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180 - Analysis of SR Motor Dynamic Characteristics 180 - Analysis of SR Motor Dynamic Characteristics Module:DP 2014-04-25
With the skyrocketing prices of rare earth magnets, expectations have been rising for SR (switched reluctance) motors because they have a motor format that does not use permanent magnets. SR motors have a simple structure that can achieve solid performance at a low price. However, torque generation depends only upon the saliency between the stator and rotor, so torque variations are extremely large and cause vibration and noise, meaning that the use applications are limited. On the other hand, because of the skyrocketing prices of rare earth metals, the improvement in current control technology, the possibility of optimized designs thanks to magnetic field analysis, and the rising ability to reduce challenges, SR motors are being re-examined.
SR motors create their excitation state by alternating between opening and closing switches in accordance with the position of the rotor's rotation, however the timing of the alternating causes major changes in the torque properties. Also, it is important not only to increase the torque average and torque constant, but also to consider the optimum switch timing to control vibration and noise.
This example presents how to carry out an analysis with different switch timings to evaluate torque and current in SR motors.
179 - Analysis of SR Motor Static Characteristics 179 - Analysis of SR Motor Static Characteristics Module:DP 2013-01-23
With the skyrocketing prices of rare earth magnets, expectations have been rising for SR (switched reluctance) motors because they have a motor format that does not use permanent magnets. SR motors have a simple structure that can achieve solid performance at a low price. However, torque generation depends only upon the saliency between the stator and rotor, so torque variations are extremely large and cause vibration and noise, meaning that the use applications are limited. On the other hand, because of the skyrocketing prices of rare earth metals, the improvement in current control technology, the possibility of optimized designs thanks to magnetic field analysis, and the rising ability to reduce challenges, SR motors are being re-examined.
SR motors operate using the nonlinear region of a magnetic steel sheet, so because the inductance displays nonlinear behavior, it is impossible to carry out advanced projections that are accurate with calculation methods that follow linear formulas. Consequently, it becomes necessary to use the finite element method (FEM), which can handle nonlinear magnetic properties in material and minute geometry.
This example presents an evaluation for each rotor position of the effect on flux linkage (shown as I-Psi characteristics below) when excitation current is changed.
167 - Iron Loss Analysis of a Three Phase Induction Motor 167 - Iron Loss Analysis of a Three Phase Induction Motor Module:DP,LS 2013-06-27
An induction motor is a motor in which the rotating magnetic field of the stator coils causes induced current to flow in an auxiliary conductor, which produces force in the rotational direction.
Induction motors are widely used in everything from industrial machines to home appliances because they have a simple construction without parts that experience wear from abrasion, and can be used simply by connecting them to a power source.
Improved efficiency in induction motors is an important theme. Iron loss, a cause of lower efficiency along with primary and secondary copper loss, must be reduced in order to improve efficiency. The relative importance of iron loss tends to grow especially with higher rotations due to the inverter drive, so it is helpful to estimate the complex iron loss distribution inside the core.
This Application Note presents an example of how to find the iron loss in the stator core and rotor core at a rotation speed of 3,300 r/min.
161 - Line Start Analysis of a Three-phase Induction Machine161 - Line Start Analysis of a Three-phase Induction Machine
Module:DP2012-08-31
The simplest method for starting an induction motor is a line start that connects the motor to a direct power supply. For a line start, the static impedance is small compared to impedance during rated operation, so a large current flows during the initial start-up.
The large current flowing through both the primary and secondary sides during start-up causes intense magnetic saturation near the induction motor's gap. This magnetic saturation results in reduced impedance, so the starting current grows even larger. The size of the starting current affects the voltage source capacity connected to the induction motor, as well as both the electromagnetic force and heat capacity that operate on the motor's coils. This is why it is beneficial to investigate the starting performance of an induction motor with the finite element method (FEM), which can account for local magnetic saturation.
This Application Note presents an analysis that simulates the line start of an induction motor and obtains the starting performance of its rotation speed variations.
159 - Sensitivity Analysis of Dimensional Tolerance in an SPM Motor159 - Sensitivity Analysis of Dimensional Tolerance in an SPM Motor
Module:DP2013-10-28
The corners of magnets used in surface permanent magnet (SPM) motors can be filleted, chamfered, etc. However, it is difficult to maintain exactly the same production in the manufacturing process, and some variation among finished products will occur. Dimensional tolerance is set so as to eliminate the effects of these variations on motor performance.
There are tradeoffs between dimensional tolerance, performance, and cost, so it is important to investigate these at the design stage. With numerical analysis using the finite element method (FEM), it is possible to evaluate the sensitivity of motor performance, such as torque, by simply changing the dimensions.
This Application Note presents how to assume a dimensional tolerance of ±0.4 mm for a chamfer, and find out whether changing dimensions within the tolerance range has an effect on motor performance by comparing cogging torque and induced voltage.
139 - Power Transmission Analysis Using Magnetic Resonance Phenomena 139 - Power Transmission Analysis Using Magnetic Resonance Phenomena Module:FQ 2014-02-27
Recently, magnetic resonance is gaining attention as a new type of wireless transmission technology. Magnetic resonance differs from conventional types of electromagnetic induction transmission that are widely used today in that the axes of the transmission and receiving coils do not need to be aligned and in that it allows efficient transmission at a distance of several meters. A design for the coil geometry and circuit that is optimized for the frequency being used is necessary to make the transmitting and receiving sides resonate and thus transmit power.
