What is the Difference Between VFD and Servo Drives?

Servo vs VFD: Choosing the Right Drive for Your Needs

Servo systems are renowned for their precision in CNC machining, robotics, and factory automation. A key component within a servo system is the servo drive, which controls the electric servomotor. While servo drives excel in performance, VFDs (Variable-Frequency Drives) offer a compelling alternative, particularly for their energy-saving potential. Since both are widely used in industry, understanding their key differences is crucial for selecting the right option for your application

Understanding Servo Drives and VFDs

Focus and Applications

The VFD is a type of motor controller that works in conjunction with an electric motor by varying the variables such as voltage and frequency supplied to the electric motora VFD directly controls the voltage and frequency supplied to the motor. VFDs are also known by other names such as AC drive, adjustable-frequency drive, inverter, and microdrive.

A servo drive is an integral part of a servo system that consists of a motor, a controller, a feedback device, and of course – a servo drive. Simply put, a servo drive is a part of the servo system that receives a particular command from a control system, amplifies it, and transmits the current to a servo motor in the system. The servo motor produces a motion, tailored to the command it has received. The command signal usually represents some of the physical variables such as torque, velocity, and the desired position.

• VFDs: Masters of Speed: Variable frequency drives excel at controlling the speed of AC induction motors. They adjust the motor’s power supply frequency and voltage, offering good speed regulation for applications like pumps, fans, and conveyors. While cost-effective, VFDs may not provide the same level of precision as servo drives.
• Servo Drives: Precision in Motion: Servo drives are champions of precise motion control. They utilize feedback mechanisms and advanced algorithms to control position, velocity, and sometimes torque of servo motors with high accuracy. This makes them ideal for demanding applications like robotics, CNC machining, and precision positioning systems, where superior speed, accuracy, and responsiveness are crucial.

Control and Feedback

• VFDs: Open or Simple Loop: Variable frequency drives can operate in open-loop or closed-loop control modes. However, they often lack sophisticated feedback mechanisms and rely on simpler speed control algorithms.
• Servo Drives: Closed-Loop Champions: Servo drives leverage advanced feedback mechanisms like encoders or resolvers for continuous monitoring of the motor’s position, velocity, and sometimes torque. This enables them to achieve precise closed-loop control of motion.

Speed and Torque

• VFDs: Wide Range, Basic Control: Variable frequency drives typically offer a broader speed range, allowing control of motors across a wide spectrum, from very slow to high speeds. However, their torque control is basic, adjusting through voltage and frequency variations.
• Servo Drives: Focused Range, Precise Control: Optimized for high-performance, servo drives may have a narrower speed range but offer precise control within that range, including very low speeds and high accelerations. They also excel in precise torque control at various speeds and loads, making them ideal for applications requiring accurate force control, like robotic arms and linear actuators.

Cost Considerations

• VFDs: Budget-Friendly Choice: For applications where precise motion control isn’t critical or cost is a major factor, VFDs are the more cost-effective option.
• Servo Drives: Investment in Performance: Servo drives, with their advanced control capabilities and superior performance, tend to be more expensive. However, for applications demanding high precision and performance, the increased cost is often a worthwhile investment.

Choosing the Right Drive

There’s no single “better” option between servo drives and VFDs. The ideal choice depends on your specific needs:

• For precise motion control: Servo drives are the clear winner. They excel at maintaining position, handling complex paths, and varying speeds and loads with high accuracy.
• For energy efficiency and basic speed control: VFDs are the way to go. They offer significant energy savings, extended motor life, and built-in protections against voltage fluctuations.

Here’s a quick comparison to help you decide:

Feature	Servo Drive	VFD
Control Focus	Precise positioning, velocity, torque	Primarily speed control
Feedback Mechanism	Closed-loop with encoder	Open-loop or simple closed-loop
Motor Compatibility	Permanent magnet motors	Squirrel-cage induction motors
Performance	Superior speed, accuracy, responsiveness	Good speed regulation
Energy Efficiency	Moderate	Excellent
Cost	More expensive	More cost-effective

And if you’re still confused about what direction to take, VFD or servo contact us today and we’ll set you straight!!

Integrated Portfolio Solutions

Maximize Performance with Allen-Bradley® PowerFlex® Drives

The PowerFlex® family of AC and DC drives delivers solutions that directly impact your bottom line. We offer a versatile range of control options, from basic speed regulation to advanced torque and speed control. This flexibility, combined with industry-standard motor control, empowers you to optimize any application and achieve peak productivity.

