The Complete Servo Motor Guide

What is a Servo Motor?

A servo motor is a rotational or translational motor that receives power from a servo amplifier and creates torque or force for a mechanical system, such as an actuator or brake.

Servo motors enable precise control over angular position, acceleration, and velocity. They operate within a closed-loop control system that continuously assesses the motor's output and adjusts it to achieve the desired conditions. This control mechanism employs positive feedback to manage the motion and final position of the servo shaft.

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Figure 1- Industrial Servo Motor

These motors can be constructed for both alternating current (AC) and direct current (DC). AC servo motors are predominantly utilized in heavy industrial machines due to their ability to withstand higher current surges. Conversely, DC servo motors are ideal for smaller applications with excellent control and feedback capabilities. The motor's speed is determined by the applied voltage frequency and the number of magnetic poles.

Servo motors are versatile and find applications across various manufacturing environments. They power collaborative robotics, conveyor belts, automatic door openers, CNC turning, radar systems, tracking systems, and many automation systems. They require a relatively sophisticated controller. The fundamental operating principle of a servo motor resembles that of an electromagnetic motor, differing primarily in their structure and function. Standard servo motors typically use plastic gears, while high-power servo motors employ metal gears.

Servo Motor Construction

The following figure illustrates the construction of a standard servo motor.

Figure 2- Servo Motor Construction

A servo motor consists of two windings: the stator and rotor. The stator winding is located on the motor's stationary component and serves as the field winding, while the rotor winding is situated on the motor's rotating part, known as the armature winding. The motor features two bearings on both sides to facilitate the free movement of the shaft. An encoder acts as a sensor to determine the motor's rotational speed and measuring revolutions per minute.

Once reserved for specialized projects that demanded precise control of torque, speed, and position, servo motors have become more affordable and are increasingly seen as viable alternatives to traditional induction motors and hydraulic and pneumatic actuators.

Though hydraulic and pneumatic systems tend to be less expensive than servo motors, servos are gradually replacing them in numerous applications that require precision. In such instances, servo motors offer significant advantages, including the absence of oil leakage and soil contamination issues, along with simpler and more precise actuation than hydraulic systems.

Another characteristic of servo motors is their compact design, featuring a smaller diameter and a longer rotor compared to conventional motors.

The error signal is produced by comparing the feedback signal with the input command position (the intended motor position) to identify any discrepancies. This output from the error detector alone cannot initiate motor movement; thus, it feeds into a servo amplifier, which enhances the error signal’s voltage and power levels, enabling the motor shaft to rotate to the desired position.

Servo Motor Types

Servo motors are categorized into two main types based on the required power supply: AC (alternating current) and DC (direct current).

DC servo motors, typically brushed permanent magnet motors, are preferred for smaller applications due to their low cost, efficiency, and simplicity. On the other hand, AC servos are gaining traction in industrial settings since they support applications demanding higher power while providing precision control and reduced maintenance requirements.

Figure 3- Servo Motor Types

AC servo motors are classified into synchronous and induction types. There is also a third type suitable for smaller tasks known as stepper motors. Below is a table that outlines the power capabilities and the key advantages and disadvantages of each type of servo drive:

Table 1- Servo Motor Types’ Characteristics

Direct Current Servo Motor

A DC servo motor comprises a small direct current motor, a feedback potentiometer, a gearbox, and an electronic drive/control loop circuit. Similar to a conventional DC motor, its stator is a cylindrical framework with a magnet situated on the inner side.

Figure 4- DC Servo Motor

The rotor consists of a brush and a shaft. Attached to this outer casing is a commutator and a metal support frame that accommodates the rotor, and the armature winding wraps around the rotor's structure.

In a DC servo motor, the brush consists of an armature coil that supplies current to the commutator. An encoder situated at the back of the rotor detects the rotational speed. With torque being proportional to armature current, this design enables the construction of controllers using simpler circuitry.

Torque direction in this servo motor is dictated by the immediate polarity of the control voltage. DC servo motors can be divided into series motors, control shunt motors, series shunt motors, and permanent magnet shunt motors.

A DC reference voltage is set corresponding to the anticipated output in the RC servo motor type. This voltage, depending on the control circuit, can be presented to the voltage converter through a potentiometer, a PWM generator, or timers. Adjusting the potentiometer will produce a corresponding voltage applied to the error amplifier's input. In digital control systems, a microprocessor or microcontroller generates PWM pulses to yield more precise control signals.