It is very difficult to use measurement to visualize how magnetic field is being generated, and is therefore transmitting power, in the space between the transmitting side and the receiving side. Reproducing the power transmission state using analysis can help with designing optimized coils.
This Application Note presents how to confirm the power transmission efficiency and the magnetic flux density distribution.
129 - Analysis of a PM Stepper Motor Accounting for Magnetization129 - Analysis of a PM Stepper Motor Accounting for Magnetization
Module:ST,TR2013-09-03
Stepper motors are commonly used for positioning in printers and digital cameras. In PM stepper motors, the motor's characteristics are determined through design of the magnetization state of the permanent magnet used. It is necessary to accurately evaluate this magnetization state in order to improve the precision of estimations of a PM stepper motor's characteristics.
Detailed measurements of the magnetization distribution inside a magnet are difficult to make. However, it is possible to accurately find the magnet's magnetization because it can be obtained through analysis of the magnetization field from the magnetization device, using the finite element method (FEM).
In this analysis, a magnetization device model is created and a magnet is magnetized. The magnetization distribution and surface magnetic flux density of the magnetized magnet, and the induced voltage of a PM stepper motor with the magnetized magnet integrated into it, are then obtained.
127 - Resistance Heating Analysis of Steel 127 - Resistance Heating Analysis of Steel Module:FQ,HT 2013-12-17
Deformation occurs when large metal parts such as shafts undergo machining, causing their material properties to worsen. Because of this, these material properties are restored by eliminating machining deformations using thermal processing, which returns the metal structure to its standard condition. It is necessary to heat the whole part to the same temperature in order to restore the metal's overall properties with thermal heating, and ohmic heating is often used for this purpose. It is helpful to measure the temperature distribution in advance with an investigation of heating conditions.
Evaluation with analysis based on the finite element method (FEM) is necessary to find whether a product with a 3D geometry is heated uniformly by a given electrode configuration.
This Application Note presents how to obtain the temperature distribution, temperature variations, and heat flux distribution in a body heated by ohmic heating.
125 - Thrust Force Analysis of a Shaft Motor125 - Thrust Force Analysis of a Shaft Motor
Module:DP2011-01-17
Shaft motors have been widely used in motion control systems and machine tools due to their capability for high-speed performance, high acceleration and deceleration as well as accurate positioning. The magnet is arranged in the center of the coil and the magnetic flux that is produced can be efficiently converted into thrust force.
This example presents the use of a magnetic field analysis to obtain the thrust force of a shaft motor.
124 - Cogging Torque Analysis of an SPM Motor Accounting for Uneven Stator Diameter124 - Cogging Torque Analysis of an SPM Motor Accounting for Uneven Stator Diameter
Module:DP,DS2013-06-27
When a motor is assembled, the inner diameter of the stator can become uneven because of fabrication errors, shrink fitting, press fitting, etc. Cogging torque increases due to this unevenness, causing vibration and noise.
When a frame is pressed onto a stator core, and when the frame thickness is not uniform in the circumferential direction, the fitting pressure has a distribution in the circumferential direction, and the inner diameter of the stator can become uneven. In order to deal with vibration and noise, it is necessary to accurately grasp the amount of unevenness and evaluate the cogging torque in relation to this unevenness. The stator's inner-diameter unevenness due to press fitting depends on the frame's geometry, so it can be accurately grasped using the finite element method (FEM).
This Application Note presents how to obtain the cogging torque with and without uneven displacement in the stator teeth, based on the displacement obtained in an analysis of stress from press fitting.
122 - Inductance Analysis of an IPM Motor - d/q-axis Inductance Obtained by Actual Measurement -122 - Inductance Analysis of an IPM Motor - d/q-axis Inductance Obtained by Actual Measurement -
Module:DP2013-10-28
Evaluating the inductance characteristics along the d/q-axis is important when analyzing the saliency of a rotor in an IPM motor. With actual measurements, it is possible to calculate the inductance in the d-axis and q-axis by measuring the no-load magnetic flux or the voltage and current with a three-phase current flowing when the motor is in actual operation. If it cannot be measured while the motor is operating, an LCR meter can be entered in two phases when the rotor is in a stationary state. However, current conditions are different between three phases and two phases, so the motor will express different characteristics during actual drive, especially when it is strongly affected by magnetic saturation. For this reason, the analysis contents need to be determined according to the situation of the actual measurements when comparing the measurements with an analysis.
This Application Note presents an analysis that obtains d/q-axis inductance in an IPM motor while assuming actual measurements in a stationary rotor.
121 - Output Analysis of a Salient-Pole Synchronous Generator121 - Output Analysis of a Salient-Pole Synchronous Generator
Module:DP2013-04-26
Salient-pole synchronous generators are used in hydroelectric generators and the like. Power is generated in the stator coils (armature) by a field current flowing in the rotor coils and the rotor rotating.
Reactions occur between the field current and the armature current that either strengthen or weaken the magnetic flux depending on the power factor of the connected load of a salient-pole synchronous generator. This causes the operating point of the magnetic circuit inside the generator to change, which affects the output. The core normally has nonlinear magnetic properties, so an evaluation of the magnetic circuit with magnetic field analysis, which can handle nonlinear magnetic properties, is useful.
This Application Note presents the use of a magnetic field analysis to obtain the magnetic flux density distribution, no-load saturation curve, and output of a salient-pole synchronous generator.