Here’s what sets PowerFlex® apart:

• Wide Range of Control Technologies: We offer a variety of control options to perfectly match your application’s needs.
• Enhanced Application Flexibility: Unique control features within the PowerFlex® family allow you to tailor performance for your specific needs.

By choosing PowerFlex® drives, you gain the tools to optimize your operation and achieve lasting success.

PowerFlex 4M is the most cost-effective of the PowerFlex family of drives and features feed-through wiring and Zero-Stacking (TM) for ambient temperatures

PowerFlex 400 is ideal for pump and fan applications. Built-in features such as purge and damper input provide a cost-effective solution for speed control in a broad range of variable torque fan and pump applications.

PowerFlex 520-series combines powerful performance with flexible control and focuses on ease of use. Each of the three drives in this family offers a unique set of features to distinctively match the needs of your application.

PowerFlex 755 AC drives include multiple control, hardware, and safety options. Built-in EtherNet/IP delivers real time operating data and easily integrates into the Logix control system. Ideal for applications requiring position, speed, or torque control up to 1500 kW/2000 Hp. DC input options available.

PowerFlex 753 AC drives feature standard built-in I/O plus three options slots for communications, safety, and additional I/O.

PowerFlex 755TS Drive –incorporates TotalFORCE technology into a traditional six-pulse drive. TotalFORCE can now be used in a wider range of applications including fan, pump, and conveyor applications to more advanced motor control processes that require high performance features typically found in specialized drive solutions. PowerFlex 755TS offers real-time operational intelligence, automated commissioning, and optimization.

PowerFlex 755TL Drive Provides harmonic mitigation and power factor correction by using active front end technology. By reducing the adverse effects of harmonic distortion, the drive helps to improve energy efficiency, reduce energy costs and minimize power distribution issues on the factory floor.

PowerFlex 755TR Drive- Features built-in regeneration capability that helps decrease energy consumption by delivering regenerative energy from motors back to the incoming supply. Line regeneration reduces the need for braking resistors and associated cooling equipment and helps avoid wasteful dissipation of energy. This drive also offers harmonic mitigation.

PowerFlex 755TM Drive System -Select from a series of predesigned configurations for regenerative, and non-regenerative common bus supplies and common bus inverters to optimize your system design and power consumption. A common bus drive system offers advantages such as design flexibility, energy optimization and reduced installation costs. PowerFlex 755TM systems provide harmonic mitigation and built-in regeneration capability.

PowerFlex 755T Drives Configured to Order – Our configured to order drives are factory delivered for PowerFlex 755TL, TR, and TM drives in frames 7…10. Packaging options include NEMA Type 1 and 12 enclosures. Options include: input circuit breaker and/or fuses, door-mounted push buttons and selector switches, optional doormounted HIM, and output contactor and/or sine wave (DV/DT) filter.

Armor PowerFlexVFD – you need for On-Machine in One Drive

• Integral Ethernet switch, safety, & security
• Easy configuration using Studio 5000 AOP
• Lower your design and installation costs
• VFD control is based on the PF525
• Improve OEE with ADC & predictive functions

PowerFlex® 6000T – Common control architecture across low voltage and medium voltage drives

Common control hardware architecture, firmware, and network interface software with PowerFlex TotalFORCE® drives like PowerFlex 755T

• Reduce integration, operation, and support costs
• Optimized performance with flexible motor control modes for Induction Motors• Streamlined design and commissioning experience
• Device health optimization with predictive and built-in maintenance alerts, maximizing availability

Kinetix Integrated Motion: Streamlined Machine Control

Kinetix Integrated Motion simplifies machine design, operation, and maintenance. This Rockwell Automation® offering seamlessly integrates with the Integrated Architecture system, allowing all components to be programmed and managed within the familiar RSLogix 5000® software and Studio 5000 Logix Designer application.

Two Powerful Network Options:

• EtherNet/IP: Leverages industry-standard Ethernet technology for cost-effective real-time control. This network uses CIP protocols for motion control, safety, security, and synchronization, ensuring seamless communication and interoperability across devices. Precise time synchronization further enhances performance for demanding applications.
• Sercos: Offers a high-speed, reliable connection using noise-resistant fiber-optic cables. This single cable replaces complex wiring, reducing installation time and costs. Advanced diagnostics are also available through the Sercos interface.

Benefits of Kinetix Integrated Motion:

• Seamless Integration: Combines Allen-Bradley controllers, high-performance networks, AC/servo drives, motors, and linear actuators for a unified system.
• Simplified Programming and Management: Utilizes a familiar software environment for efficient motion control programming, configuration, commissioning, diagnostics, and maintenance.
• Fast Commissioning: Catalog number driven configuration streamlines the process, while a comprehensive library of motion instructions caters to diverse application needs.

