Dynamic manufacturers who seek to keep pace with changing markets and shifting customer expectations are wise to upgrade their variable frequency drive technology. Moving to new tech without a plan, however, is a recipe for disaster. To aid those who desire improved processes and expanded capabilities, I offer eight steps to effective drive migration.

About Migration

Migration is the process by which one variable frequency drive platform is exchanged for another and is often how many facilities move to more advanced forms of automation. Once plans for migration have been made and systems are shut down for a replacement procedure, two predominant goals must be met for an effective “switch day:” minimized downtime and establishment of system control (both old and new).

Rockwell Automation has produced a number of migration guides that explain key differences between legacy and new drive platforms.  Using these guides in conjunction with the eight steps presented below is encouraged.

Article in Brief

Step 1: Understand the Reasons for Migration

Whether it be a transition to Ethernet networking, a move to more advanced processing technology, or simply a desire to no longer operate with obsolete tech, there are many reasons to migrate.  Nevertheless, the specific reason for migration at a facility must be clearly understood by those involved.  Material selection, installation procedures, and startups depend on a clear understanding of what is driving the move to new technology.  For example, if a manufacturer needs safety over ethernet, then a PowerFlex 755 should be selected over a PowerFlex 753.  This is a choice that might not be made if horsepower alone is considered.

Additionally, if the reason for the migration is secondary to another plan–a plant-wide move to Ethernet or an analytics platform for instance–then a deeper take on connectivity may be needed:  is device-level ring more efficient given the number of devices that will have to be connected, or is a single end connection sufficient?  A thorough understanding of the reasons for the migration should clarify all possible configuration questions.

Step 2: Assess Control Wiring Needs

Control wiring voltage, count, and interconnections must be assessed thoroughly if both goals of a successful migration are to be met.  IO wiring easily consumes most of the time spent in a migration if not considered properly.  Systems slated for change over should have their wiring diagrams studied in advance of actual replacement operations.  If no wiring diagrams exist, then time should be spent routing all relevant wired connections.

Once system wiring has been assessed, a new drive with equivalent wiring capabilities should be chosen.  For those situations where a miss-match in IO voltage or count is unavoidable, interposing relays often serve as a solution.  It must also be said that a move to a different drive platform than originally intended due simply to IO needs is often well worth the consideration as it will ensure an effective re-establishment of process control—something that should not be compromised simply to lower first costs.

Step 3: Evaluate Complementary Devices

Variable frequency drives are often paired with complementary devices:

  • Circuit protection devices
  • Line and Load Reactors
  • VFD Cable
  • Harmonic mitigation devices
  • Dynamic brakes

For new construction, the exact operating circumstances of the VFD will determine the applicability of each of these complements; however, the continued use of existing complementary devices with new VFD technology must be considered carefully for an effective migration.  Reactors and dynamic brakes may need to be replaced along with the old drive that they serve.  Moreover, new VFD platforms may have complementary devices either built-in or no longer needed, as would be the case with a move from a PowerFlex 700H to a 755TR.  The 755TR is capable of regeneration and would not need any existing dynamic brakes that may be a part of the 700H package it replaces.

Allen Bradley has produced a number of migration guides that identify complementary equipment for both old and new drive technology.  All VFD migration plans between AB drives should include a review of these documents.  

Step 4: Evaluate Option Cards and Accessories

Undertaking the first three steps will provide the answers needed for the fourth:  the selection of option cards and accessory items needed to ensure that the new drive can meet existing or new automation needs.  Naturally, IO voltage and count will play into the choice of IO option cards, and the overall reason for the migration often highlights the need for Ethernet modules.  The need for complementary items such as dynamic brakes can also affect internal drive configuration.

Moving from one manufacturer to another often precludes the reuse of accessory items.  When moving within one manufacturer’s portfolio, however, reuse does become possible.  Regarding the PowerFlex series of drives, the HIM modules for the 4-series and 5-series are the same.  They also use the same bezel and DSI cable.

In contrast, the 7-series and the 750 series do not use the same HIM module, but they can both use the 20-COMM-E ethernet card with some caveats:  The 753 or 755 can only incorporate the 20-COMM-E when it is paired with the 20-750-COMM-F1 or the 20-750-20COMM.  Furthermore, if moving to the 750 series, the 20-750-ENETR comes highly recommended for Ethernet connections as it is capable of DLR connectivity and has 4 more data links compared to the 20-COMM-E.