120 - Thermal Demagnetization Analysis of an SPM Motor 120 - Thermal Demagnetization Analysis of an SPM Motor HOT! Module:DP 2014-08-26
Exactly how to resolve the problem of rising temperatures is a vital issue when trying to achieve an improvement in a motor's efficiency and output. Among the materials used in a motor, the magnet experiences the greatest variations in properties in relation to temperature. In the case of rare-earth magnets, demagnetization can occur within tens of degrees above 100 deg C. Whether they demagnetize or not depends on the reverse magnetic field applied and the temperature. They still have some resistance if either the temperature is raised only or if a reverse magnetic field is applied only, but the combination of the two causes a great reduction in resistance. A large current flows in the coils when the motor is overloaded and is producing a lot of torque, which leads to a large reverse magnetic field and heat, increasing the possibility of demagnetization. Solutions to this problem include heat-resistant magnets and increased motor size, but these lead to trade-off issues during the design stage because of the larger size and higher cost.
In order to carry out a precise evaluation of demagnetization, it is necessary to get a definite grasp of areas where a reverse magnetic field occurs and the materials' demagnetization properties. With magnetic field analysis simulation using the finite analysis method (FEM), it is possible to calculate the reverse magnetic field and determine whether magnets and other parts demagnetize due to reverse magnetic field, taking material demagnetization properties into account.
This Application Note presents how to change the temperature of permanent magnets in an analysis, and then evaluate the effects on the torque waveform, magnetic flux density distribution, etc.
116 - Operating Time Analysis of an Injector by Evaluating the Reduction in Eddy Currents116 - Operating Time Analysis of an Injector by Evaluating the Reduction in Eddy Currents
Module:TR2013-06-17
A solenoid type injector used in engines opens a valve and injects fuel by moving a plunger with magnetic force created by an electromagnet. Injectors in engines need to respond quickly to applied voltage in order to control the amount of fuel flow and improve fuel efficiency.
In solenoid injectors, one of the reasons for slow response is eddy currents, which are produced when the magnetic flux generated by current flow undergoes time variations. The eddy currents are generated in a direction that inhibits changes in the magnetic flux, causing a delay in the initial rise of the attraction force when the current begins to flow. This reduces the injector's responsiveness. JMAG makes it possible to account for effects from eddy currents and obtain an injector's responsiveness by running a transient response analysis. Identifying the places where eddy currents are generated enables a designer to study how responsiveness can be improved.
This Application Note explains how to apply direct current voltage to a solenoid injector and obtain its response characteristics by accounting for effects from eddy currents. The effectiveness of slots added to reduce eddy currents are evaluated by comparing the analysis results with a model without slots added.
111 - Starting Performance Analysis of a Universal Motor111 - Starting Performance Analysis of a Universal Motor
Module:DP2009-04-14
A universal motor is a motor that rotates on both direct and alternating currents. A universal motor is used in home appliances and industrial machines because these motors are robust and compact with a simple construction. However, problems such as vibration and a reduction in starting torque caused by the cogging torque occur as the size of the motor becomes smaller.
Evaluating the starting performance of a universal motor at the design stage is necessary to resolve these problems.
This example presents the use of a magnetic field analysis to obtain the speed versus time graph, the current waveform, and the torque versus time graph for a universal motor.
109 - Operating Time Analysis of an Electromagnetic Relay Accounting for Eddy Currents109 - Operating Time Analysis of an Electromagnetic Relay Accounting for Eddy Currents
Module:TR2013-10-28
Electromagnetic relays are devices that use an electromagnet to physically connect and disconnect contact points. Magnetic flux is generated from the magnetomotive force, which is expressed as the product of the number of turns in the coil and the current that is applied to the coil. This flux produces an attraction force in the movable core, making the relay close.
To put it simply, the attractive force is determined from the area of the gap between the movable core and the stator core and the size of the magnetic flux density produced in said gap. With a relay whose movable core does not move linearly, however, it is a difficult problem to predict the magnetic flux density in the gap because it does not become parallel. The nonlinear magnetic properties of the iron core and yoke also affect the magnetic flux density in the gap. With a JMAG magnetic field analysis, it is possible to obtain the attraction force of the movable core while accounting for these factors. One of the reasons that the response is delayed in electromagnetic relays is eddy currents, which are produced when the magnetic flux generated by current flow undergoes time variations. The eddy currents are generated in a direction that inhibits changes in the magnetic flux, causing a delay in the initial rise of the attraction force when the current begins to flow. This reduces the injector's responsiveness. JMAG makes it possible to account for the effects from eddy currents and obtain an electromagnetic relay's responsiveness by running a transient response analysis.
This Application Note presents the use of the motion equation function to evaluate the operating time of an electromagnetic relay with DC voltage drive. Eddy currents generated in the core are considered for this purpose.
103 - Efficiency Analysis of a Permanent Magnet Synchronous Motor103 - Efficiency Analysis of a Permanent Magnet Synchronous Motor
Module:DP,LS2013-04-26
A permanent magnet synchronous motor rotates by converting electric energy to mechanical energy.
The important thing when converting energy is efficiency indicated by the power factor for the amount of current effectively used, as well as the percentage of output versus input.
Evaluating the power factor and input/output characteristics that account for efficiency is necessary to design a highly efficient motor.
This example presents the use of a magnetic field analysis to evaluate the efficiency of a permanent magnet synchronous motor.
94 - Analysis of Detent Torque of a PM Stepper Motor94 - Analysis of Detent Torque of a PM Stepper Motor
Module:TR2013-02-28
PM stepper motors are commonly used for positioning of moving parts in small devices such as printers and video equipment. In order for its drive to function with an open loop, the most important characteristics for a stepper motor are controllability and holding torque, and not the motor's output. Therefore, the desired characteristics are detent torque, which is a non-excitation holding torque, and stiffness torque, which is an excitation holding torque.
