Boosting Chiller Performance with Variable Frequency Drives

Commercial and industrial chiller systems are essential for a wide range of applications, from ensuring comfortable building environments to supporting critical industrial processes.

Because maintaining consistent year-round temperatures in these environments is difficult, optimizing HVAC performance by integrating advanced motor technology, variable frequency drives (VFDs) and sine wave filters with chiller compressors is crucial.

In fact, it’s a necessity for maximizing performance and minimizing operating costs.

This article examines the advantages of integrating KEB’s high-speed VFDs and harmonic filters with chiller systems, exploring their features and demonstrating their impact on energy savings, performance, and reliability.

VFD-Controlled Chillers

At the heart of every chiller system lies a carefully orchestrated process, a closed-loop refrigeration cycle, driven by several key components.

The compressor raises the refrigerant’s pressure and temperature, initiating the cycle. The condenser then dissipates the heat, causing the refrigerant to condense. In the evaporator, the refrigerant absorbs heat from the chilled fluid, and the expansion valve regulates the refrigerant flow to maintain the cycle’s efficiency.

Traditional chillers often operate at full capacity even when cooling demand is low, resulting in significant energy waste. However, VFD-controlled chillers dynamically adjust the compressor speed to precisely match cooling output with actual demand.

This method helps eliminate overcooling and significantly improves energy efficiency, leading to lower operating costs.

Read more about 5 Things You Should Know about VFDs for High-Speed Compressors.

Migration to High-Speed Motor Technology

Variable frequency drives have long been integral to chiller technology, but the introduction of high-speed, permanent magnet (PM) motors marks a significant advancement in this field.

These motors can produce impressive power outputs by operating at extremely high speeds, often exceeding 50,000 RPM. This newer technology typically requires specialized solutions, such as magnetic or airfoil bearings and advanced liquid cooling systems.

PM motors offer additional advantages, including higher efficiency and a smaller footprint compared to traditional induction motors. This results in compact chiller designs and space savings. A big win for end-users.

 
Precise control of high-speed PM motors relies on VFDs that produce high frequencies, specifically 599 Hz and above, ensuring operation at the motor’s optimal efficiency points.

Regardless of the cooling method (air or liquid) or the type of compressor (scroll, screw, or centrifugal), high-speed VFDs and motors improve chiller performance across a wide range of applications, including food and beverage processing, plastics manufacturing, cryptocurrency mining, and more.

The Data Center Boom

The explosive growth of artificial intelligence is driving a surge in data center construction, from edge deployments to hyperscale cloud facilities. As of January 2025, there are over three thousand data center facilities in the United States, according to the USA Data Center map. In February 2026, that number has rocketed to nearly 4100 with Virginia, Texas, and California leading the way as key hubs.

Whether at the edge, in an enterprise setting, or a colocation facility, data centers share a critical challenge: maintaining a consistent temperature, typically between 65 and 75 degrees Fahrenheit.

Heat generated by internal components like power distribution units, servers, and storage devices, combined with external climate conditions (temperature, humidity, and altitude), requires precise temperature control to guarantee the reliable operation and long lifespan of sensitive equipment.

 
Data centers are energy hogs. In the International Energy Agency 2024 electricity report, the United States is home to 33 percent of the world’s data centers. Energy consumption in these centers is projected to rise from 200 terawatt-hours (TWh) in 2022 to 260 TWh by 2026, which will account for approximately six percent of the country’s total power usage.

Given this substantial energy demand, minimizing waste and optimizing efficiency are critical to the stability of the power grid infrastructure.

In the face of diverse cooling requirements, fluctuating energy costs, and varying environmental conditions, adaptability is key. KEB’s variable frequency drives, filters, and chokes provide the necessary flexibility and efficiency for modern chiller systems, offering a robust solution to the complexities of data center cooling and beyond.

Minimize Energy Consumption

How do VFDs improve the cooling efficiency of chillers? The quick answer is by precisely controlling the speed of the compressor motor.

Traditional chillers operate at a fixed frequency of either 50 or 60 Hz (full speed), regardless of the cooling demand. In contrast, VFDs dynamically adjust the frequency supplied to the motor, allowing for direct control over its speed and the compressor output. This capability enables the chiller to match its cooling capacity to the actual demand.

During periods of low cooling demand, a VFD reduces the compressor speed, leading to substantial energy savings. The energy reduction is roughly proportional to the decrease in speed, meaning the chiller consumes less power when cooling needs are lower. This feature is particularly beneficial during off-peak hours or in applications with fluctuating cooling loads.

Additionally, since chillers often run under part-load conditions, VFDs optimize compressor speed, leading to enhanced part-load efficiency, a crucial element in reducing overall energy consumption.

Lastly, VFDs enable “soft starts” by gradually increasing motor speed, which helps reduce the large current surges typical of traditional motor starts. This approach lowers inrush current, minimizes stress on the electrical system, and contributes to further energy savings.

Key VFD Attributes for Chillers

Not all drives on the market are equal. Selecting the right drive for new builds or retrofits requires careful consideration of several key factors.

Climatic conditions, for example, often dictate the drive type. Liquid-cooled drives excel in harsh environments with high temperatures, humidity, or dust, offering superior heat dissipation and reliable operation compared to air-cooled alternatives.

 
Motor compatibility is equally important. Chillers utilize diverse motor technologies, from the common induction motor to the highly efficient permanent magnet motor. A versatile VFD should support all these motor types to ensure maximum flexibility.

VFDs should integrate seamlessly with chiller control and Building Management Systems (BMS). This requires support for common communication protocols like EtherCAT, Ethernet/IP, Modbus, or Profinet.

