How motor controls impact everything from energy efficiency to costs
Modern motor control systems, such as variable-frequency drives (VFDs) and servo drives, bring new levels of efficiency, precision and adaptability, offering clear advantages over traditional motor starters in performance, cost savings and scalability.
Learning Objectives
- Recognize how modern motor controls improve energy efficiency.
- Identify the maintenance and longevity benefits of VFDs and servo drives.
- Evaluate the adaptability and future-readiness of advanced motor control systems.
Motor control insights
- Modern motor control technologies foster energy efficiency for manufacturers.
- Variable frequency drives and servo drives help reduce maintenance efforts, particularly for equipment that requires frequent start and stop cycles.
- VFDs and servo drives not only offer energy efficiency, they also provider greater precision.
Motor control is foundational in modern technology and automation, directly influencing energy efficiency, precision and adaptability. Motion control technology has evolved greatly, bringing about systems far beyond traditional contactor-plus-overload setups.
While traditional motor starters remain a low-cost, straightforward option, they lack the capability to address key operational costs and long-term performance needs. These shortcomings open space for modern solutions like variable frequency drives (VFDs) and servo drives, which deliver clear advantages, including enhanced energy efficiency, greater precision and the flexibility to adapt to future needs.
VFDs are particularly efficient, adjusting motor speed to meet workload demands and significantly reducing electricity consumption and operational costs. Servo drives elevate this efficiency by using regenerative braking to capture energy during braking cycles and returning it to the power network, further improving energy usage.
Beyond energy savings, these advanced systems provide a high degree of precision, allowing for accurate speed and positioning adjustments crucial for applications in robotics, computer numerically controlled (CNC) machining and coordinated motion systems. Unlike traditional motor starters that simply cut power and allow motors to coast to a stop, VFDs and servo drives actively control deceleration, enhancing line performance and allowing synchronized operation across multiple systems.
As industries evolve to meet new demands in production, quality and safety, advanced drives also support a wide array of communication protocols, facilitating seamless integration into more complex control environments. Some essential aspects of motor control include energy efficiency, maintenance, scalability and precision.

Figure 1: Highlighting the complexities of a two-speed reversing motor control setup. Courtesy: Concept Systems Inc.
How modern motor control promotes energy efficiency
One of the most significant differences between traditional motor starters and modern drives lies in energy efficiency. Motor starters, once engaged, supply all available energy to the motor, regardless of workload requirements. This leads to wasted electricity and unnecessary costs.
VFDs, though initially two to three times more expensive than motor starters, adjust energy consumption based on workload needs. This means the motor uses only the energy required, saving electricity and lowering operating costs.
Servo drives with regenerative braking capability take this a step further by capturing energy produced during motor braking and returning it to the power network, further reducing energy consumption and dependence on the power grid.
How VFDs and servo drives improve maintenance efforts
Motor starters, while simple to maintain with easily replaceable components, are prone to wear. This wear is particularly pronounced in systems with frequent motor start-stop cycles.
VFDs and servo drives use solid-state circuitry, which experiences far less wear from electrical switching. These systems also have built-in monitoring tools that provide insights into motor and drive health through trends in current consumption, making it easier to predict failures and plan for maintenance down time.

Figure 2: Variable frequency drives reduce wiring within control panels. Courtesy: Concept Systems Inc.
Future-proofing machinery with modern motor control solutions
The constant evolution of industrial machinery means that systems often require upgrades to meet new production demands, quality improvements or evolving regulatory requirements. While traditional motor starters may still function, they often lack the flexibility needed to accommodate these changes. VFDs and servo drives, on the other hand, offer built-in scalability and adaptability, making future growth more manageable and cost-effective.
For instance, a VFD can be slightly larger than the current motor, allowing for an easy motor upgrade to handle increased torque or horsepower without replacing the drive. This facilitates higher performance when needed and extends the longevity of the hardware by running below maximum capacity.
Furthermore, VFDs and servo drives support both traditional hardwired control systems and more advanced communication protocols like Ethernet, Profinet or Modbus. This dual functionality allows for an easy transition from basic motor control to sophisticated automation without requiring additional hardware. Initially, the drive can operate using the existing control setup, but when higher-level control is required, it can seamlessly integrate into a more complex system via communication protocols.
Finally, safety is another area where modern drives shine. As safety regulations become more stringent over time and as machinery operates at higher speeds and with more potential hazards, systems must be designed to meet these requirements. Many VFDs and servo drives come with integrated safety features such as safe torque off or safe limited speed, which can be incorporated into emergency shutdown systems with minimal additional wiring.
In contrast, traditional motor starter setups often require the installation of separate safety contactors or relays to meet updated safety standards. Investing in drives with built-in safety functions not only ensures compliance with current regulations but also prepares the system for future safety requirements.

Figure 3: Modern servo drives with Ethernet communication enhance precision. Courtesy: Concept Systems Inc.
How to enhance precision with VFDs and servo drives
Beyond the ability to vary motor speed, one standout benefit of VFDs and servo drives is the inherent enhanced precision in motor operation. VFDs and servo drives allow for highly accurate positioning and torque control, making them ideal for applications where precision is critical, such as in robotics, CNC machines and other coordinate motion systems.
In motor starter applications, the removal of electrical power at the motor creates a coast to stop scenario. This coasting makes it difficult to pinpoint where to place sensing devices to account for the delay in stopping. While external sensing devices are still required, VFDs can actively ramp down or dynamically stop instead of coasting. Servo drives with their closed-loop sensing via motor encoders can actively stop at a motor angle instead of physical position in space. This enhanced precision creates a smoother running line and allows a for multiple systems to better synchronize to each other.
The disadvantages of VFDs and servo drives
While there are many advantages to using VFDs and servo drives, they are not without challenges.
- Power quality: VFDs and servo drives can create power quality issues due to their sensitive and high-frequency power circuits. Protecting the system may require additional equipment like line reactors or filters to safeguard both the drive and the power supply from interference.
- Motor wiring: The high frequency switching of VFD and servo drive output can create noise on nearby wiring and devices. Higher cost special cabling that is shielded needs to be used for connecting to motors. Additionally, motors must be rated for the high-frequency switching power provided by VFDs to avoid damage.
Big-picture considerations for VFDs and servo drives
Evaluating motor control systems requires looking beyond initial costs to consider long-term efficiency, adaptability and overall system reliability. While traditional motor starters may appear attractive due to their low cost, they lack the versatility and precision of modern solutions like VFDs and servo drives. These advanced drives deliver enhanced performance, reduced maintenance and built-in scalability, giving them an edge in energy savings, precise control and future-proofing.
Selecting the right motor control system from the outset is a strategic choice that can yield considerable savings in time, money and resources over the equipment’s lifespan.
Michael Blass is the design manager for Concept Systems Inc. Edited by Sheri Kasprzak, managing editor of automation and controls, WTWH Media, skasprzak@wtwhmedia.com.
Do you have experience and expertise with the topics mentioned in this content? You should consider contributing to our WTWH Media editorial team and getting the recognition you and your company deserve. Click here to start this process.