A PM stepper motor is made up of a multi-pole magnetized rotor and offset inductors for each phase. In order to reduce their size and number of parts, claw pole inductors are made from folded steel sheet. Because of this, the flow of magnetic flux is three dimensional, so it is necessary to carry out a 3D electromagnetic field analysis using the finite element method (FEM) to proceed with an accurate preliminary study.
This Application Note describes how the detent torque can be calculated for a PM stepper motor.
93 - Cogging Torque Analysis of a Motor with 8 Poles and 9 Slots Accounting for Eccentricity93 - Cogging Torque Analysis of a Motor with 8 Poles and 9 Slots Accounting for Eccentricity
Module:DP2010-08-31
Eccentricity can occur on the center axis or the rotation axis of a motor. It is advantageous to evaluate the effects of eccentricity because it can cause vibrations and noise and break the symmetry of the magnetic flux density distribution and the electromagnetic force.
This example presents the use of a magnetic field analysis to obtain the cogging torque and electromagnetic force with and without eccentricity.
89 - Stiffness Torque Analysis of a PM Stepper Motor89 - Stiffness Torque Analysis of a PM Stepper Motor
Module:TR2013-10-28
PM stepper motors are commonly used for positioning of moving parts in small devices such as printers and video equipment. In order for its drive to function with an open loop, the most important characteristics for a stepper motor are controllability and holding torque, and not the motor's output. Therefore, the desired characteristics are detent torque, which is a non-excitation holding torque, and stiffness torque, which is an excitation holding torque.
A PM stepper motor is made up of a multi-pole magnetized rotor and offset inductors for each phase. In order to reduce their size and number of parts, claw pole inductors are made from folded steel sheet. Because of this, the flow of magnetic flux is three dimensional, so it is necessary to carry out a 3D electromagnetic field analysis using the finite element method (FEM) to proceed with an accurate preliminary study.
This Application Note describes how the stiffness torque at 0.5 A of current can be calculated for a PM stepper motor.
80 - Cogging Torque Analysis of an SPM Motor with Skewed Magnetization80 - Cogging Torque Analysis of an SPM Motor with Skewed Magnetization
Module:TR2013-06-27
Reductions in vibration and noise are being sought after because they are a cause of torque variations in motors, and demands for reduction are particularly strong with motors that are used in machine tools and power steering. Cogging torque, which is a torque variation that is produced when there is no current, is generated because the electromagnetic force produced in the gap changes according to the rotor's rotation. This makes it necessary to apply skew to the stator and rotor and come up with innovative geometry for the magnet and stator in order to reduce torque variations by limiting variations in the electromagnetic force. Applying skew reduces the cogging torque, but it also brings disadvantages such as producing force in the thrust direction and generating eddy currents from the magnetic flux that links in the lamination direction.
Consequently, in order to accurately evaluate a motor that has skew applied, one needs a magnetic field analysis simulation that uses the finite element method (FEM), which can account for a detailed 3D geometry, instead of studies that use the magnetic circuit method or a 2D magnetic field analysis.
This Application Note presents the use of a magnetic field analysis to obtain the flux density distribution, cogging torque, and induced voltage of an SPM motor that has skewed magnetization applied to its magnet.
67 - Analysis of AC Loss in a Superconductor67 - Analysis of AC Loss in a Superconductor
Module:TR2010-08-31
When superconductors are in the superconducting state, in which temperature, magnetic field and current become lower than a critical value, its electrical resistance becomes zero. Although superconducting wire rod requires a cooling system to maintain a low-temperature state, having features such as high current density and extremely low loss, it has a lot of advantages in terms of energy and environment. The electrical resistance in the superconductor becomes zero, when DC is applied, but when AC is applied, loss is caused in a superconductor. In JMAG, the AC loss in a superconductor can be obtained. This note presents the use of magnetic field analysis to obtain the AC loss in a superconductive filament.
66 - Operating Time Analysis of  an Injector66 - Operating Time Analysis of an Injector
Module:DP2014-06-19
A solenoid type injector used in engines opens a valve and injects fuel by moving a plunger with magnetic force created by an electromagnet. Injectors in engines need to respond quickly for applied voltage to improve fuel consumption by maintaining the amount of fuel flow.
In solenoid injectors, one of the reasons that the response is delayed is eddy currents, which are produced when the magnetic flux generated by current flow undergoes time variations. The eddy currents are generated in a direction that inhibits changes in the magnetic flux, causing a delay in the initial rise of the attraction force when the current begins to flow. This reduces the injector's responsiveness. JMAG makes it possible to account for the effects from eddy currents and obtain an injector's responsiveness by running a transient response analysis. Identifying the places where eddy currents are generated enables a designer to study whether or not responsiveness can be improved.
This Application Note explains how to apply direct current voltage to a solenoid injector and obtain its response characteristics by accounting for effects from eddy currents.
65 - Static Thrust Analysis of a Voice Coil Motor 65 - Static Thrust Analysis of a Voice Coil Motor Module:TR 2013-10-28
Linear actuators are used in machine tools because of their high-speed performance, high acceleration and deceleration, and accurate positioning. There are coreless types of linear actuators, as well. They generally have a smaller thrust force than core linear actuators, but they do not produce cogging, so they only have a small amount of thrust variation. Because of this property, they are used in fields where high-accuracy positioning is necessary, like with head drives of packaging machines or the slight movements of precision stages.
