Electric Motors

IPM motor: System level simulation

Interior permanent magnet synchronous motor (IPM motor) is a motor that is highly efficient and has a wide operation range, wherein this motor uses a rare earth-sintered permanent magnet having a strong magnetic force and uses a reluctance torque that is caused by the inductance difference of d- and q-axes, in addition to a magnet torque due to the magnetic field and the rotating magnetic field of the magnet.

Conventionally, most of the control design and the equipment design of a motor adopt a process of independently designing the components, and one of the technical challenges adopting such process is that it is difficult to coordinate the design aiming for optimization of the entire system.

However, this challenge can be solved by a coupled analysis of an electromagnetic field analysis tool ANSYS Maxwell and a control circuit system simulator ANSYS Simplorer, product of ANSYS. There are two major types of techniques that connects an electromagnetic field analysis and a circuit analysis, that is, a cosimulation that transiently carries out a direct coupling and a model-based simulation that handles an equivalent model (behavioral model) generated by an electromagnetic field analysis as one unit within the circuit analysis; however, with ANSYS Maxwell and ANSYS Simplorer, it is possible to perform a simulation at a system level with either technique in response to the user’s need.

With either technique, it is possible to perform a coupled simulation of control that takes into account the space harmonic and the magnetic saturation characteristics that the motor has. The cosimulation can take into consideration the loss phenomena such as core loss phenomena, and so on, with high precision, while the model-based simulation has a feature capable of a very high-speed control simulation.

Maxwell and Simplorer are both products developed by ANSYS, and the products have strengths including a support system and compatibility of tool coordination for a coupled analysis compared to the solution combining tools created by other companies.

Axial gap motor

Relevant product: >ANSYS Maxwell >ANSYS Simplorer

ANSYS Maxwell ＋ ANSYS Simplorer

Current waveform

Torque waveform

ANSYS Simplorer (ideal motor model) 

Current waveform

Torque waveform

Current tracking-type PWM drive of IPM motor 

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Direct-coupling transient analysis (cosimulation)

Current vector control drive of IPM motor 

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Direct-coupling transient analysis (cosimulation)

Motor rotational speed

Current waveform

Torque waveform

IPM motor: Inductance analysis

Interior permanent magnet synchronous motor (IPM motor) is a motor that is highly efficient and has a wide operation range, wherein this motor uses a rare earth-sintered permanent magnet having a strong magnetic force and uses a reluctance torque that is caused by the inductance difference of d- and q-axes, in addition to a magnet torque due to the magnetic field and the rotating magnetic field of the magnet.

IPM motor has an advantage in that a generated torque can be improved by using a reluctance torque by the saliency the rotor has, at the same time as a magnet torque, and in order to evaluate this saliency, it is important to grasp the inductance characteristics in the d- and q-axes at the design stage.

ANSYS Maxwell motor analysis can also calculate the inductance value of the transient response that is difficult by the inductance measurement from an induced electromotive force generally performed. The calculations of the three-phase inductance and the d- and q-axis inductance can be performed only by a simple operation using a standard function. 

IPM motor

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Transient response of IPM motor / three-phase inductance

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Transient response of IPM motor / d- and q-axis inductance

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Current characteristics of IPM motor / inductance

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IPM motor / Ld, Lq map

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IPM motor / Ld map

IPM motor / Lq map

IPM motor: Basic characteristic evaluation 

Interior permanent magnet synchronous motor (IPM motor) is a motor that is highly efficient and has a wide operation range, wherein this motor uses a rare earth-sintered permanent magnet having a strong magnetic force and uses a reluctance torque that is caused by the inductance difference of d- and q-axes, in addition to a magnet torque due to the magnetic field and the rotating magnetic field of the magnet.

IPM motor adopts a model in which a magnet is embedded inside a rotor and has been devised to be compatible with various rotor shapes. The shape needs to be selected to match with the target specification. An efficient motor design is possible by preparing a rough design using ANSYS RMxprt, specifying the shape, and then finalizing a detailed design using ANSYS Maxwell.

IPM motor model

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Example of motor model 

3D Model example using ANSYS Maxwell

Magnetic field display

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Iron loss distribution

Characteristic data

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Cogging torque

Torque and current phase angle

Interlinkage magnetic flux

Iron loss (time change display)

IPM motor: Eddy current of permanent magnet

Interior permanent magnet synchronous motor (IPM motor) is a motor that is highly efficient and has a wide operation range, wherein this motor uses a rare earth-sintered permanent magnet having a strong magnetic force and uses a reluctance torque that is caused by the inductance difference of d- and q-axes, in addition to a magnet torque due to the magnetic field and the rotating magnetic field of the magnet.