Step 5: Assess Spacing and Dimensions

Naturally, different variable frequency drives have different dimensions.  Dimensional differences need to be assessed both for overall footprint and airflow requirements.  The migration guides for Allen Bradley VFD’s provide detailed information regarding dimensional differences between older and newer drive platforms.  

When facing a difference in dimensions two options present themselves:  panel re-arrangement or a change of enclosure.  Replacing an entire panel can be expensive, but it may be the best option when considering both goals of minimized downtime and the establishment of control. 

Step 6: Examine Power Wiring

VFD’s can accept a range of conductor sizes for their main AC input and motor output.  It is generally the case that existing power wiring is applicable to both the existing and replacement VFD; however, a check of wiring requirements should be made as a miss-match in wire sizing may cost hours of unplanned for downtime.

Moreover, if the original wiring is THHN, migration offers an excellent opportunity to move to VFD Cable.  THHN is a poor choice for motor-wire from a VFD because of the higher voltages produced by a VFD versus a full voltage starter.  VFD cable eliminates harmful corona effects that lead to damaged wiring due to its high insulation levels.  VFD cable will also suppress common-mode noise, a frequent cause of grief for variable frequency drive operators.

Step 7:  Program Parameters

Parameters are sets of data contained within a variable frequency drive that determine its operation.  Repeating existing drive parameter settings in a replacement unit will be necessary for the establishment of control.  To minimize the time spent in programming a new drive, Rockwell offers Connected Components Workbench software (CCW).

CCW is the current software of choice for drive programming and configuration, providing easy access to parameter settings and startup wizards.   Each drive’s parameter settings are held in a file for future reference or re-use.  Also, it is possible to create a parameter file independently of the presence of a drive.  This allows for pre-configuration before material delivery coupled with simplified commissioning.

For those more familiar with Drive Executive or other programs, it should be noted that while these programs will work with legacy systems and the 4 and 7-series, their functionality with the 5-series and newer drives is limited.

If Studio 5000 is in play, then configuring a new drive is just as easy as with CCW.  The add on profile for your drive can be created in advance of arrival.  Once connected and configured with the appropriate IP address, the PLC will automatically program the newly installed drive with the desired parameter settings.

Whether using Studio or CCW, it will be necessary to do parameter research. Different drives use different parameter numbers and names for the same functions.  Time spent understanding and accounting for these differences in advance of a shutdown is time well spent.

Step 8: Reprogram PLC’s as Necessary

PLC’s and DCS systems are often in control of variable frequency drives.  When migrating from one drive to another, it will be necessary to reprogram associated control systems accordingly.  Taking advantage of Rockwell Automation’s Premier Integration will significantly reduce time spent programming for migration, as the new drive will port into the Studio 5000 environment with premade tags associated with drive parameters.  This feature saves significant amounts of programming time as a result.

If existing logic is to be re-used for the new drive, then the following steps may be taken to transition logic from one drive to another in the Studio 5000 environment:

  • Save a copy of the logic program as a backup if issues arise with the new program.
  • Remove the old drive from the ethernet connection tree.
  • Create an add on profile for the new drive with its IP address.
  • Name your new drive the same name as the old drive.

These steps should result in Studio transferring over your old logic to your new drive seamlessly.  Take care, however, as the new drive may scale certain parameters differently and may have different tag names for the same parameters.

If the above method is not preferred, or if the original drive is not a Rockwell product, then a more painstaking approach to drive integration will be needed.  Going to each element within the logic structure and redirecting it to the new VFD will take time, but is a tried and true method of migration programming.  Patience in this is key, and the ability to save and copy logic programs should be taken complete advantage of. 

AIMM Services

In addition to the 8 steps, AIMM services is available for modernization assessments and drive startups.  AIMM will help their client determine a migration plan and will also help properly specify material.  Feel free to click this link and make contact.

Migration is done to improve overall equipment effectiveness, profitability, and capability.  The eight steps above will allow any professional to reach their migration goals with minimized frustration.  Additionally, AIMM Services is here to help manufacturing professionals make the best decisions for their facility.

If you would like to know more about drive modernization or have your own insights to share, feel free to comment, and reach out to your local system specialist.

For more information about drives and drive systems, check out the Variable Frequency Drive Main Help Page