Static thrust variations at the translation position of the actuator have an effect on determining the position accurately. The static thrust is determined by the amount of current, so its current characteristics need to be obtained.
This Application Note explains how to obtain the current characteristics and the translation position characteristics of the static thrust in a voice coil motor, which is a type of coreless linear actuator.
64 - Thrust Force Analysis of a Coreless Linear Motor64 - Thrust Force Analysis of a Coreless Linear Motor
Module:TR2013-10-28
Linear motors are widely used for carrier devices and machine tools because of their high-speed performance, high acceleration and deceleration, and accurate positioning. Among them there is a type of motor called a coreless linear motor. Coreless linear motors generally have a smaller thrust force than core linear motors, but they do not produce cogging, so they only have a small amount of thrust variation. They are used for linear motor stages and electronic packaging machines to make use of this property.
Because the thrust variations in linear motors are small, they can be hard to predict and measure at the design stage. With the finite element method (FEM), it is possible to obtain thrust variations with accuracy even when they are small, as is the case with a coreless linear motor.
This Application Note explains how to obtain the thrust variations in a coreless linear motor when it is driven with a three-phase alternating current.
62 - Attractive Force Analysis of a Solenoid Valve62 - Attractive Force Analysis of a Solenoid Valve
Module:DP2013-10-28
Solenoid valves move their iron cores in a translational direction, and are used to adjust the inflow and outflow amounts of liquids and gasses. Running current through the coil forms an electromagnet, which generates an electromagnetic attraction force between the mover and stator. A high level of responsiveness is required to open and close the valve, so the power supply and valve used in the drive need to be evaluated to determine whether they fulfill the required responsiveness and attraction force.
The attraction force is determined from the size of the current, the arrangement of the iron core, and the material properties. However, the actual flow of magnetic flux is complex, and even if the current is increased, phenomena may occur such as the attractive force not being proportional to the current due to the effects of magnetic saturation in the core. A magnetic field analysis simulation using the finite element method (FEM) is useful in studying these kinds of behaviors.
This Application Note obtains the attraction force at each position of the movable core.
61 - Current Distribution Analysis of a Choke Coil61 - Current Distribution Analysis of a Choke Coil
Module:DP,TS2013-01-28
A choke coil is an electric component that is intended to filter high-frequency current.
The current in a choke coil's interior produces local heat generation because of the skin effect, proximity effect, and current offsets caused by leakage flux near the gap. From a heat resistant design standpoint, visual confirmation of detailed current distribution using a finite element analysis (FEA) is useful because it provides feedback for the design.
This Application Note explains a case example that obtains the current distribution in a choke coil.
58 - Efficiency Analysis of an IPM Motor58 - Efficiency Analysis of an IPM Motor
Module:DP,LS2013-10-28
An IPM motor's features are in its rotor geometry, where its magnets are embedded. When the stator's rotating magnetic field is applied in a direction that runs perpendicular to the rotor magnets (the q-axis) the motor operates like a normal SPM motor. When the current phase is displaced and the d-axis component is applied, however, the motor operates so that the magnetic fields in the rotor magnets are weakened. This is called field weakening. In an SPM motor the d-axis current operates enough to weaken the magnetic field, so the rotation speed increases but the torque decreases. However, the rotor geometry in an IPM motor is created so that there is a difference in inductance between the d-axis and q-axis, so it is possible to generate torque with the d-axis current, which weakens the magnets. This makes it possible to recover the part weakened by the flux. Consequently, an IPM motor achieves a greater range of operation by incorporating field weakening controls.
For this reason an IPM motor's characteristics depend greatly on its rotor geometry, so studies using the magnetic circuit method are difficult. In order to perform an advance design study accurately, an electromagnetic field analysis using the finite element method is necessary.
This Application Note presents the use of magnetic field analysis to obtain the efficiency of an IPM motor in each current phase with a rotation speed of 1800 rpm and the current amplitude of 4.0 A when the motor is driven by sinusoidal wave current.
55 - Integrated Magnetization Analysis of an IPM Motor55 - Integrated Magnetization Analysis of an IPM Motor
Module:DP,ST2013-10-28
Interior permanent magnet (IPM) motors often use strong rare earth magnets. They have poor workability, however, because the magnets are inserted into the rotor's small gaps during the assembly process. After the magnets have been inserted the rotor generates a strong magnetic field, which means that the workability when embedding it into the stator gets worse, as well. This is why in some cases they assemble the magnets while still in an unmagnetized state and magnetize them after they have been assembled. This construction method is called integrated magnetization. Using this means of construction can improve the assembly process a great deal, but there is also the possibility that the magnets will not be completely magnetized.
Consequently, first one needs to confirm whether or not integrated magnetization is even possible, and then from there to estimate the electrical power that the equipment needs for magnetization.
Using a magnetic field analysis simulation with the finite element method (FEM) provides the ability to change the making current amount and yoke geometry as magnetization conditions, as well as to account for magnetic saturation and evaluate whether or not the magnets are completely magnetized.
This Application Note explains how to determine the changes that occur in a magnetizing field if the making current is changed during magnetization, as well as how to obtain the induced voltage and cogging torque in the motor using the aforementioned magnets.
54 - Analysis of the Cogging Force of a Moving Coil Linear Motor54 - Analysis of the Cogging Force of a Moving Coil Linear Motor
Module:TR2013-06-27
Linear motors have been widely used in carrier devices and the drive units of machine tools due to their capability for high acceleration and deceleration, as well as their accurate positioning. In order to improve performance people are trying to obtain a large thrust force in order to enhance responsiveness, but one also needs to fulfill the demand for the trade-off of reducing thrust force variations and the attraction force. There are also times when skew is added to the magnets because of requirements to reduce thrust force variation.
