Servo motor principle
I. AC Servo Motor
The stator of an AC servo motor is basically similar in construction to that of a capacitor-split-phase single-phase asynchronous motor. Its stator has two windings positioned 90° apart: one is the excitation winding Rf, which is always connected to the AC voltage Uf; the other is the control winding L, connected to the control signal voltage Uc. Therefore, an AC servo motor is also called a dual-servo motor.
AC servo motors typically use squirrel-cage rotors. However, to achieve a wide speed range, linear mechanical characteristics, no "self-rotation," and rapid response, servo motors must possess high rotor resistance and low moment of inertia compared to ordinary motors. Currently, two common rotor structures are used: one is a squirrel-cage rotor with high-resistivity conductors made of high-resistivity conductive material; to reduce moment of inertia, the rotor is made slender. The other is a hollow cup-shaped rotor made of aluminum alloy with very thin walls (only 0.2-0.3 mm). To reduce magnetic reluctance, a fixed inner stator is placed inside the hollow cup-shaped rotor. The hollow cup-shaped rotor has very low moment of inertia, rapid response, and smooth operation, hence its widespread adoption.
When there is no control voltage, the stator of an AC servo motor only has a pulsating magnetic field generated by the excitation winding, and the rotor remains stationary. When a control voltage is applied, a rotating magnetic field is generated in the stator, and the rotor rotates in the direction of the rotating magnetic field. Under constant load, the motor speed varies with the magnitude of the control voltage. When the phase of the control voltage is opposite, the servo motor will reverse.
Although the working principle of an AC servo motor is similar to that of a split-phase single-phase asynchronous motor, the rotor resistance of the former is much larger than that of the latter. Therefore, compared with a single-phase asynchronous motor, a servo motor has three significant characteristics:
1. High starting torque
Due to its high rotor resistance, its torque characteristic curve, as shown in curve 1 of Figure 3, differs significantly from the torque characteristic curve 2 of a typical asynchronous motor. This allows for a critical slip S0 > 1, making the torque characteristic (mechanical characteristic) closer to linear and providing a larger starting torque. Therefore, the rotor rotates immediately upon the application of control voltage to the stator, exhibiting characteristics of rapid start-up and high sensitivity.
2. Wide operating range
3. No rotation phenomenon
A normally operating servo motor will immediately stop operating if the control voltage is lost. When the servo motor loses the control voltage, it operates in a single-phase state. Due to the high rotor resistance, the two torque characteristics (T1-S1 and T2-S2 curves) and the resultant torque characteristic (T-S curve) generated by the interaction of the two rotating magnetic fields rotating in opposite directions in the stator with the rotor are as follows.
The output power of AC servo motors is generally 0.1-100W. When the power supply frequency is 50Hz, the voltage is 36V, 110V, 220V, or 380V; when the power supply frequency is 400Hz, the voltage is 20V, 26V, 36V, or 115V, among others.
AC servo motors operate smoothly and with low noise. However, their control characteristics are nonlinear, and due to high rotor resistance, losses are high and efficiency is low. Therefore, compared with DC servo motors of the same capacity, they are larger and heavier, and are only suitable for low-power control systems of 0.5-100W.
What is the working principle of an AC servo motor?
The rotor inside a servo motor is a permanent magnet. The U/V/W three-phase electricity controlled by the driver creates an electromagnetic field, causing the rotor to rotate under the influence of this magnetic field. Simultaneously, the motor's built-in encoder feeds back signals to the driver. The driver compares the feedback value with the target value and adjusts the rotor's rotation angle accordingly. The accuracy of a servo motor depends on the accuracy (line count) of the encoder.
A servo motor is a motor that controls the operation of mechanical components in a servo system. It is a type of auxiliary motor with indirect speed change. Also known as an actuator motor, it is used as an actuating element in automatic control systems, converting received electrical signals into angular displacement or angular velocity output on the motor shaft. Servo motors are divided into two main categories: DC and AC. Their main characteristic is that they do not rotate when the signal voltage is zero, and their speed decreases uniformly as the torque increases.