A position sensor measures feedback signals related to the current load position. This feedback is commonly captured by a potentiometer that produces a voltage proportional to the absolute angle of the motor shaft linked through a gear mechanism. This feedback voltage subsequently feeds into the error amplifier.

The error amplifier, operating as a negative feedback amplifier, aims to minimize the difference between its input voltages. It compares the current motor position voltage (inferred from the potentiometer) with the desired voltage for the target motor position (obtained from the pulse width to the voltage converter), and outputs the difference as a positive or negative voltage.

This error voltage informs the motor armature, amplifying the armature’s energy proportional to the error. The motor remains in rotation until the error diminishes to zero. Conversely, a negative error triggers a reversal of armature voltage, spinning the armature in the opposite direction.

Due to its minimal armature inductive reactance, this motor exhibits quick and accurate response to command signals. They find utility in multiple devices and numerically controlled machinery, with their configurations classified into four types:

Series Servo Motor

Figure 5- Series Servo Motor

Series servo motors generate high starting torque at a high current. These motors display minimal speed regulation, allowing for turnaround by reversing field voltage polarity via a split series field winding.

Split Series Servo Motor

Figure 6- Split Series Servo Motor

A split series motor operates as a field-controlled motor powered individually by the motor armature and maintains a standard torque-speed curve, exhibiting high stall torque and a rapid torque decline as speed increases.

Shunt Control Motor

Figure 7- Shunt Control Servo Motor

Shunt control motors feature both field and armature windings: field windings reside on the stator, while armature windings are located on the rotor. The two are connected in parallel to the DC source in a DC shunt motor.

Permanent Magnet Shunt Motor

Figure 8- Permanent Magnet Shunt Motor

This motor utilizes a stable magnet to provide field excitation, exhibiting performance comparable to an armature-controlled permanent field motor.

Alternating Current Servo Motor

The squirrel cage induction motor is powered by an assembly of shortened wire loops on a rotating armature. The rotor undergoes electromagnetic induction to generate voltage. The principal distinction between induction servo motors and standard induction motors lies in the thinner conductor bars in the servo's cage rotor, resulting in lower motor resistance.

These motors are robust, versatile, and capable of delivering substantial power; however, they are more suited for larger applications due to subpar performance at lower power settings. The most prevalent type of servo motor in the industry is the synchronous AC servo motor, which comprises a stator and rotor. The stator features a cylindrical structure and core, with the induction coil wound around the stator core, connecting to a conductor wire that powers the motor.

As the rotor consists of a permanent magnet, the alternating current induction present in the rotor does not influence the servo motor's operation. AC servo motors are also referred to as brushless motors due to their intricate structure. A schematic diagram of an AC two-phase induction servo motor system is depicted below:

Figure 9- AC Servo Motor

The reference input is provided through a theta angle of a synchronous generator's rotor axis, which in turn receives constant voltage and frequency. The three stator terminals from the synchronous generator are connected to the transformer terminals of the control circuit, allowing the desired rotor position to be communicated to the control system.

Initially, the generator shaft and control transformer shaft position will differ, which we identify as an error. This error corresponds to the voltage across the control transformer, which is subsequently amplified before it reaches the servo motor's phase control. The servomotor rotor will then rotate in such a manner that any positional errors are corrected to achieve the targeted position. This fundamental principle governs the axis position regulation in AC servomotors.

Modern servo drives predominantly employ programmable logic controllers (PLCs) and microprocessors to generate variable frequency and voltage for motor operation. Control strategies utilize PWM and PID techniques. A typical block diagram of an AC servo motor system, which integrates programmable logic controllers, position controllers, and servo controllers, is illustrated below:

Figure 10- Typical Servo Motor Block Diagram

Alternating current servomotors come in various sizes and are classified based on their operational movements.

Positional Rotation Servos exhibit a 180-degree movement range concerning their zero axis, equipped with mechanical components (stop gears) for precise stopping capabilities.

As suggested by its name, a continuous rotation servo has no limit to its rotational range. In this case, the servo input directly corresponds to the output speed and direction, enabling unhindered rotation in both clockwise and counterclockwise motions.

Furthermore, a rack and pinion mechanism allows linear-type servos to control shaft rotation, converting rotational adjustments into linear motion.