In order to obtain a large thrust force, the material's nonlinear magnetic properties and the magnet's demagnetization characteristics need to be accounted for, and they need to be analyzed after modeling a detailed geometry in order to evaluate thrust force variations. This is why the characteristics need to be studied with a magnetic field analysis simulation based on the finite element method (FEM).
This Analysis Note explains how to obtain the magnetic flux density distribution and cogging in a moving coil linear motor with skew applied to its magnets.
46 - Sensitivity Analysis of the Magnetization Pattern of an SPM Motor46 - Sensitivity Analysis of the Magnetization Pattern of an SPM Motor
Module:DP,ST2013-04-26
The magnet in a surface permanent magnet (SPM) motor is arranged on the rotor's surface, facing the stator. The motor produces torque from the interaction between the magnetic field produced by the magnet and the magnetic field produced from the excitation coil. Cogging torque, which is generated during no-load rotation, depends largely on the magnet's magnetizing state. Adjusting the magnet's magnetization pattern makes it possible to reduce the cogging torque, which lowers efficiency and causes vibration and noise.
In order to control the magnetization pattern in the magnet of an actual machine precisely, a great number of magnetization devices is required. This makes a real machine hard to control, but with a magnetic field analysis simulation that uses the finite element method (FEM), it is possible to estimate how the cogging torque in the physical phenomenon will change by simply setting the magnetization pattern. Once the optimum magnetization pattern has been found, studying the magnetization method can lead to a reduction in development cost.
This Application Note presents the use of a magnetic field analysis to obtain the surface flux density for radial pattern, parallel anisotropic pattern, and polar anisotropy pattern magnets. It also displays the changes in induced voltage and cogging torque caused by differences in the magnetization patterns.
43 - Torque Analysis of a Coreless Motor43 - Torque Analysis of a Coreless Motor
Module:TR2013-01-28
As their name implies, coreless motors have a rotor that lacks a core and is made of only a coil. For this reason, there is no core to produce iron loss in the rotor, and its moment of inertia is small. They can be controlled easily because their characteristics are linear and they have small torque ripples, but they are not versatile enough to produce a large amount of torque. This is why they are often used in small precision equipment that requires high rotation speeds and good responsiveness. The rotor coil is hard to construct because it is made of only a coil. It is important to design the coil's twist angle to be able to produce torque. The model needs to be made precisely because coreless motors are used in compact equipment and because the detailed geometry of the parts can affect the characteristics.
In order to carry out these evaluations, the coil's twist needs to be accounted for accurately in three dimensions. An electromagnetic field analysis using the finite element method (FEM) is necessary to accomplish this because it can evaluate the distribution of the electromagnetic force produced in the magnetic circuit in detail.
This Application Note presents an evaluation of the torque waveform of a coreless motor when current is running.
40 - Cogging Torque Analysis of an SPM Motor40 - Cogging Torque Analysis of an SPM Motor
Module:DP2013-10-28
The rotor's rotation in a permanent magnet motor can generate positive and negative torque, even when there is no current flow. This torque is called "cogging torque." While output torque a center of focus in motors used in precision equipment, cogging torque reduction must be taken into account as well. Skew and fractional slots are means of reducing this cogging torque. Skew is a widely used technique that attempts to cancel out cogging torque by applying an appropriate amount of twist to the stator or rotor. This generates electromagnetic force in the thrust direction, however, which presents challenges such as a decrease in performance and an increase in manufacturing cost. Fractional slots do not have the drawbacks found in skew, but the winding pattern is different from that found with integer slots. This means that the torque generation becomes difficult to evaluate because the teeth geometry and the magnet's magnetization distribution are hard to design accurately.
In order to carry out these evaluations, an electromagnetic field analysis using the finite element method (FEM) needs to be carried out because it can perform detailed evaluations of the electromagnetic force distribution produced in the magnetic circuit.
This Application Note presents the use of magnetic field analysis to obtain the cogging torque of an 8-pole, 9-slot SPM motor, which has relatively small period.
39 - Torque Analysis of a Three Phase Induction Motor Accounting for the Skew39 - Torque Analysis of a Three Phase Induction Motor Accounting for the Skew
Module:DP,TR2012-07-31
An induction motor can utilize skew easily because the cage is constructed by metallic casting such as die casting. When skew is applied, it arranges the variations in the magnetic flux that links to the cage in a sinusoidal wave. This makes it possible to eliminate the harmonic components from the induction current that cause negative torque and contain things like the torque variations caused by influence from the slots.
Applying skew generally affects the flow of magnetic flux in the axial direction, making it complex. This is why an analysis that can correctly verify the three dimensional magnetic flux flow is necessary to obtain an advance evaluation of the skew's effects.
This Application Note presents a comparison of the torque waveforms of three phase squirrel cage induction motors with and without torque, and introduces the effects of using skew to reduce torque variations. Changes in the higher components caused by skew are also displayed by separating the frequencies of the secondary current, which causes the torque variations.
38 - Starting Performance Analysis of a Single Phase Induction Motor38 - Starting Performance Analysis of a Single Phase Induction Motor
Module:DP2013-02-28
Single phase induction motors are widely used as small output motors for the drives in household electrical appliances and office machinery, like fans and washing machines, because they can use single phase AC, the typical power source for home electronics. Unlike three phase AC, however, single phase AC cannot create a rotating magnetic field by itself, meaning that it cannot start a motor. For this reason, it needs to use an alternate method to generate a rotating magnetic field to start the motor.