In a vector system that has a wide rotational speed region and uses a reluctance torque, a current including a carrier harmonic is entered into a coil. An eddy current loss is generated inside a magnet by a high long wave component [sic, harmonic component?].

Dividing the magnet is effective in minimizing this loss. The difference in eddy current loss by the division of magnet can be estimated by ANSYS Maxwell. 

IPM motor model

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Rotor 

Eddy current distribution

Analysis results

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Current vector display of the eddy current distribution

No magnet division

With magnet division

Setting of insulating boundary conditions on the division surface

Change in the magnet loss and the number of magnet divisions

IPM motor: Thermal demagnetization analysis

Interior permanent magnet synchronous motor (IPM motor) is a motor that is highly efficient and has a wide operation range, wherein this motor uses a rare earth-sintered permanent magnet having a strong magnetic force and uses a reluctance torque that is caused by the inductance difference of d- and q-axes, in addition to a magnet torque due to the magnetic field and the rotating magnetic field of the magnet.

Neodymium iron-type rare earth magnets that are often used in motors using these permanent magnets have, on the one hand, an excellent magnetic property that is called an interlinked magnetic flux density, but on the other hand, are known to be easily demagnetized at high temperatures.

The electromagnetic field design and the heat and structure design of a motor conventionally adopt a process of independently designing the components, and one of the technical challenges adopting such process is that it is difficult to coordinate the design aiming for optimization of the entire system. However, the challenge of this multiphysics simulation can be solved by a coupled analysis of an electromagnetic field analysis tool ANSYS Maxwell and a thermo-fluid analysis software ANSYS Fluent.

A design engineer can perform this analysis with ease by utilizing ANSYS Workbench platform to tackle this analysis challenge that has been a big hurdle in the past.
ANSYS Maxwell and ANSYS Fluent are both developed by ANSYS, so both products have strengths including a support system and compatibility of tool coordination for a coupled analysis compared to the solution combining tools created by other companies. 

Permanent magnet thermal demagnetization analysis of IPM motor (electromagnetic field - thermal fluid analysis) 

Related product: >ANSYS Maxwell >ANSYS Fluent

Permanent magnet demagnetization curve

A coupled analysis of Maxwell and Fluent can be performed with ease by ANSYS Workbench

Temperature distribution

Decreased torque due to thermal demagnetization

Permanent magnet thermal demagnetization analysis of IPM motor (Maxwell - Fluent) 

Loss distribution

Switched reluctance motor

In response to the rising prices of rare earth magnets, a switched reluctance motor (SR motor) has garnered expectations as a motor model that does not use a permanent magnet. An SR motor has a simple structure, is robust, and can be realized inexpensively; however, its usage application has been limited because of very large torque variations due to nonlinear saliency of the rotor and the stator in terms of the principle of the torque generation, and accompanied with vibrations and noise. However, the SR motor has been reviewed as the candidate that may solve such challenges in response to the soaring price of rare earth magnets, enabling an optimum design by a magnetic field analysis and the improvement of the current control technique.

SR motor may be driven by changing the switch timing depending on the rotational speed, so it is beneficial in grasping the characteristics including the torque, current, loss, and efficiency depending on the rotational speed.

Inverter drive analysis and torque ripple of SR motor

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Magnetic field distribution of SR motor 

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Magnetization characteristics and static characteristics of SR motor 

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Vibration and eigenvalue analysis of SR motor 

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SPM (Surface Permanent Magnet) motor

SPM motor is a synchronous motor of rotary field type that has a shape in which magnets are laminated on the surface of a rotating body (rotor). This is a motor optimum for control because it has linearity having a good relation between the torque and the current.