Controlling Servo Motors with PWM

Pulse Width Modulation (PWM) is a control methodology that employs a square wave signal to produce a variable signal. The variations in pulse widths or the duration each pulse remains at high or low logic levels dictate the signal's resolution. Consequently, the servo motor's rotational direction and speed are derived from this control signal.

Because of the number of pulses delivered in each cycle, servos can be categorized into Analog and Digital varieties.

Figure 11- PWM Controlling

Analog servos rely on PWM power signals for operational commands to the servo; however, this can result in delayed reaction times when generating torque due to inertia.

Digital servos, conversely, incorporate advanced technology for high-frequency command transmission, famously delivering approximately six times more pulses than analog signals. This elevated frequency minimizes reaction time and enhances smoothness in motor operation.

Figure 12- Analog VS Digital PWM Control

Applications of Servo Motors

Compact and efficient, servo motors play a critical role in applications necessitating precise positional control. Driven by pulse width modulated signals, these motors are predominantly utilized in computers, robotics, toys, CD/DVD players, and various electronic devices. Their application spans sectors where repetitive and accurate tasks are essential.

While the examples cover a wide range, servo motors are employed in countless other scenarios, from toys to intricate computer systems. Their delicate and programmable nature makes them indispensable in numerous industries and manufacturing processes.

The following list highlights some of the key applications of Servo Motors:

• In robotics, servo motors facilitate movement, enabling the arm to achieve specific angles.
• Robotic cars leverage servo motors to maneuver wheels, generating sufficient torque for movement, starting, stopping, and speed regulation.
• Conveyor belts, which transport products through various tasks, are dynamically controlled by servo motors that initiate and stop at precise intervals, as seen in labeling, bottling, and packaging operations.
• In cameras, servo motors adjust the lens to improve focus in out-of-focus pictures.
• Automatic door openers in public spaces like supermarkets, hospitals, and theaters utilize servo motors for operation.
• In textile manufacturing, servo motors power looms, knitting machines, and spinning and weaving equipment.
• Solar tracking systems leverage servo motors to adjust the tilt of solar panels, ensuring they face the sun.
• Metal-forming and cutting machinery employ servo motors to provide accurate motion control.

Advantages Of Servo Motor

The advantages of servo motors include:

1. Highly efficient electromechanical energy converters.
2. Compact design that delivers more power relative to size than competitors.
3. High variability in torque and power output.
4. Capability to achieve high speeds with rapid acceleration and minimal sound emission.
5. Inherent rotational sensors (encoders) offer greater accuracy and facilitate a closed control loop.
6. Ability to provide high-speed rotations and substantial torque in a compact form.
7. Translation of rotary or linear motions into digital signals.
8. Wide usability across diverse applications.
9. Remarkable durability, long lifespan, and consistent performance despite overload and high temperatures.

Disadvantages Of Servo Motor

Key disadvantages associated with servo motors include:

1. Servo motors necessitate tuning to stabilize feedback loops.
2. Servo motors may exhibit unpredictability in the event of component failures, demanding safety circuits.
3. Complex controllers require electronic support and encoders.
4. Peak torque capacities are limited to a 1% duty cycle, with potential damage from prolonged overloads.
5. Gearboxes may be essential for delivering power at elevated speeds.
6. Higher overall system costs may arise, often exceeding the installation expenses for stepper motor setups.

What Is The Difference Between Induction and Servo Motor?

Induction motors operate as open-loop systems, while servo motors function as closed-loop systems. The significant inertia of induction motors contrasts with the low inertia characteristic of servo motors, which makes servo motors ideal for applications requiring immediate and accurate load positioning.

How to choose a Servo Drive vs. a VFD?

Servo Drives and Variable Frequency Drives (VFDs) serve the purpose of driving motors and controlling motion, leading to confusion over when to select one over the other.

VFDs are primarily utilized with induction motors in applications that necessitate velocity control, as their frequency variability directly affects motor speeds. Notably, VFD systems function as open-loop controls without feedback, meaning they do not adapt to changes such as stalls, resulting in less precision in velocity than servo systems. VFDs can be programmed to accelerate to a defined speed and maintain that speed over extended durations.

Figure 13- SINAMICS VFD, From Siemens Automation

As with many engineering decisions, the distinction is often nuanced, with examples of servo drives and VFDs blending operational capabilities arising from technological advancements and consumer demands for expanded functionalities. These developments frequently allow servo drives to power induction motors—both with and without feedback—and likewise, various VFDs can now operate with feedback mechanisms.