Function: Servo motor , which enables very accurate control of speed and position.
DC servo motors are divided into brushed motors and brushless motors.
Brushed motors are low in cost, simple in structure, have high starting torque, wide speed range, and are easy to control. They require maintenance, but maintenance is convenient (replacing carbon brushes). They generate electromagnetic interference and have environmental requirements. Therefore, they can be used in cost-sensitive general industrial and civilian applications.
Brushless motors are small in size, lightweight, powerful, fast-responding, high-speed, low-inertia, smooth-rotating, and stable in torque. While their control is complex, they are easily made intelligent. Their electronic commutation is flexible, allowing for either square wave or sine wave commutation. The motors are maintenance-free, highly efficient, operate at low temperatures, have minimal electromagnetic radiation, and a long lifespan, making them suitable for various environments.
AC servo motors are also brushless motors, and they are divided into synchronous and asynchronous motors. Currently, synchronous motors are generally used in motion control because they have a wide power range and can achieve very high power. They have high inertia, low maximum rotational speed, and their speed decreases rapidly as power increases. Therefore, they are suitable for applications requiring low-speed, stable operation.
Explanation of basic knowledge about servo motors
Servo motor
A servo motor, also called an actuator motor or control motor, is an actuator in automatic control systems. Its function is to convert signals (control voltage or phase) into mechanical displacement, that is, to transform received electrical signals into a certain speed or angular displacement of the motor. Its capacity is generally between 0.1-100W, with 30W and below being commonly used. Servo motors are available in both DC and AC versions.
I. AC Servo Motor
The stator structure of an AC servo motor is basically similar to that of a capacitor-split-phase single-phase asynchronous motor, as shown in Figure 1. Its stator has two windings positioned 90° apart: one is the excitation winding Rf, which is always connected to the AC voltage Uf; the other is the control winding L, connected to the control signal voltage Uc. Therefore, an AC servo motor is also called a dual-servo motor.
AC servo motors typically use squirrel-cage rotors. However, to achieve a wide speed range, linear mechanical characteristics, no "self-rotation," and rapid response, servo motors must possess high rotor resistance and low moment of inertia compared to ordinary motors. Currently, two common rotor structures are used: one is a squirrel-cage rotor with high-resistivity conductors made of high-resistivity conductive material, where the rotor is made slender to reduce moment of inertia; the other is a hollow cup-shaped rotor made of aluminum alloy with very thin walls (only 0.2-0.3 mm). To reduce magnetic reluctance, a fixed inner stator is placed inside the hollow cup-shaped rotor, as shown in Figure 2. The hollow cup-shaped rotor has very low moment of inertia, rapid response, and smooth operation, hence its widespread adoption.
Figure 1 Schematic diagram of AC servo motor
Figure 2. Structure of the hollow cup-shaped rotor servo motor
When there is no control voltage, the stator of an AC servo motor only has a pulsating magnetic field generated by the excitation winding, and the rotor remains stationary. When a control voltage is applied, a rotating magnetic field is generated in the stator, and the rotor rotates in the direction of the rotating magnetic field. Under constant load, the motor speed varies with the magnitude of the control voltage. When the phase of the control voltage is opposite, the servo motor will reverse.
Although the working principle of an AC servo motor is similar to that of a split-phase single-phase asynchronous motor, the rotor resistance of the former is much larger than that of the latter. Therefore, compared with a single-phase asynchronous motor, a servo motor has three significant characteristics:
1. High starting torque
Due to its high rotor resistance, its torque characteristic curve, as shown in curve 1 of Figure 3, differs significantly from the torque characteristic curve 2 of a typical asynchronous motor. This allows for a critical slip S0 > 1, making the torque characteristic (mechanical characteristic) closer to linear and providing a larger starting torque. Therefore, the rotor rotates immediately upon the application of control voltage to the stator, exhibiting characteristics of rapid start-up and high sensitivity.
Figure 3 Torque characteristics of the servo motor
2. Wide operating range
As shown in Figure 3, the servo motor can operate stably within the range of 0 to 1 when the difference rate S is between 0 and 1.