Overall, Kinetix Integrated Motion empowers you to build high-performing machines with minimal complexity

Kinetix 5100 servo drives provide a scalable, cost-effective servo control choice in a single product line. Kinetix 5100 drives support applications with standalone Micro800™ and Logix controllers for a range of performance requirements. With Integrated Architecture capabilities in mind – Kinetix 5100 drives can be readily integrated with specially designed Add-On Instructions in applications for Logix 5000 controller users. Designed for versatility, the Kinetix 5100 drives let you select the power you need and the ability to apply that power to fit the unique needs of your application.

Kinetix 5300 servo drives support integrated motion on the EtherNet/IP™ network. By using the Studio 5000 Logix Designer® application and Logix 5000™ controllers with motion EtherNet/IP capability, this cost-effective motion solution delivers high performance and scalability with Kinetix TLP servo motors that are matched to drive ratings for optimized system sizing. In addition, Kinetix 5300 drives also accept high-resolution and incremental feedback types that are required for many of the other Allen-Bradley® rotary and linear products.

The Kinetix 5500 servo drives and Kinetix VP servo motors provide a cost-effective motion solution that delivers high performance and scalability with motor windings matched to

drive ratings for optimized system sizing.

Enhancing the current midrange architecture portfolio, this motion system is designed to connect and operate with ControlLogix 5570 and 5580 controllers or CompactLogix 5370 and 5380 controllers by using the Studio 5000 environment and supporting the Integrated Motion on the EtherNet/IP network.

The Kinetix 5700 drive family helps expand the value of Integrated Motion and Integrated Safety on the EtherNet/IP network to large custom machine-builder applications. The power range of Kinetix 5700 drives is designed for machines with high axis-counts and high-power requirements.

Single and dual-axis inverters are available with integrated and hardwired safe torque-off (STO) and Safe Stop 1 (SS1) safety functions. Single-axis and dual-axis inverters – Accepts Hiperface DSL encoder feedback from Kinetix VP motor family – Accepts Hiperface and incremental encoder feedback from Allen-Bradley motors and actuators

• Induction motor frequency control, closed-loop control, and adaptive tuning
• Integrated motion and integrated safety on the EtherNet/IP network
• CIP Security communication across the EtherNet/IP network

THE INDUSTRIES AND APPLICATIONS WE SERVE

	Oil & Gas Oil pipeline pumps Natural gas pipeline compressors Induced draft fans Axial-vane compressors Reciprocating compressors Centrifugal compressors Electro Submersible Pumps, <10km Power Generation Feed water pumps Induced draft fans Forced draft fans Baghouse fans Water / Wastewater Raw sewage pumps Effluent pumps Low service/raw water pumps High service/finished water pumps Booster pumps Flood control pumps RAS pumps WAS pumps Aeration blowers Commercial HVAC/OEM chillers/compressors
			Mining & Steel (Metals) Slurry pumps Ventilation fans Descaling pumps Baghouse fans Cyclone feed pumps Tailings pumps Screw pumps Non-regen conveyors Forest Products Fan pumps Induced draft fans Boiler feed water pumps Line shafts Slurry pumps Cement Kiln induced draft fans Forced draft fans Cooler baghouse fans Raw mill induced draft fans Kiln gas fans Cooler exhaust fans Baghouse fans Material conveyors, non-regen Other Test stands Agitators

Servo Dynamics is an Authorized Distributor of Rockwell Automation – Allen Bradley VFDs and Servo Drives

Get Powerful Performance with Rockwell Automation VFDs and Servo Drives from Servo Dynamics

Servo Dynamics is proud to be an authorized distributor of Rockwell Automation in Vietnam, offering their industry-leading Variable Frequency Drives (VFDs) and Servo Drives. These high-performance drives provide precise motor control for a wide range of industrial applications, ensuring optimal efficiency and productivity for your operations.

Benefits of Rockwell Automation Drives from Servo Dynamics:

• Enhanced control and accuracy: Rockwell Automation drives deliver superior motor control, improving process precision and repeatability.
• Increased efficiency: Optimize energy consumption and reduce operating costs with advanced drive features.
• Reliable performance: Backed by Rockwell Automation’s reputation for quality and durability, these drives ensure long-lasting operation.
• Expert support: Servo Dynamics’ team of technical specialists have the knowledge and experience to assist you in selecting the right drive for your application and provide comprehensive support throughout the entire process.

Contact Servo Dynamics today to learn more about how Rockwell Automation VFDs and Servo Drives can help you achieve your automation goals.

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