It is important to verify whether or not torque is generated in the intended direction and continues to rotate stably ahead of time in the design phase. In order to carry out this verification, the conditions where the rotor follows the equation of motion according to the electromagnetic force mechanism and starts up need to be analyzed correctly.
The purpose of this Application Note is to introduce an example of a single phase induction motor that uses a capacitor to set up an auxiliary winding and show its rotation speed versus time, torque versus time, and the magnetic flux density distribution and current density distribution in the bar just after the motor starts.
36 - Operating Time Analysis of an Electromagnetic Relay36 - Operating Time Analysis of an Electromagnetic Relay
Module:TR2013-01-28
Electromagnetic relays are devices that use an electromagnet to physically connect and disconnect contact points. Magnetic flux is generated from the magnetomotive force, which is expressed as the product of the number of turns in the coil and the current that is applied to the coil. This flux produces an attraction force in the movable core, making the relay close.
To put it simply, the attractive force is determined from the area of the gap between the movable core and the stator core and the size of the magnetic flux density produced in said gap. With a relay whose movable core does not move linearly, however, it is hard to predict the magnetic flux density in the gap because it does not become parallel. The nonlinear magnetic properties of the iron core and yoke also affect the magnetic flux density in the gap. With a JMAG magnetic field analysis, it is possible to obtain the attraction force of the movable core while accounting for these factors.
This Application Note presents the use of the motion equation function to evaluate the operating time of an electromagnetic relay that uses a DC voltage drive.
28 - Magnetic Field Analysis of a Speed Sensor28 - Magnetic Field Analysis of a Speed Sensor
Module:TR2013-10-28
Antilock brake systems (ABS) have become a standard feature in vehicles, so speed sensors are attached to each wheel in order to measure their respective speeds. There are several methods of detecting rotation speed, but magnetic sensors are weather resistant and have a small number of parts because there only needs to be a gear on the rotation side, so they are widely used.
The challenges from a design standpoint are the angle and relative distance between the gear's teeth and sensor, and how to ensure sensitivity and responsiveness when considering the magnetic influence of the surrounding air. In order to proceed with an advance study like this that considers a precise geometry and material properties, an electromagnetic field analysis using the finite element method (FEM) is effective.
This Application Note presents the use of magnetic field analysis to evaluate the variation of the voltage signal of a magnetic speed sensor for a range of air gap distances.
25 - Analysis of a Claw Pole Alternator25 - Analysis of a Claw Pole Alternator
Module:TR2013-01-28
Demand for high fuel efficiency in vehicles has been growing every year, and auxiliary machines like power steering and coolant pumps have been switching to electrical operation to support those needs. This is why the amount of electrical power being used in typical gasoline vehicles is increasing with each passing year, and manufacturers are looking for high-output alternators that can supply this level of electricity. They need to increase the output density, however, because they cannot increase the size of the actuator to correspond with the added generation capacity. They also need to achieve higher efficiency.
A claw pole alternator generates electricity in the coil on the stator side with the rotor side acting as an electromagnet. The excitation coil on the rotor side is a single phase, and the claw pole is arranged so that it wraps around this coil. The claws that extend from the inside of the coil and the ones that extend from the outside of the coil have poles with different polar characteristics, and they have the same polar structure as a magnet that is arranged with magnetization that alternates between North and South. Because the alternator needs to be designed with a 3D geometry to account for the claw poles and the analysis needs to consider eddy currents generated in the surface of the claw poles, which are made from a metal plate, an electromagnetic field analysis using the finite element method would be the most useful, as it can simulate detailed geometries and account for eddy currents.
This Application Note presents the use of an electromagnetic field analysis to evaluate the output capacity of a claw pole alternator operating at 1500 rpm while accounting for eddy currents in the rotor core.
24 - Cogging Torque Analysis of an SPM Motor with a Skewed Stator24 - Cogging Torque Analysis of an SPM Motor with a Skewed Stator
Module:TR2013-06-27
Reductions in vibration and noise are being sought after because they are a cause of torque variations in motors, and demands for reduction are particularly strong with motors that are used in machine tools and power steering. Cogging torque, which is a torque variation that is produced when there is no current, is generated because the electromagnetic force, which is produced in the gap, changes in relation to the rotor's rotation, making it necessary to apply skew to the stator and rotor and improvise with the magnet and stator's geometry in order to limit said variations in electromagnetic force as a countermeasure for reducing the torque variations. When applying skew, force in the thrust direction is produced in exchange for a reduction in the cogging torque, meaning that there is the disadvantage of producing eddy currents from the magnetic flux that links in the lamination direction.
Consequently, in order to accurately evaluate a motor that has skew applied, one needs a magnetic field analysis simulation that uses the finite element method (FEM), which can account for a detailed 3D geometry, instead of studies that use the magnetic circuit method or a 2D magnetic field analysis.
This note presents the use of magnetic field analysis to evaluate the cogging torque of an SPM motor with a skewed stator.