3. No rotation phenomenon
A normally operating servo motor will immediately stop operating if the control voltage is lost. When the servo motor loses the control voltage, it operates in a single-phase state. Due to the high rotor resistance, the two torque characteristics (T1-S1 and T2-S2 curves) generated by the interaction of the two rotating magnetic fields rotating in opposite directions in the stator with the rotor, as well as the resultant torque characteristic (T-S curve), are shown in Figure 4. These characteristics differ from the torque characteristics of a typical single-phase asynchronous motor (T′-S curve in the figure). The resultant torque T in this situation is the braking torque, which causes the motor to stop quickly.
Figure 4. Torque characteristics of the servo motor during single-phase operation.
Figure 5 shows the mechanical characteristic curves of the servo motor during single-phase operation. With a constant load, the higher the control voltage Uc, the higher the speed; conversely, with a constant control voltage, an increase in load leads to a decrease in speed.
Figure 5 Mechanical characteristics of the servo motor
The output power of AC servo motors is generally 0.1-100W. When the power supply frequency is 50Hz, the voltage is 36V, 110V, 220V, or 380V; when the power supply frequency is 400Hz, the voltage is 20V, 26V, 36V, or 115V, among others.
AC servo motors operate smoothly and with low noise. However, their control characteristics are nonlinear, and due to high rotor resistance, losses are high and efficiency is low. Therefore, compared with DC servo motors of the same capacity, they are larger and heavier, and are only suitable for low-power control systems of 0.5-100W.
II. DC Servo Motor
The structure of a DC servo motor is the same as that of a regular DC motor, except that it is made longer and thinner to reduce rotational inertia. Its excitation winding and armature are powered by two independent power supplies. There are also permanent magnet types, where the magnetic poles are permanent magnets. Armature control is usually used, where the excitation voltage f is constant, the established magnetic flux Φ is also constant, and the control voltage Uc is applied to the armature. Its wiring diagram is shown in Figure 6.
Figure 6 Wiring diagram of DC servo motor
Figure 7 shows the mechanical characteristic curves of a DC servo motor under different control voltages (Uc is the rated control voltage). As can be seen from the figure: under a certain load torque, when the magnetic flux remains constant, increasing the armature voltage increases the motor speed; conversely, decreasing the armature voltage decreases the speed; when Uc = 0, the motor immediately stops. To reverse the motor, the polarity of the armature voltage can be changed.
Figure 7. Curve of n=f(T) for DC servo motor
Compared with AC servo motors, DC servo motors have advantages such as stiffer mechanical characteristics, higher output power, no self-rotation, and large starting torque.
The principle of AC servo motors
An AC servo motor has a stator with three-phase symmetrical windings, while the rotor has permanent magnetic poles. When three-phase power is applied to the stator windings, a rotating field is inevitably generated between the stator and rotor. The speed of this rotating magnetic field is called the synchronous speed. The motor speed is also the speed of the magnetic field. Because the rotor has magnetic poles, it can rotate even at extremely low frequencies. Therefore, it has a wider speed range than an asynchronous motor. Compared to a DC servo motor, it has no mechanical commutator, and especially no carbon brushes, completely eliminating the wear caused by sparks during commutation. In addition, an AC servo motor has a built-in encoder, which can "report" the motor's operating status to the driver at any time. The driver then uses the received "report" to control the motor's operation more precisely. Thus, AC servo motors have many advantages. However, they also have higher technical requirements and are more expensive. Most importantly, the tuning technology for AC servo motors has improved significantly. In other words, even a good motor can have many problems if not tuned properly. The rotor inside a servo motor is a permanent magnet. The U/V/W three-phase electricity controlled by the driver creates an electromagnetic field, causing the rotor to rotate under the influence of this magnetic field. Simultaneously, the motor's built-in encoder feeds back signals to the driver. The driver compares the feedback value with the target value and adjusts the rotor's rotation angle accordingly. The accuracy of a servo motor depends on the accuracy (line count) of the encoder.
