross Company is able to help with everything from part number conversion, kitting, to tuning assistance. By working with Cross Company, this customer was able to save a significant headache and downtime because of the work we were able to do ahead of the product actually reaching them. From the initial requirement discussion to the final axis installation, we worked closely with them to make sure the transition was painless and successful.

If you have a Yaskawa servo system that you’d like to upgrade to Sigma-7, contact Cross Company for a consultation.

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Greg Haley


Greg received his degree in Mechanical Engineering from the University of Florida. He has spent his entire professional career working in the automation industry, including as a consultant building an automated manufacturing system, 4 years as a Field Engineer in the automated test industry, and most recently, a Motion/Robotics solution provider with Cross Company.