Furthermore, it has the optimal shape for a small motor with a small output; however, a magnetic analysis by a finite element method becomes necessary on variations in rotation including a cogging torque. With the demands of miniaturization and high output in recent years, the distribution of magnetic saturation needs to be precisely analyzed, so a magnetic analysis becomes an important technique

SPM motor model (2D/3D) 

Related product: >ANSYS Maxwell

Example of SPM motor model (2D model) 

Example of SPM motor model (3D model) 

Example of creating a drive circuit by ANSYS Maxwell Circuit Editor (Maxwell standard equipment) 

Magnetic field display

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Mag_B (Magnetic flux density distribution

B_Vector (Magnetic flux density vector distribution)

Mag_H (magnetic field intensity distribution)

Mag_B (Magnetic flux density distribution)

B_Vector (Magnetic flux density vector distribution)

Flux Line (Magnetic flux diagram)

Mag_H (magnetic field intensity distribution)

Jz (Z-direction current density distribution)

Characteristic data

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Cogging torque waveform

Analysis example by three-phase layer drive inverter of 120º energization method

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Coil current (three phases)

Switching pattern

Torque 

Loss

Three-phase induced voltage

SPM motor/cogging torque analysis

A motor that uses a permanent magnet that has an iron core can be designed as a high-output motor of a small size; however, there is a demerit of cogging torque, and so on.

A cogging torque is influenced by the torque pulsation, adversely affecting the stability of mechanical vibration, noise, and drive system and the reliability as a product.

However, the cogging torque is a sensitive torque, wherein an actual measurement is difficult, and a nonlinear element is strong, so it is very beneficial in designing the utilization of an electromagnetic field analysis capable of high-precision simulation.

ANSYS electromagnetic field analysis is an optimal analysis tool that can automatically generate an optimal mesh by adaptive auto meshing and be used in a sensitive characteristic analysis of a cogging torque, and so on.

SPM motor 

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Difference in magnetic flux density waveform due to the differences in the magnetization directions on the rotor surface of the motor

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Polar anisotropic magnet

Radial anisotropic magnet

Cogging torque waveform of SPM motor due to the difference in the magnetization direction

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Cogging Torque Waveform

Flux line

Effect on the torque ripple due to the difference in the magnetization direction

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Torque waveform of SPM motor 

At sinusoidal drive (current source drive)

At 120º energized inverter drive (voltage source drive) 

Three-phase induction motor

Induction motors have been utilized in the past in wide fields of application from industrial applications to household applications, wherein the motor is driven by flowing an induction current to a secondary conductor by the rotating magnetic field of a stator winding, and the rotor receiving the power in the rotational direction by its current and the rotating magnetic field. The motor has a simple structure and advantages of being small in size, light in weight, inexpensive and maintainable. 

In response to the soaring price of rare earth magnets seen in recent years, research and development have been active again for developing induction motors that are small in size and have high output and high efficiency, targeting the needs similar to those in a permanent magnet synchronous motor as a motor model that does not use a permanent magnet. High-precision characteristic evaluation and comprehension using an electromagnetic field analysis tool are beneficial in the design and development of such high-performance induction motors 

Current and torque ripple waveforms of three-phase induction motor

Related product: >ANSYS Maxwell

Current waveform of three-phase induction motor

Torque ripple waveform of three-phase induction motor

Magnetic field distribution of three-phase induction motor

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Magnetic flux density

Magnetic flux diagram

Current density distribution of car conductor part of the secondary side

Core iron loss distribution (time average)

Magnetic flux density vector

Speed – torque, output, efficiency, and power factor characteristics of a three-phase induction motor

Related product: >ANSYS RMxprt

Cooling design and thermal fluid analysis of a three-phase induction motor

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DC motor with brush

DC motor with a brush has windings, magnets, and commutators, can be easily driven by connecting a DC power supply, and has a proportional relationship between the torque and the current, thereby having high controllability. Based on such characteristics, the motor is used in various fields, and becomes one of the motors with the most production volume.

DC motor models with brush (2D/3D) 

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2D model

3D model

Example of creating a drive circuit by ANSYS Maxwell Circuit Editor (Maxwell standard equipment) 

Display of various fields

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Display of magnetic flux density

Display of magnetic field

Display of current density vector

Characteristic data

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Interlinkage magnetic flux

Induced voltage

Output and efficiency characteristic graph

T-I and T-N characteristic graph 

Linear synchronous motor

A linear motor is an electric device that provides an electromagnetic force by causing a direct and linear movement to a subject, and a structure in which a cylindrical rotary motor is developed linearly can be considered.

The linear motor has a long history similar to that of a rotating machine. In recent years, a direct drive becomes possible in which a thrust in any direction is given to the driven object without contact; and in addition to the characteristics of high speed, high resolution, high precision, and high reliability, the application of a linear motor to a positioning device is expanding by the improvement of repeating precision of positioning and freedom of movement by an integration with a servo control technology.