4. What is a servo motor? What types are there? What are their working characteristics?
A: A servo motor, also known as an actuator motor, is used as an actuating element in automatic control systems. It converts received electrical signals into angular displacement or angular velocity output on the motor shaft. Servo motors are broadly classified into DC and AC servo motors. Their main characteristic is that they do not rotate when the signal voltage is zero, and their speed decreases uniformly as the torque increases.
Q: What are the functional differences between AC servo motors and brushless DC servo motors? A: AC servo motors are better because they use sinusoidal wave control, resulting in less torque ripple. DC servo motors use trapezoidal wave control. However, DC servo motors are simpler and cheaper.
Since the 1980s, with the development of integrated circuits, power electronics technology, and AC variable speed drive technology, permanent magnet AC servo drive technology has made remarkable progress. Leading electrical manufacturers worldwide have successively launched their own series of AC servo motors and servo drives, continuously improving and updating them. AC servo systems have become the main development direction of contemporary high-performance servo systems, putting the original DC servo systems at risk of obsolescence. Since the 1990s, commercially available AC servo systems worldwide have adopted fully digitally controlled sinusoidal wave motor servo drives. The development of AC servo drive devices in the transmission field is progressing rapidly. Compared with DC servo motors, the main advantages of permanent magnet AC servo motors are: (1) No brushes or commutators, therefore reliable operation and low maintenance requirements. (2) Easier stator winding heat dissipation. (3) Low inertia, making it easier to improve system speed. (4) Suitable for high-speed, high-torque operation. (5) Smaller size and weight for the same power.
Introduction to servo motors
Servo motors (or actuator motors) are widely used actuators in automatic control systems and computing devices. Their function is to convert received electrical signals into angular displacement or angular velocity of the motor shaft. Based on the type of current, servo motors can be divided into two main categories: DC and AC.
I. AC Servo Motor
1. Structure and Principle
The stator windings of an AC servo motor are similar to those of a single-phase asynchronous motor. Its stator has two windings spatially separated by 90° electrical angles: an excitation winding and a control winding. During operation, a constant AC excitation voltage is applied to the excitation winding, while a control voltage, whose magnitude or phase varies with the signal, is applied to the control winding. There are two rotor structures: squirrel-cage rotors and hollow cup rotors. The squirrel-cage rotor has the same structure as a typical squirrel-cage asynchronous motor rotor, but it is slender, and the rotor conductors are made of a high-resistivity material. This is to reduce the rotor's moment of inertia, increase the rapid response of the starting torque to the input signal, and overcome the self-rotation phenomenon. The stator of a hollow cup rotor AC servo motor consists of an outer stator and an inner stator. The structure of the outer stator is the same as that of a squirrel-cage AC servo motor stator, with two-phase windings placed in the iron core slots. The hollow cup rotor is made of a thin-walled cylindrical material (such as aluminum) and is placed between the inner and outer stators. The bottom of the cup is fixed on the rotating shaft. The cup arm is thin and light, with a thickness of generally 0.2-0.8mm, resulting in a small moment of inertia and fast and sensitive movement.
The working principle of an AC servo motor is similar to that of a single-phase asynchronous motor. LL is the excitation winding with a fixed voltage, and LK is the control winding powered by a servo amplifier. The two windings are 90° out of phase in space. If the phase difference between IL and Ik is 90°, and the magnetomotive force amplitudes of the two windings are equal, this state is called a symmetrical state. Similar to a single-phase asynchronous motor, the combined magnetic field generated in the air gap is a rotating magnetic field, and its speed is called the synchronous speed. The rotating magnetic field cuts relative to the rotor conductors, inducing a current in the rotor. The rotor current interacts with the rotating magnetic field to generate torque, causing the rotor to rotate. If the magnitude or phase difference of the current applied to the control winding is changed, the symmetrical state is disrupted, the rotating magnetic field weakens, and the motor speed decreases. The more asymmetrical the motor's operating state, the smaller the total electromagnetic torque. When the signal voltage on the control winding is removed, the motor immediately stops rotating. This is the difference between an AC servo motor and a regular asynchronous motor in operation.
