Growing technology enhancements are providing new opportunities for power conversion and variable speed motor control. With improving efficiencies across system architecture, technology is helping to economically move industries forward into an energy transformation. By using less energy to perform work throughout product lifecycles, new opportunities with strong returns on investment arise — and serve as a stepping stone for many companies seeking to meet carbon neutrality goals.
Whether you are using variable frequency drives (VFDs) to move air or water, or even as power conversion devices such as in energy storage, the less you need to invest throughout the life of a product, the more advantageous the technology becomes.
When selecting efficient products, the rated efficiency is a good starting point but does not account for the entire application (or “big picture”). Often these efficiency values are measured in a lab by running equipment at full load in ideal conditions. They do not reflect unique end user installations which may not have ideal power or a lab-type installation. Instead, total application efficiency can be increased when equipment runs based on demand, especially when it is not required to run at full speed. Efficiency values also need to encompass the lifecycle of your project.
For example, consider your typical across-the-line contactor, or on/off fan and motor. You can purchase models rated for high efficiency, but they will always run at full power and speed when started, and will only be able to move a constant, fixed amount of air. Adding a variable speed drive that has the capacity to intelligently work with building management systems provides the ability to vary the energy consumed. This will allow you to slow down the fan and motor — thereby moving only the air you need, as well as heat, cool, or exchange air based on demand rather than at full capacity. Most often, a quick calculation of energy savings, especially considering a 24/7/365 runtime, can justify the initial costs needed to invest in a VFD.
Pumping systems, for example, where often there are large motors running at fixed speeds, traditionally use inefficient mechanical systems such as bypasses or throttling valves to maintain flow and pressure. By breaking down a single large horsepower motor into a series of smaller variable speed drives and motors, you can network the pumps to come online as demand grows. Further, you can turn off pumps and motors when they are not required (also known as “sleep mode”). Today, this can all be achieved with simple communication interface between drives that automatically balances runtimes and doesn’t require a separate controller. With this newer, integrated approach, you can expect longer mechanical life spans of the products as well as more redundancy to meet demand in case of an unforeseen failure.
The addition of intelligent controls to VFDs further helps to increase system efficiency throughout product lifecycles, thanks to preventative maintenance functions for both the VFD and the motor. In fact, condition-based monitoring enables VFDs to monitor motor windings, integrate vibration sensors, and build a nominal load profile to assess system integrity. This is all accomplished within the VFD and removes the need for an additional monitoring device. Combined with VFD scheduled maintenance counters, these new options provide systems data to help schedule maintenance. Instead of reacting to failures, which mean lost time and expensive fees, this data can help predict problems in the early stages. In doing so, you can order parts, schedule a shutdown and then perform the proper maintenance when equipment is scheduled to be available, rather than in an unexpected shutdown
With new adaptations to existing VFD structures, UPS-style storage can now be integrated to help plants ride through poor power episodes that often create unexpected system stoppages. Adding in energy storage can help to avoid long restart times, or even keep systems online for a short amount of time while backup generators start. This can be done on the AC distribution side for entire systems or focused on key components via the DC bus of VFDs. Further, flexible solutions involving grid converters and DC/DC power conversion can also allow you to capture wasted re-generative energy or enable the addition of other energy recovery systems to offset metered usage.
Efficiency is more than just a value on a singular component. Rather, it encompasses the entire application. Looking to how system architecture can work together to reduce total power required or event capture for later use is a key way to continue to transform how we use it in our everyday lives.