An analysis example in a coreless-type linear synchronous motor will be introduced here.

A coreless type refers to a type of motor that does not use iron including an electromagnetic steel sheet at the portion at which a coil is wound. This type of linear motor, in principle, does not have a cogging torque, so it is used in devices for performing positioning at higher precision. 

Analysis model

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Analysis model

Mover (three-phase coreless coil)

Display of various fields

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Magnetic flux density distribution

Magnetic flux density distribution (sectional)

Coil current

Distribution of force applied to the coil

Characteristic data - transient response at reciprocating motion

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Current waveform

Voltage waveform

Interlinked magnetic flux waveform

Position 

Speed 

VR-type resolver

A resolver is one of the rotation angle sensors often used in a motor, and the like. Although it is one kind of alternator, it is configured by a two-phase coil in which the winding direction of the output is orthogonal, wherein generated voltages of sinφ and cosφ are detected in proportion to the rotation angle to obtain a rotation angle as a digital value by an A/D converter, or the like. It has a simple configuration as compared with that of a rotary encoder, which makes it suitable to be used in adverse environments; however, it has disadvantages such as complicated signal processing circuit and inferior detection accuracy to the encoder.

By combining the electromagnetic field analysis and the circuit analysis of ANSYS, it is possible to perform a system simulation including not only the electromagnetic design of the resolver body but also the drive encoder and cables, allowing high-precision and optimal cooperative design of the whole system.

VR-type resolver

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Electromagnetic field analysis model of cable

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System simulation of a rotor position detection using an electromagnetic field analysis model of cable and resolver

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Doubly-fed induction generator (DFIG) 

This is an essential technical element to optimize power generation efficiency with respect to the wind speed that fluctuates from time to time during a variable speed operation in wind power generation using large wind turbines. A doubly-fed induction generator (DFIG) is generally adopted in a wind turbine generator using a large windmill.

By combining the electromagnetic field analysis and the circuit analysis of ANSYS, system simulation including an inverter not only for the electromagnetic design of a generator is possible, allowing high-precision and optimal cooperative design of the whole system.

DFIG

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Control system simulation for a system operation of a wind-power 
generation using an electromagnetic field analysis of DFIG 

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Synchronous reluctance motor (SynRM) 

In response to the soaring price of rare earth magnets, a synchronous reluctance motor (SynRM) has attracted attention as a type of motor that does not use a permanent magnet. SynRM is robust and has a simple structure and can be realized inexpensively. However, because the principle of torque generation is due to only a reluctance torque by the magnetizing force of the coil and the saliency of the rotor, in order to increase the torque density, it largely depends on the nonlinear magnetization characteristics and the shape structure of the core, and it is not the type of motor typically used up to date. However, SynRM has been reviewed as the candidate that can possibly reduce such problems in response to the soaring price of rare earth magnets, enabling an optimal design by magnetic field analysis and the improvement of the current control technique.

SynRM operates using a nonlinear region of an electromagnetic steel sheet, therefore showing a nonlinear behavior due to magnetic saturation not only with respect to the rotor position but also to the inductance. This also causes the current waveform to become easily distorted. However, it is impossible to obtain a precise prediction with high accuracy using a calculation method along a linear theory formula. An electromagnetic field analysis by a finite element method is beneficial because it can handle a transient current, detailed motor shapes, and nonlinear magnetization characteristics of materials.

Synchronous reluctance motor

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Transient response output waveform

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Current phase angle - torque characteristics of SynRM

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Changes in torque and saliency ratio from the improvement in the rotor shape of SynRM 

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Before Improvement
After Improvement

Single phase induction motor

Induction motors have been utilized in the past in wide fields of application from industrial applications to household applications, wherein the motor is driven by flowing an induction current to a secondary conductor by the rotating magnetic field of a stator winding, and the rotor receiving the power in the rotational direction by its current and the rotating magnetic field. It has advantages such as a simple structure, small in size, light in weight, inexpensive, and maintainable. 

A single phase induction motor is widely used in fans with small output, ceiling fans, and so on, because it can be easily driven by a single-phase AC power source for ordinary households.