AC servo motors have the following three speed control methods:
(1) Amplitude control: The phase difference between the control current and the excitation current remains constant at 90°, while the magnitude of the control voltage is changed.
(2) Phase control: The magnitude of the control voltage and the excitation voltage are kept constant at the rated value, and the phase of the control voltage is changed.
(3) Amplitude-phase control changes both the amplitude and phase of the control voltage simultaneously. The direction of rotation of the AC servo motor shaft changes with the phase reversal of the control voltage.
2. Working characteristics and applications
The operating characteristics of a servo motor are characterized by its mechanical and regulatory properties. With a constant control voltage, an increase in load leads to a decrease in speed; its regulatory characteristic is that with a constant load, the higher the control voltage, the higher the speed. Servo motors have three significant characteristics:
(1) High starting torque: Due to the high resistance of the rotor conductor, the critical slip Sm > 1. Once the control voltage is applied to the stator, the rotor starts running immediately.
(2) Wide operating range: It can operate stably within a slip range of 0 to 1.
(3) The phenomenon that the motor continues to rotate after the control signal disappears is called "self-rotation". Self-rotation destroys servo performance and should obviously be avoided.
When a servo motor is in normal operation, it enters single-phase operation mode once the control voltage is lost. Because the rotor conductor resistance is sufficiently high, the total electromagnetic torque is always a braking torque. When the motor rotates forward and loses the control voltage (Uk), the resulting torque is negative (0 < S < 1). Conversely, when it rotates in reverse and loses UK, the resulting torque is positive (1 < S < 2). It does not exhibit self-rotation and can brake automatically, quickly stopping operation. This is a key difference between AC servo motors and asynchronous motors.
Different types of AC servo motors have different characteristics. Squirrel-cage AC servo motors are characterized by low excitation current, small size, and high mechanical strength; however, they are not smooth enough at low speeds and exhibit vibration. Hollow-cup rotor AC servo motors have advantages such as simple structure, easy maintenance, low moment of inertia, smooth operation, low noise, no radio interference, and no vibration; however, they have a larger excitation current, are larger in size, the rotor is prone to deformation, and their performance is inferior to that of DC servo motors.
AC servo motors are suitable for low-power automatic control systems ranging from 0.1 to 100W, with frequencies including 50Hz and 400Hz. The squirrel-cage AC servo motor is the SL series. The hollow cup-shaped rotor AC servo motor is the SK series, used in systems requiring smooth operation.
II. DC Servo Motor
The basic structure of a DC servo motor is the same as that of a conventional separately excited DC motor. The difference lies in the armature current: the armature current of a DC servo motor is very small, commutation is not difficult, and therefore commutation poles are not required. Furthermore, the rotor is made slender with a small air gap, unsaturated magnetic circuit, and relatively high armature resistance. Based on the excitation method, they can be divided into electromagnetic and permanent magnet types. The magnetic field of an electromagnetic DC servo motor is generated by an excitation winding, and it is generally separately excited. The magnetic field of a permanent magnet DC servo motor is generated by a permanent magnet, eliminating the need for an excitation winding and excitation current, thus reducing size and losses. To meet the needs of various systems, many structural improvements have been made, leading to the development of low-inertia slotless armatures, hollow cup-shaped armatures, printed winding armatures, and brushless DC servo motors.
The working principle of an electromagnetic DC servo motor is the same as that of a separately excited DC motor. Therefore, electromagnetic DC servo motors have two speed control methods: armature control and field control. Permanent magnet DC servo motors, of course, only have armature control speed regulation. Because the performance of field control speed regulation is inferior to armature control speed regulation, DC servo motors generally use armature control speed regulation. The direction of rotation of the DC servo motor shaft changes with the polarity of the control voltage.
The mechanical characteristics of a DC servo motor are similar to those of a separately excited DC motor, i.e., n = n0 - αT. When the excitation is constant, there is a set of decreasing parallel straight lines for different voltages Ua.