Generally, the decision becomes clearer based on the application's unique requirements, although there may be scenarios where both solutions are suitable.

For coordinated motion involving multiple axes, servo drives are unequivocally preferred. Likewise, any application demanding rapid acceleration or deceleration—such as pick-and-place systems—leads to the selection of servo drives. Additionally, precise sub-micrometer positioning typical in semiconductor industries benefits from servo technology.

VFDs, however, excel in conveying scenarios requiring fixed speeds or specific speed settings without complex navigation—such as conveyor belts and hydraulic pumps—or in instances like certain electric vehicles where high precision is unnecessary.

The overlap of capabilities becomes apparent in scenarios like velocity mode and position mode applications, where the precision expectations might lean towards a VFD's capabilities but align with a servo's broader features.

For example, a simple conveyor system may only require continuous operation at a single speed throughout the day, making a VFD a logical choice. However, more complex conveyor systems requiring dynamic adjustments—starting and stopping, changing direction, or synchronizing with other systems—would benefit from a servo setup.

Many conveyor systems present varying requirements, leading to overlaps in the capabilities of servo drives and VFDs. In the absence of a distinct choice, the decision-making process will generally focus on performance, features, and cost considerations.

Performance and Features

While assessing system options, consider the tradeoffs between the lower costs associated with VFD systems versus the superior performance and feature set of a servo drive system. Evaluate the specific motions the system needs to perform and developing features that enhance convenience.

Cost

Once you've identified potential candidates based on performance, consider cost implications. Servo systems typically come with higher price tags than VFD systems, mainly due to the cost contribution from servo motors. Unlike induction motors, which have lower manufacturing costs, servo motors with integral permanent magnets result in increased material expenses. Furthermore, because servo drives often incorporate more advanced features, their costs surpass those of VFDs. This necessitates a strategic evaluation of cost versus performance in making your choice.

Efficiency

In mobile applications reliant on battery power, efficiency takes precedence. Maximizing efficiency extends operational periods between charges, enhancing system uptime. Since servo motors use permanent magnets, they demonstrate higher efficiency than induction motors, positioning them favorably in this domain.

Size

Servo drives are typically more compact and integrated compared to VFDs. For smaller mobile applications, component size is critical, with smaller components facilitating system integration and reducing overall machine weight. The benefits of reduced weight translate into improved acceleration and longer battery life. Thus, when size constraints exist, servo drives offer a significant advantage over VFDs. Alternatively, VFDs remain a logical choice for high-power systems where AC induction motors can be constructed larger than servo motors.

Power

Power considerations become crucial for larger machines; while servo systems are limited to hundreds of kilowatts, induction systems can reach megawatt capacities. As power demands rise, servo systems eventually become inadequate compared to induction motors and VFDs, but this transition generally occurs at high power levels exceeding those typically found in most applications.

More Powerful and Compact

The finest characteristics of synchronous motors compared to their induction counterparts is their higher torque density. A servo motor of equivalent size to an induction motor typically generates 40-60% more torque. This means that a servo solution will inherently be smaller lighter than its induction counterparts, achieving required torque, speed, or power. Hence, a permanent magnet motor excels in applications with limited space or weight constraints.

For instance, servo motors shine in robotics applications that demand ply compact and lightweight designs offering high power, accuracy, and speed. The remarkable power output provided by servo motors—especially considering size and weight—significantly benefits robotics designers, leading to more compact, lightweight, and reliable solutions. This remains equally true for renewable energy scenarios such as wind energy, where efficient motor performance is paramount.

Low Inertia for High Dynamic Response

Being smaller in construction, servo motors exhibit lower inertia relative to comparable induction motors. Consequently, they can achieve accelerative performance and deceleration at greater speeds with precision. This enables enhanced accuracy in motion control applications, which are crucial in packaging machinery. Combined with EtherCAT Motion Controls, these low-inertia motors provide precise and synchronized movements suitable for various stages of the packaging line.

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Full Torque at Zero Speed

Another vital advantage of permanent magnet motors is their capacity to maintain full torque at zero speed indefinitely. This differentiates them from most induction motors, which struggle with limited low-speed torque and stability. Adjustments for VFD (e.g., Voltage Boost) can improve performance during low-speed operations but often result in heightened motor heating, inherently curtailing efficiency. When situations require holding torque at rest or low-speed operation placements, only a servo motor with corresponding feedback mechanisms suffices.

