October 26, 2017 by Jonathan Mosterd
Building automation and advancements in efficiency have exponentially increased over the last few decades, bringing about a new era in industry. With this, a whole new series of electronic devices have been integrated in large commercial buildings and in industrial and residential environments. These devices help automate and improve system performance, all while reducing energy and improving user experiences. This new equipment calls for a change in mindset toward maintenance. Maintenance is no longer about just checking belts, greasing bearings and cleaning filters; rather, it must also reflect taking care of electrical equipment as well.
When looking more specifically at the maintenance of electrical motors, a more comprehensive view is required. This is because many pump and fan motors are now using variable frequency drives. They too have recommended maintenance guidelines that include regular inspections, replacement parts and predictive monitoring. It is important to not only install and start up these units correctly, but also to perform regular maintenance on them to protect your investment.
Information regarding maintenance work can be found in multiple places and as such the best thing to often do is seek out assistance. Almost all AC drive manufacturers have published guidelines and a recommended scope of work, which are typically found in user or installation manuals. Also, many manufacturers are training and developing factory-authorized service partners that can be hired to inspect equipment, or they offer training for end users. Knowing which option to select is best answered by knowing what work needs to be completed, which areas should be checked, and what items should be replaced at specific intervals in a typical VFD maintenance program.
A good preventive and predictive maintenance program will take a holistic approach to the VFD. It should begin with an assessment that catalogues things such as the environment, quantity of units and average operational time. From there, it will produce a plan of maintenance that will be unique to each item’s requirements. Drives in harsher environments will require work and parts regularly, while those that are more protected will not need as much. The assessment should also produce a plan that will consider things such as spare parts availability produce digitally backed up parameters and provide different levels of service options for customers to choose from. It should also address worst case scenarios, such as what happens if a VFD fails due to an unexpected event and how long could the process continue without it.
Whatever the interval of service, the main focus of any maintenance program is to remove dirt and debris. This is especially important for the main heatsink. It helps pull heat from the main power components in a VFD: the rectifiers, capacitors and IGBTs. These components are primarily rated on their ability to handle the heat generated by current flowing through them. If the heatsink becomes blocked or layered with oil, dust or other foreign objects, it will decrease its ability to dissipate heat and reduce the life expectancy. Yet, dirt and debris are not just limited to the external parts of the unit. In many drives, this contamination can also get inside and cause problems with circuit boards. It is important to remove debris from these as well, as the reduced ability to cool components inside the drive will cause premature failures. Further, if there is any chance conductive material is entering the VFD, there is a high probability that it will create short circuits that generate non-repairable damage.
Working with your manufacturer is key. They can communicate many of the best practices and tools used in the industry. For instance, when removing debris from inside the drive unit, anti-static and oil free tools are important. Using and antistatic vacuum will prevent someone from inducing a charge into a component that will cause it to fail, or create long-term damage. Further, pressurized air needs to be both oil and water free. This will help to prevent more problems from arising. It is important to be trained and to get the tools that are recommended. Depending on your circumstances and access to competent service people, the other option may be to seek out professionals who already have the maintenance tools and are doing the work on a regular basis.
When considering factory-trained professionals, there are other benefits to consider. First and foremost is that they get to know your equipment. In the event that there is a failure outside your control, you will already have contacts who can provide support. Many of these service groups have 24/7 technicians available as well as inventory. Further, a good preventive and predictive maintenance program will also provide you with a list of critical spares in the event the unexpected happens. They can assist in recommending spare parts to keep on hand based on their experiences with the product. In the event a component fails at an inconvenient time, everyone will know what is on the shelf, which ultimately improves the response time.
Trained professionals will also have access to new products and upgrades. They will be able to advise if there are new options available to meet your needs, or possibly new software that will improve efficiency. While doing the PM they may be able to utilize their experiences and industry knowledge to help reduce costs and increase performance, all while keeping your equipment running.
The last part of a good preventive maintenance program is lifecycle prediction. The end of life for equipment may be due to reliability concerns, or it may be the result of a lack of available parts. Finding the right economic balance between maintenance parts and a new unit may determine when it is time to upgrade. On the other hand, there is also a time when many of the components within a unit need to be replaced for reliability concerns. The labour to perform the work, coupled with the parts, may dictate that it is more economical to purchase a whole new unit.
As the industry continues to grow, many manufacturers have recognized this need and are starting to partner with end users to assist with these upgrades. Whether maintenance is performed locally or outsourced, there are a number of retrofit, or smart step, programs available to assist you. These help to plan upgrades over a long period of time, all while spreading costs over a number of years and budgets.
In the end, not every drive or electronic failure can be prevented. Items such as lightning, power imbalances and spikes, or even a misplaced forklift can cause the unexpected to occur. Partnering with the right people and investing in the right inventory and tools can help to reduce downtime and minimize breakdown costs. A great preventive maintenance program will partner with end users over the entire life of a unit. It will begin with the initial assessments and continue all the way to planning a retrofit or upgrade. Selecting the right drive manufacturer, or factory authorized service group, is key to keeping an efficient and reliable process going.
Jonathan Mosterd is Canadian service manager with Danfoss.