Ensure the VFD includes harmonic filtering capabilities, either integrated or external, to minimize harmonic currents and preserve power quality.

KEB Solutions for Chillers

For high-speed chiller applications, KEB simplifies procurement and integration by offering a complete range of drive solutions, including VFDs, harmonic filters, and sine wave filters, all from a single source.

F6 VFDS

KEB’s F6 drives deliver exceptional performance, offering outputs of up to 450 kW and 800 A, with high switching frequencies reaching up to 16 kHz and output frequencies as high as 2000 Hz.

 
For reliable operation in corrosive environments, these air- or liquid-cooled VFDs (up to 55°C liquid) feature 3C3 coating for circuit-level protection.

They offer encoderless speed control for a wide range of motor types, including IPM, PM, asynchronous, and synchronous reluctance, and are suitable for both indoor and controlled outdoor installations.

A multi-Ethernet interface ensures flexible connectivity, while integrated encoderless safety functions provide reliable speed monitoring. This level of customization empowers machine builders to tailor drive solutions that align with their specific chiller requirements.

VFD Software

Combivis 6, KEB’s VFD software tool, reduces engineering time with its robust features, including a 16-channel scope for detailed trace analysis and intuitive start-up wizards.

It also simplifies the configuration and analysis of real-time fieldbus communication. Direct access to all manuals and technical documentation for the entire KEB product portfolio is readily available within the software.

Furthermore, KEB’s proprietary sensorless closed-loop motor control technology enables precise speed and torque control of permanent magnet motors, even at high speeds, without the need for feedback devices. This simplifies installation and lowers overall system costs.

Sine Wave Filters

When paired with the F6 drive at higher frequencies, KEB’s sine wave filters mitigate overheating, reduce EMC emissions, and enhance the longevity of turbo blowers and radial compressors.

 
The KEB sine wave filters, with power ratings from 0.75 kW to 450 kW, enhance the efficiency and lifespan of high-speed motors. These filters effectively tackle common challenges associated with high-speed motor operation, particularly the overheating caused by current ripple due to the motor’s low main inductance.

KEB’s sine wave filters effectively reduce rotor temperatures by over 80%, mitigating critical issues such as bearing wear, eddy currents, current ripple, and iron losses.

 
This substantial temperature reduction results in improved motor efficiency and extended lifespan while also enabling the use of extended motor cable lengths exceeding 100 meters without performance degradation.

Furthermore, the modular design of KEB sine wave filters, which includes a motor choke, capacitor bank, and connection cable, allows for adaptable and flexible installation within the switch cabinet.

Harmonic Filters

When paired with the F6 drive, KEB’s harmonic filters are essential for maximizing chiller performance and reliability. They reduce harmful harmonic distortion, resulting in cleaner power and improved power quality.

 
Additionally, harmonic filters protect components like capacitors and transformers from premature failure, extending system longevity.

This optimization leads to better temperature control, lower energy consumption, and potentially reduced noise and vibration.

Choosing a Drive Partner to Help with Development

Collaborating with experts across disciplines is crucial for developing high-speed turbo blowers. This often involves impeller design, bearings, motors, and drives specialists.

With over 200,000 high-speed installations globally, KEB is a leading provider of high-speed drive technology for compressors and blowers. Engaging with us early in the design process offers significant advantages.

We can help OEMs navigate the complex tradeoffs between motor and drive selection. For instance, we can clarify the system-wide impact of design choices such as motor pole pairs, induction versus permanent magnet motors, and cooling methods (air or liquid).

This early understanding empowers OEMs to design a product that effectively achieves their target performance goals.

Furthermore, our ability to accurately simulate motor response under various conditions saves valuable time and engineering resources.

Our hardware-in-the-loop (HIL) simulation program offers exceptional accuracy (99.9%) by using actual control card hardware and known motor, sine-wave filter, and inverter data.

 
This virtual commissioning approach significantly reduces the need for physical testing while providing critical insights for optimizing motor, drive, and filter selections to meet performance targets.

Customer Success

KEB has a long history of providing reliable and efficient high-speed drive solutions. Here are a few real-world examples demonstrating our ability to deliver reliable and cost-effective solutions for diverse blower and compressor applications.

Neuros

A South Korean manufacturer of turbomachinery utilizes KEB’s drive solutions in its high-performance turbo blower applications, particularly within demanding environments like sewage treatment plants.

These turbo blowers require drive controllers engineered for challenging conditions, and KEB provides the specialized drives necessary to ensure reliable and efficient operation in these applications.

Video: See How It Works

Piller Blowers & Compressors

The manufacturer of blowers and compressors uses KEB’s drive technology to power its VapoFan blowers (steam compression with low mass flows) for Mechanical Vapor Recompression (MVR) applications.

This optimized drive system, combining a Piller synchronous motor with a KEB drive controller and sine-wave filter, minimizes energy loss and significantly reduces steam consumption in various industrial processes.

Case Study: Discover the Benefits

Gardner Denver

Gardner Denver’s Ultima U160 dry screw compressor, featuring KEB drives and filters, achieves 97% energy efficiency and a 37% smaller footprint than comparable industrial compressors, all while maintaining a quiet 63-69 dBA noise performance.

Video: Customer Testimonial

Contact KEB America

Looking to optimize performance, improve efficiency, and ensure reliable operation of your industrial chiller systems? KEB America offers a comprehensive range of high-speed drive solutions tailored to the specific demands of your chiller applications.

Contact our team to discuss your requirements and find out how our expertise can help you develop new designs or retrofits.