Higher IP Rated Protection

Beyond functional advantages in control, servo motors often come with enhanced protective designs. Most synchronous motors do not necessitate cooling fans, allowing them to achieve IP65 ratings, unlike traditional induction motors typically rated IP44 or IP54. Thus, servo motors tend to be more suitable for harsh environments, reducing risks of early equipment failure.

Figure 14- Servo Motor Design

With a brushless design, servo motors are particularly advantageous in environments requiring extensive durability. This includes sectors like food and beverage, where machine components must withstand large temperature variations and require frequent washdowns. Servo motors exhibit great benefits in various industrial applications subject to high temperature and pressure environments.

Increasingly Economical

Despite the considerable advantages of servo motors over induction motors, it may raise the question of why anyone would still select an induction motor. Historically, servo motors have been significantly pricier than their induction counterparts. Although they remain more expensive, the gap is narrowing.

Synchronous motors displaying comparable power specifications to induction motors are now available for only 10-20% higher costs. Previously, servo motors could be double the price of induction motors. This pricing divide is expected to continue decreasing as servo technology becomes more prevalent.

Servo Drive Manufacturers in Industrial Automation

Every variable interacted with in servo systems—such as torque, position, and velocity—forms part of an intricate motion control system that significantly impacts safety, efficiency, and equipment health. Thus, it’s crucial to utilize the correct components within servo systems to avert risks of overheating or early motor failures.

Globally, numerous OEM servo drive manufacturers produce various components, with some focusing on interchangeable designs, while others create drives tailored for specific applications. Here’s a look at ten leading servo drive manufacturers within the industrial automation space:

Allen Bradley

Figure 15- Allen Bradley Servo Hardware

Allen Bradley EtherNet IP Drives are offered in various models and can operate within any system supporting EtherNet IP. Their SERCOS Interface Models, suitable for both low and high-power applications, excel in compatibility with food-grade motors. Additionally, the Kinetix 300 and Kinetix 3 Single-Axis Component provide standalone, low-power flexibility for designers and builders.

Siemens

Figure 16- SINAMICS Drives Family

Siemens provides servo drives under the SINAMICS brand, addressing a variety of low to medium-voltage DC drive needs. Their standard models range from the V20, generating up to 30kW, to the G150/150, capable of producing high-level power. Additionally, models such as the G120 and G120C support mid-range capacities of 250 and 125 kW respectively.

Siemens also presents drives designed for specific industries, covering areas like conveyance and processing, including the G120X and G180 models that cater to complex systems requiring diverse communication methodologies for safety applications.

They offer energy-efficient S120 and S120CM drives for low-voltage projects, promoting notable scalability and modularity while prompting compatibility with various other elements. The high-performance modular S150 SINAMICS drive can recover energy for improved efficiency. The compact SINAMICS DCM drive responds effectively to straightforward, cost-effective high-performance needs.

Schneider Electric

Figure 17- Schneider Lexium Easy 26

Schneider's Lexium family is structured into distinct groups categorized by power and functionality. The segments include models such as Lexium 32, Lexium 23 Plus, and Lexium 28, offered in single and three-phase configurations. The Lexium 32 has a maximum power rating of 11kW, while Lexium 23 and Lexium 28 hold maximum ratings of 7.5kW and 4.5kW, respectively.

Schneider's PacDrive LMC controller family commands the standalone Lexium 52 drive, boasting high power density and self-sufficient configurations suited for individual-axis capabilities. Moreover, the multi-axis modular Lexium 62 can fit within half the cabinet space of comparable models, thus saving costs on mounting and cabling expenses. The 62 also supports PacDrive controllers and features inherent safety protocols through the SERCOS interface.

Omron

Figure 18- Omron Servo Drive Family

Omron servo drives encompass EtherCat, ML-II, and Analog/Pulse versions, all featuring built-in encoders as well as advanced tuning capabilities via disturbance, vibration, and anti-torque algorithms. Most models include functions like dynamic braking, load inertia detection, and over-travel protection.