23 - Eccentricity Analysis of an IPM Motor23 - Eccentricity Analysis of an IPM Motor
Module:DP2013-09-03
Rotor eccentricity is one cause of vibration and noise in motors. It is well known that motor torque is produced by electromagnetic attraction and repulsion between the stator and rotor, but not much attention is paid to the fact that electromagnetic attraction acts in the radial direction between the rotor and stator. This is because it seems that this electromagnetic force is canceled out and therefore not produced because the rotor and stator are normally arranged concentrically. However, if there are dimensional errors in the parts that support the shaft or stator and concentricity is not maintained, in other words if there is eccentricity, the electromagnetic force in the radial direction is not canceled out. In this case, friction increases due to the constant action of the radial load on the shaft bearings, causing vibration and noise.
A certain amount of error from processing has to be expected. Processing error itself is not so large that the parts cannot be put together, but even assembly error can cause a minute eccentricity of around 1/10 mm. Analysis that can handle this level of precision is needed to evaluate this kind of minute geometry difference, and electromagnetic field analysis using the Finite Element Method (FEM) is useful because it has the sensitivity for detailed geometry differences.
This Application Note presents how to obtain variations in electromagnetic force according to changes in the amount of rotor eccentricity.
16 - Analysis of a Hybrid Stepper Motor16 - Analysis of a Hybrid Stepper Motor
Module:TR2013-01-28
Hybrid stepper motors are used as actuators for equipment where position detection accuracy is required, such as the joints of robots or rotary tables for machine tools. The rotor has a construction that sandwiches a magnet that is magnetized in the axial direction between two rotor cores that have serrated teeth to create salient poles, and the tips of the stator core's teeth are shaped like gears as well. The rotation resolution is determined by the number of gears in the rotor and the number of phases in the drive coil, so the number of gears is set to rather large numbers like 50 and 100 to raise the angle resolution. The most important characteristics for a stepper motor are the controllability, the detent torque, which is a non-excitation holding torque, and the stiffness torque, which is an excitation holding torque, and not the motor's output.
The two-plated rotor core of a stepper motor has an N pole on one side and an S pole on the other, so a multipole magnet is achieved by deviating the saliency of the gear condition by 1/2 pitch. Consequently, the magnetic circuit is 3D. There are also times when the division pitch geometry of the teeth is complicated, so it is necessary to carry out a 3D electromagnetic field analysis using the finite element method (FEM) to proceed with an accurate preliminary study.
This Application Note describes how the detent torque and stiffness torque can be calculated for a hybrid stepper motor.
15 - Cogging Torque Analysis of  an SPM Motor with a Step Skewed Magnet15 - Cogging Torque Analysis of an SPM Motor with a Step Skewed Magnet
Module:TR2013-01-28
Reductions in vibration and noise are being sought after because they are a cause of torque variations in motors, and demands for reduction are particularly strong with motors that are used in machine tools and power steering. Cogging torque, which is a torque variation that is produced when there is no current, is generated because the electromagnetic force, which is produced in the gap, changes in relation to the rotor's rotation, making it necessary to apply skew to the stator and rotor and improvise with the magnet and stator's geometry in order to limit said variations in electromagnetic force as a countermeasure for reducing the torque variations. When applying skew, force in the thrust direction is produced in exchange for a reduction in the cogging torque, meaning that there is the disadvantage of producing eddy currents from the magnetic flux that links in the lamination direction.
Consequently, in order to accurately evaluate a motor that has skew applied, one needs a magnetic field analysis simulation that uses the finite element method (FEM), which can account for a detailed 3D geometry, instead of studies that use the magnetic circuit method or a 2D magnetic field analysis.
This Application Note presents the use of magnetic field analysis to evaluate the magnetic flux density distribution and cogging torque in each part of an SPM motor with a step skewed magnet.
6 - Analysis of the SR Motor Torque Ripple 6 - Analysis of the SR Motor Torque Ripple Module:DP 2012-04-10
With the skyrocketing prices of rare earth magnets, expectations have been rising for SR (switched reluctance) motors because they have a motor format that does not use permanent magnets. SR motors have a simple structure that can achieve solid performance at a low price. However, torque generation depends only upon the saliency between the stator and rotor, so torque variations are extremely large and cause vibration and noise, meaning that the use applications are limited. On the other hand, because of the skyrocketing prices of rare earth metals, the improvement in current control technology, the possibility of optimized designs thanks to magnetic field analysis, and the rising ability to reduce challenges, SR motors are being reexamined.
SR motors operate using the nonlinear region of a magnetic steel sheet, so the inductance displays nonlinear behavior that distorts the excitation current waveform a great deal, making it impossible to carry out advanced projections that are accurate with calculation methods that follow linear formulas. Consequently, it becomes necessary to use the finite element method (FEM), which can handle nonlinear magnetic properties in material and minute geometry as well as transient currents.
This Application Note explains how to carry out a torque analysis that changes the switch conversion timing and evaluate both the torque ripples and average torque in an SR motor.
2 - Cogging Analysis of a PM Linear Motor2 - Cogging Torque Analysis of a PM Linear Motor
Module:TR2013-01-28
Linear motors have been widely used in carrier devices and the drive units of machine tools due to their capability for high acceleration and deceleration, as well as their accurate positioning. As an issue for improving performance, people are trying to obtain a large thrust force in order to enhance responsiveness, but on the other hand it is also necessary to fulfill the demand for the trade-off of wanting to reduce thrust force variations and the attraction force.
In order to obtain a large thrust force, the material's nonlinear magnetic properties and the magnet's demagnetization characteristics need to be accounted for, and in order to evaluate thrust force variations, they need to be analyzed after modeling a detailed geometry. This is why they need to be studied with a magnetic field analysis simulation based on the finite element method (FEM).
This note presents how to obtain cogging, a cause of thrust variation, and evaluate the thrust force and attraction force during drive.

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