As we’ve recently outlined, there are many factors that contribute to medium voltage VFD power cell life. With care and planning (or a preventative maintenance program), your electrical equipment can last a long time. However, there is a stark reality to all electronics: eventually, they all fail. The question many maintenance managers find themselves asking is, “What measures should I take when it comes to extending the life of my medium voltage VFDs?” Depending on your budget, time frame, and stomach for downtime, there are a few different answers to this common question.
Based on our 30 years of experience installing, repairing, and replacing electronics, we can accurately predict when a medium voltage power cell is nearing or beyond its usable life. Electrolytic capacitors, which are present in many different types of power cells, have a usable life of approximately 7-10 years. If your power cell is nearing or past that time frame, it is reasonable to assume it needs attention.
Four options maintenance managers have for maintaining medium voltage drive power cells:
- Refurbish – before they fail
- Repair – when they fail
- Replace – when they fail
- Roll the Dice – do nothing and hope for the best
If your medium voltage drive has not yet failed, refurbishment is the recommended option. Refurbishment involves changing all electrolytic capacitors on all circuit boards, as well as the electrolytic capacitors of the DC bus. It is often less expensive to change out all circuit cards in the power cell to the most updated version instead of changing the capacitors at the component level. If your power cell uses oil-filled capacitors, they may need to be changed as well depending on their age.
Refurbishment is a great option for you if you have a medium voltage drive that is currently running and plan to continue to use the drive for the foreseeable future. However, if the medium voltage drive is scheduled for replacement soon, refurbishment is not a worthwhile investment. Medium voltage power cell refurbishments are the least expensive of the four options. In many cases, spending the money on a refurbishment now can help you avoid spending money on repairs or replacements later. Refurbishing a drive requires it to be down, so this work should take place during a scheduled downtime.
If your medium voltage drive power cell has already failed, repair is a viable option. We at EMA recommend that our customers have a spare medium voltage power cell on hand for when a failure occurs. Doing so allows you to get back up and running quickly. Once you swap out the damaged cell with the spare, you can repair it, then keep it as the new spare. If you do not have a spare available, repair may still be the most time efficient option when your MVD is down AND the manufacturer has no power cells in stock. Situations exist where you are forced to use the repair option because new power cells are no longer made for your particular drive. Fortunately, EMA is well equipped to do rush repairs on medium voltage power cells, even obsolete ones! If you are in dire need of a repair, call our cell repair hotline for immediate assistance.
If your power cell has failed and a replacement is still available to purchase, then this is a viable option, especially if time is critical. Although buying an entirely new power cell has the highest initial cost of the options, it could save you money depending on what downtime costs to you. The majority of medium voltage variable frequency drives are modular in design, allowing you to change power cells in as little as 30 minutes, which could save you thousands in downtime. Unfortunately, for many of EMA’s customers with obsolete medium voltage VFDs, cell replacement is not a viable option because new power cells simply are not being made anymore. For this very reason, EMA keeps many refurbished and tested power cells in stock from obsolete medium voltage VFDs. If your drive is no longer in production and you need to replace a power call, call us to see if we have one in stock.
Roll the Dice (do nothing)
The “do nothing” option is an option that many choose to take. This option is sometimes chosen because of a tight budget. Some choose this option because they already have existing plans to change out the medium voltage VFD soon. If the drive is about to be completely replaced, it is certainly logical to roll the dice and hope your medium voltage drive runs until it is time for it to be replaced. If there are no plans to replace the drive itself, the “do nothing” approach can have catastrophic consequences for your business.
Comparing the Options
EMA’s assessment of the options is based on years of experience installing, repairing, and performing preventative maintenance on medium voltage drives. Our team got together to discuss the options and how each has an impact on our customers. This simple comparison chart demonstrates the results of our discussion.
Drive failures happen, be ready
Medium voltage VFDs are highly reliable, yet there are factors that will cause failures. Drives fail. It’s not a matter of IF, but when. Being prepared by having a refurbished, repaired, or new cell available can relieve stress and reduce downtime. Most EMA customers are in highly competitive industries, where downtime is very costly to their reputation and their bottom lines. Do not let a cell failure be a competitive disadvantage to your company!
EMA is here to help
We’ve seen a lot. We’ve fixed a lot. We invite you to contact us to discuss which option is best for your company. You may call our dedicated MVD Cell Repair Hotline to get connected with an expert. No one, anywhere is better at drives than EMA.