DC servo motors are suitable for automatic control systems with relatively high power (1-600W). Compared with AC servo motors, they have better speed regulation linearity, smaller size, lighter weight, higher starting torque, and higher output power. However, their structure is complex, especially their low-speed stability is poor, and sparks can cause radio interference. In recent years, low-inertia slotless armature motors, hollow cup armature motors, printed winding armature motors, and brushless DC servo motors have been developed to improve fast response capabilities and meet the needs of automatic control systems, such as television cameras, tape recorders, and X-Y function recorders.
Permanent magnet AC servo motor
Since the 1980s, with the development of integrated circuits, power electronics technology, and AC variable speed drive technology, permanent magnet AC servo drive technology has made remarkable progress. Leading electrical manufacturers worldwide have successively launched their own series of AC servo motors and servo drives, continuously improving and updating them. AC servo systems have become the main development direction of contemporary high-performance servo systems, putting the traditional DC servo system at risk of obsolescence. Since the 1990s, commercially available AC servo systems worldwide have adopted fully digitally controlled sinusoidal wave motor servo drives. The development of AC servo drive devices in the transmission field is progressing rapidly. Compared with DC servo motors, permanent magnet AC servo motors have the following main advantages:
(1) It has no brushes or commutator, so it is reliable in operation and requires little maintenance.
(2) Stator windings are relatively easy to dissipate heat.
(3) Low inertia makes it easy to improve the speed of the system.
(4) Suitable for high-speed and high-torque working conditions.
(5) It has a smaller size and weight for the same power.
Since the Indramat division of Rexroth GmbH of MANNESMANN in Germany officially launched the MAC permanent magnet AC servo motor and drive system at the Hannover Trade Fair in 1978, it marked the entry of this new generation of AC servo technology into the practical application stage. By the mid-to-late 1980s, various companies had complete product series. The entire servo device market shifted to AC systems. Early analog systems had shortcomings in areas such as zero drift, interference immunity, reliability, accuracy, and flexibility, and could not fully meet the requirements of motion control. In recent years, with the application of microprocessors and new digital signal processors (DSPs), digital control systems have emerged, where the control part can be completely controlled by software. These are called permanent magnet AC servo systems, also known as analog or digital permanent magnet AC servo systems.
To date, most high-performance electric servo systems employ permanent magnet synchronous AC servo motors, and the control drives typically utilize fully digital position servo systems for fast and accurate positioning. Typical manufacturers include Siemens (Germany), Kollmorgen (USA), and Panasonic and Yaskawa (Japan).
Yaskawa Electric Works of Japan introduced small AC servo motors and drives. The D series is suitable for CNC machine tools (maximum speed 1000 r/min, torque 0.25–2.8 Nm), while the R series is suitable for robots (maximum speed 3000 r/min, torque 0.016–0.16 Nm). Later, six more series—M, F, S, H, C, and G—were introduced. In the 1990s, new D and R series were launched. The old series were changed from rectangular wave drive and 8051 microcontroller control to sine wave drive, 80C, 154 CPU, and gate array chip control, reducing torque ripple from 24% to 7% and improving reliability. In just a few years, a relatively complete system of eight series (power range 0.05–6 kW) was formed, meeting the diverse needs of machine tools, handling mechanisms, welding robots, assembly robots, electronic components, processing machinery, printing presses, high-speed winding machines, and wire winding machines.
Fanuc, a Japanese company famous for producing CNC machine tool systems, in the mid-1980s
During this period, they also launched the S series (13 specifications) and L series (5 specifications) permanent magnet AC servo motors. L series
It has a small moment of inertia and mechanical time constant, making it suitable for position servo systems that require particularly fast response.
Other Japanese manufacturers, such as Mitsubishi Electric (HC-KFS, HC-MFS, HC-SFS, HC-RFS and HC-UFS series), Toshiba Seiki (SM series), Okuma Iron Works (BL series), Sanyo Electric (BL series), and Tateishi Electric (S series), have also entered the competition for permanent magnet AC servo systems.
The MAC series of AC servo motors from the Indramat division of Rexroth GmbH in Germany has 7 frame sizes and 92 specifications.