Single phase induction motor

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Magnetic field distribution of a single-phase induction motor

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Magnetic flux density

Magnetic flux diagram

Current density distribution of car conductor part of the secondary side

Magnetic flux density vector

Speed – torque, output, efficiency, and power factor characteristics of a single-phase induction motor

Related product: >ANSYS RMxprt

Universal motor

A universal motor is a motor that can be operated irrespective of whether the power supply is a DC or AC, has a simple structure and robustness that enables a high-speed rotation. It is used in home appliances and industrial tools up to date.

Universal motor

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Magnetic field distribution of a universal motor

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Magnetic flux density and magnetic flux diagram

T-N and T-I of a universal motor

Related product: >ANSYS RMxprt

Speed – torque, output, efficiency, and power factor characteristics of a universal motor

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Salient-pole synchronous generator

Salient pole synchronous generator is often used in large generators in power plants. The power is generated by the electromagnetic induction of a stator coil by providing a field current to the coil of a rotor and rotating the rotor.

Because in a salient pole synchronous generator, any power factor can be obtained by adjusting the field current depending on the load and the power factor of the load connected, V-curve characteristics showing a relationship between the armature current and the field current are investigated.

Salient-pole synchronous generator

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Magnetic field analysis of a salient pole synchronous generator

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Magnetic flux density distribution (at load)

Induced voltage waveform (at no load)

V- curve characteristics of a synchronous generator

Related product: >ANSYS RMxprt

Claw-pole generator

A claw pole generator is used as an alternator in vehicles. Each rotor pole has a structure of overlapping claws, so it is called a claw pole. Generators of this claw pole type
 are increasingly utilized as motors for stators in recent years, and a magnetic analysis is used to analyze the shape for fulfilling the characteristics of both the generator and the motor.

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Example of model preparation by ANSYS Maxwell 3D

Cross section

Overall picture

Example of model preparation by ANSYS RMxprt

Magnetic field analysis of a salient pole synchronous generator

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Magnetic flux density distribution (at no load)

Characteristic waveform

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Induced voltage waveform (no load)

Axial gap motor

An axial gap motor is a motor that has a configuration in which the stator is located opposite to the rotor arranged in a disc shape. Therefore, this motor is suitable in small and thin size and at high torque. However, the magnetic flux is flowing in the axial direction, so a magnetic analysis by a 3D model is required for a precise design. 

Axial gap motor

Related product: >ANSYS RMxprt >ANSYS Maxwell

Example of model preparation by ANSYS Maxwell 3D

Overall picture

Example of model preparation by ANSYS RMxprt

Magnetic field analysis of a salient pole synchronous generator

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Magnetic flux density distribution (at no load)

Characteristic waveform

Related product: >ANSYS RMxprt

Torque 

Interlinkage magnetic flux density

Phase current

Electromagnetic field - vibration and noise analysis

In many electric devices, in addition to motors, the problems of vibration and noise caused by an electromagnetic force have challenged design engineers for a long time.

Conventionally, most of the electromagnetic field design and the structure design adopt a process of independently designing the components, and one of the technical challenges adopting such process is that it is difficult to coordinate the design aiming for optimization of the entire system. However, the challenge of this multiphysics simulation can be solved by a coupled analysis using an electromagnetic field analysis tool ANSYS Maxwell and a structural analysis software ANSYS Mechanical, product of ANSYS.

With the new function installed in the new version ANSYS R15.0, the electromagnetic force data of time response obtained from a transient response analysis (time response analysis) using the electromagnetic field analysis tool ANSYS Maxwell are subjected to FFT conversion and [the analysis] is continued to be performed until mapping to the frequency response analysis of the structural analysis. By utilizing a platform called ANSYS Workbench, a design engineer can perform this analysis with ease, even with respect to these analysis challenges that have become a hurdle in the past such as time response in the electromagnetic field and frequency response in the structure analysis.

Furthermore, by utilizing the ANSYS ACT Extension function, it is possible to analyze noises and the sound pressure field to the surroundings in the structure analysis.

ANSYS Maxwell and ANSYS Mechanical are both products developed by ANSYS, and the products have strengths including a support system and compatibility of tool coordination for a coupled analysis compared to the solution combining tools created by other companies.

ANSYS Workbench makes it possible for a coupled analysis using Maxwell and Mechanical with ease. 

Vibration and noise analysis of permanent magnet synchronous motor (electromagnetic field - structure analysis)

Related product: >ANSYS Maxwell >ANSYS Mechanical

	Magnetic field analysis		Vibration analysis	Acoustic analysis