Emerson/GE

Figure 19- PACMotion Servo Family

Emerson's PACMotion servo drives offer plug-and-play compatibility with servo motors, designed in a compact low-profile form. All units utilize EtherCat controllers while offering adaptability to third-party components. PACMotion servo drive options span across eight models, outputting from W to 16,000W, with four models featuring dual ratings at 120/240V AC and 240/480V AC. Up to 50 coordinated control axes can be incorporated into each system for larger operations, and all systems come standard with Safe Torque Off safety features.

ABB

Figure 20- ABB Servo Motors and Drives

ABB provides a broad selection of drive sizes and power ratings depending on application needs. Their low-voltage AC drives accommodate systems with capacities of up to HP, in addition to DC drives designed for heavy-duty industries like food, beverage, mining, and metal processing. ABB's DC drives exhibit the highest power-to-size ratios in the industry, with modular MicroDrives available for low-power requirements.

Mitsubishi Electric

Figure 21- MItsubishi Servo Motors and Drive

Mitsubishi's MELSERVO line offers fewer variations compared to others, yet all models utilize EtherNet-based optical communication to synchronize system components. Their product range includes the MR-J4-GF Family for compact applications, the MR-J4XX-B Family for tasks involving two or three axes, and the MR-J4-A Family designed for diverse general-purpose applications.

Servo Motor Troubleshooting

Every hardware or equipment piece may encounter problems over time; however, many common issues can be effectively managed with proper understanding. Several prevalent issues may arise regardless of maintenance, potentially culminating in motor failure during operation. Prior to disassembling a servo for component inspection, explore potential quick fixes. Here’s a brief overview of common servo motor issues and the corresponding solutions.

Overheating

Most servos are sensitive to heat, particularly during protracted operations. Though maintenance teams often report increased overheating instances in summer months, excessive overheating can occur at any time.

Overheating in servo motors can arise from various factors, including rising ambient temperatures, extended run times, inadequate ventilation, and even the age of the equipment. Older machines tend to overheat more easily as internal components wear out.

An overheating servo motor can damage equipment and jeopardize components connected to the system. Although many servo models incorporate failsafe mechanisms to shut down at dangerous temperature levels, such occurrences can still jeopardize equipment integrity and waste time for personnel.

To prevent overheating issues, ensure the work environment is climate-controlled, maintaining optimal temperature stability. You don’t need to keep the area excessively cold, but it's vital to avoid extreme temperatures.

Moreover, refrain from attempting to cool an operating servo by opening cabinets or using external fans, as this can introduce excess dust or debris and further strain the system. If working with older equipment, consider restoring it to boost efficiency and maintain working components.

Lastly, turn off any overheating system and allow it to cool before operating again. Continuing to operate frequently despite repeated overheating concerns may necessitate replacing the unit.

Servo Motor Won't Turn

Occasionally, you might observe that your motor fails to move. This situation can appear concerning, given the servo motor's intricate components; however, identifying the issue may be simpler than expected.

Check the output from the controller's Digital-Analog Converter. If it reads zero or near-zero, this indicates an issue with the controller, necessitating replacement. Should the output value be greater, the controller is functioning as intended.

In case the drive is suspected to be the source of the problem, executing a self-test can reveal whether the motor operates properly at low efficiency. If it remains non-responsive, the drive may require troubleshooting.

Servo Making Abnormal Noises

While some noise from servo motors is normal, excessive noise warrants concern. A typical operational noise is a modest hum; however, if the sound is excessively loud, it could suggest wiring issues or electrical problems. Ensure that the servo is correctly grounded and receiving proper power, and always power off the servo before working on its electrical components.

Servo Motor Producing Reduced Torque

Torque, representing the power or energy required to move a mechanism, arises from friction, external forces (such as gravity), and inertia alterations. Each motor exhibits a specific torque range by design, so an ill-suited motor may be unable to handle the required workload. Insufficient torque may also indicate a malfunctioning servo motor.

When diagnosing reduced torque, consider the following factors:

• The rating of the servo amplifier.
• The servo’s established workload limits.
• Low voltage or voltage drops in the system.
• Defective capacitors.
• Inadequate or improper wiring connections.

Servo Smells Bad or Produces Smoke

Any strong odor reminiscent of burning from the servo should prompt immediate attention. If you notice such odors or observe smoke, this is indicative of overheating.

Examine the cooling system or airflow to identify any obstructions. If accessible, ensure no dirt or debris has penetrated internal components. If preventive measures yield no results, verify that bearings maintain ideal functionality, as they may present complications like excessive lubrication or standard wear. A burning ozone smell signals potential winding or wiring fires, necessitating checks for proper wire contact and system grounding.