The Siemens IFT5 series of three-phase permanent magnet AC servo motors are divided into two main categories: standard and short models, with a total of 8 frame sizes and 98 specifications. It is claimed that this series of AC servo motors weighs only half as much as the IHU series of DC servo motors with the same output torque. The matching 6SC61 series transistor pulse width modulation drivers can control up to six axes of motors.
Bosch GmbH of Germany manufactures AC servo motors of the SD series (17 specifications) of ferrite permanent magnets and the SE series (8 specifications) of rare earth permanent magnets, as well as drive controllers of the ServodynSM series.
Gettys, a well-known American servo device manufacturer, was once a division of Gould Electronics (Motion Control Division), producing the M600 series AC servo motors and the A600 series servo drives.
Drives. Later merged into AEG, restored the Gettys name, and launched the A700 fully digital AC servo system.
Allen-Bradley (AB) of the United States manufactures the Model 1326 ferrite permanent magnet AC servo motor and the Model 1391 AC PWM servo controller. The motors include 3 frame sizes with a total of 30 specifications.
Industrial Drives (ID) is the industrial drive division of the renowned American company Kollmorgen. It previously produced brushless servo motors in three series (BR-210, BR-310, and BR-510) with a total of 41 specifications, as well as BDS3 servo drives. Since 1989, it has introduced a completely new series of Goldline permanent magnet AC servo motors, including three main categories: B (low inertia), M (medium inertia), and EB (explosion-proof). These are available in five frame sizes: 10, 20, 40, 60, and 80, with 42 specifications in each category. All motors use neodymium iron boron permanent magnets, with torque ranging from 0.84 to 111.2 Nm and power ranging from 0.54 to 15.7 kW. The corresponding drives include the BDS4 (analog), BDS5 (digital, with position control), and SmartDrive (digital) series, with a maximum continuous current of 55 A. The Goldline series represents the latest advancement in contemporary permanent magnet AC servo technology.
Inland, Ireland, formerly an overseas division of Kollmorgen, is now part of AEG and is renowned for producing DC servo motors, DC torque motors, and servo amplifiers. It manufactures 17 models of SmCo permanent magnet AC servo motors in three frame sizes (BHT1100, 2200, and 3300) and eight types of controllers.
The French Alsthom Group manufactures the LC series (long type) and GC series (short type) at its Parvex plant in Paris.
There are 14 specifications of AC servo motors, and we also manufacture the AXODYN series of drives.
The former Soviet Union developed two series of AC servo motors for servo control of CNC machine tools and robots. The ДBy series uses ferrite permanent magnets, has two frame sizes, each with three core lengths and two winding configurations, totaling 12 specifications, with a continuous torque range of 7–35 N·m. The 2ДBy series uses rare-earth permanent magnets, has six frame sizes and 17 specifications, with a torque range of 0.1–170 N·m, and is paired with a 3ДБ type controller.
In recent years, Panasonic has launched the all-digital MINAS series of AC servo systems. Among them, the permanent magnet AC servo motors include the MSMA series of small inertia type, with power ranging from 0.03 to 5kW, totaling 18 specifications; the medium inertia type includes three series: MDMA, MGMA, and MFMA, with power ranging from 0.75 to 4.5kW, totaling 23 specifications; and the MHMA series of large inertia motors, with power ranging from 0.5 to 5kW, and 7 specifications.
Samsung Corporation of South Korea has recently developed a range of fully digital permanent magnet AC servo motors and drive systems. Among them, the FAGA AC servo motor series includes various models such as CSM, CSMG, CSMZ, CSMD, CSMF, CSMS, CSMH, CSMN, and CSMX, with power ranging from 15W to 5kW.
The Powerrate is now commonly used as a quality factor for servo motors to measure and compare the dynamic response performance of various AC/DC servo motors and stepper motors. The Powerrate represents the ratio of the motor's continuous (rated) torque to its rotor moment of inertia.
According to the calculation and analysis based on the power change rate, the technical specifications of permanent magnet AC servo motors are best of the American ID Goldline series, followed by the German Siemens IFT5 series.