Servo Motor Stops Upon Reaching High-Speed Ranges

Diagnosing issues related to motor stalling during high-speed demands can be challenging due to the numerous contributing factors. Monitor the servo motor for irregular operational signs or physical malfunctions, such as rapid overheating, weakened bearings, faulty capacitors, velocity sensor problems, poorly maintained wiring, or excessive noise readings. Some subsystems might yield undesired results from overload protection, voltage fluctuations, inadequate motor specifications, or improper control designs.

Servo Motor Repair

In light of your preliminary analysis, reach out to the respective vendor or technical support regarding the drive. Once the problem has been established, you can proceed with repairs. Ensure all appropriate testing equipment and tools are on hand before initiating repairs, as fixing this technology often surpasses standard retail offerings.

Prior to activating the device, inspect the servo drive's electronics for damaged or burnt components, including MOSFETs, inputs, outputs, IGBT relays, feedback circuits, power supplies, and capacitors.

After turning on the machine, monitor the LED or readout display. If a screen is present but unresponsive, or if an alarm triggers before any lights activate, the servo drive is likely defective. If operations commence before an alert occurs, it can typically be excluded from the source of issues.

Assess both the servo drive and the motor for any damaged, missing, or mal-positioned components. Verify cable and motor plug conditions, replacing those exhibiting anomalies. Use diagnostic meters to evaluate whether the motor axis faces excessive friction.

While rare, friction can emerge from insufficient lubrication. Inspect the airflow systems or coolant in the motor housing for cleanliness, and check wiring for signs of obstruction. Look for binding in motor motion and assess the brushes of the DC motor. Validate incoming power sources using a voltmeter, ensuring the servo drive receives proper voltage.

As you navigate through the issue, pose the following questions:

• Are there any alarms, indicating slow feeding or rapid movement failures, or any sounds of humming? Potential issues may exist.
• If audible noises accompany rapid movements, consider the possibility of bearing damage.
• Does the motor halt abruptly, or does it gradually come to a standstill? This could suggest underlying electrical problems; ensure coolant remains clear from both the electrical box and motor axes.

Upon completing repairs or part substitutions, evaluate the servo motor before resuming regular duties. This can be achieved by plugging it into a universal tester that provides feedback concerning phases, rotation speeds, and directional movement under load. Avoid heavy workloads initially to confirm operational integrity prior to normal activities.

Servo Motor Hardware Overview

Industrial servo motor control systems comprise multiple devices responsible for actuating the servomotor in accordance with project specifications to meet process needs. Generally, the system is organized into the following device modules:

Figure 23- Siemens Controllers; S120 (left) and PLC S7- (right)

Control System: This system reads plant status and executes automation algorithms essential for servo operations, with PLCs and Control Units acting as operational cores.

Power System: Since industrial motors require diverse power specifications, power systems handle filtering, isolation, AC-DC conversions, and deliver the final power specifications directly to the motor. Components of this group include reactors, line filters, and motor modules.

Figure 24- SINAMICS Power System

Motor and Data Exchange: Once control algorithms have executed and power specifications have been transformed, this energy converts into physical actuation of the motor axis. Many advanced control systems do not strictly need servo motors, as numerous controllers support induction motors with encoders for the system's mechanical output. Nevertheless, suitable equipment (servo or induction motors) should be selected based on application specifics. Some industrial servo motors, such as those from Siemens automation, incorporate integrated data exchange protocols (DriveCliq) alongside their control systems, streamlining maintenance and operational needs.

Figure 25- Siemens Servo Motor and Drive

Commissioning a Sinamics Servo Drive from Siemens Automation

With ample knowledge about servo motors acquired, it’s time to witness the practical functionality by commissioning a Sinamics servo motor.

Sinamics Starter, Siemens Automation's leading software, enables configuration, parametrization, and control development for drivers and servo drivers. Proper commissioning is crucial to ensure secure operation across process control and machine tasks.

Conclusion

Servo motor systems widely support mechanical processes in industrial automation contexts. However, effectively specifying, installing, commissioning, programming, implementing, and maintaining these systems is complex. While multiple considerations affect these steps, expertise yields substantial rewards in terms of efficiency and accuracy across various automation tasks.

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