Emag AT Motor Definition allows you to create a file that defines an Electric Motor (both Electromagnetic excitation and Rotor and Stator structures). You can define an Electromagnetic excitation by referencing pre-calculated magnetic field data from 3rd party software. The structures are defined by FE Nastran models for Rotor and Stator. Figure 6 shows how to access the tools you need to define your electric motor.

The Emag AT Electric Motor Definition has the following tabs to help you design an electromotor.

 

To define an electro motor enter basic parameters in the General tab. See Figure 7.

 

The value defines the true width of the stator structure as the stator is usually part of housing or another belonging structure. See Figure 8.

The value defines the inner diameter of stator structure, resp diameter of surface formed by stator teeth tips. See Figure 9

The value defined angle spanning over stator tooth tip. See Figure 10.

The value defines in how much poles is the rotor divided. For pole definition see Figure 11.

The value defines in how many segments a rotor is divided along the width. See Figure 12.

The value defines the true width of rotor structure as the rotor is usually part of shaft or another belonging structure. See Figure 13.

The value defines the outer diameter of rotor structure which forms the air gap between rotor and stator. See Figure 13.

The value defines the axial shift between rotor and stator. In this release the parameter is not supported, so always zero offset is expected.

To calculate FE Grid force out of the magnetic force density, one needs to calculate surface of FE element belonging to the particular FE grid and multiply it with force density above this surface.There are three methods available for calculating the force density above the FE element. Two of them are based on middle value calculation above surface of FE element and one on local value interpolation on FE grid position. The middle value can be calculated with simple average method, see Equation (1) or more advance using Integration, see Equation (2).

This option either holds the rotor in the same position during force preprocessing, or enables rotation within one pole angle during the force preprocessing.

This setting influences how the resulting force on rotor pack is axially distributed to the FE grids.In Figure 14 i.e. for 3 FE elements per rotor pack the symmetric option evenly distributes the force over the 4 grids, while the shared grid between packs takes same amount of force from both adjacent packs, in contrast for unsymmetrical option the shared grid takes force only from pack 2, while there is no force contribution from pack 1.

This option influences how the forces are calculated on stator tooth FE grids. In Figure 15 there are 3 FE grids per tooth, in case no gap is considered the first and last tooth FE grid force contribution is limited on half of the FE element surface, hence also, half the force density acting on this area. In case tooth gap is considered, the gap is split into 2 half and the first and last tooth FE grids share also load acting over the gap surface.

The excitation by magnetic force acting on rotor and stator is defined on this card, see Figure 16.

Here the pre-calculated datasets coming from magnetic simulation are referenced for each Motor Operation Quadrant, see Figure 17.

Each quadrant is further described with a set of operation points for given rotor torque demand and rotor RPM. Each operating point is a table of amplitudes and phases defining Fourier series for each spatial coordinate δ on magnetic data mesh and for each rotor package, see Figure 18.

The Fourier series for each spatial coordinate describes a function of magnetic force density in respect to Rotor Angle is given by:

where, is the i-th Amplitude at δ position

is th i-th phase at δ position

is the i-th Motor Order

i is from 0 to Max_Order.

In the Magnetic force preprocessing, the continuous Fourier series for each spatial coordinate is discretized into n_rotational steps within one pole angle. The discretization allows to pre-calculate for each stator and rotor surface grid a discrete tangential and radial magnetic force as function of rotor rotational speed, rotor angle and torque demand.

 

The pre-calculated results from magnetic simulation are stored in time domain. This data is transformed into frequency domain using FFT, as a result the signal is decomposed in n-order, without any limitation. During the magnetic force preprocessing the max order taken into force density evaluation can be limited by this parameter.

Path to operation quadrants, the path can be browsed or copy pasted to the corresponding field. Files in corresponding folder and with defined extension are automatically referenced in the property file EMP and used for magnetic force preprocessing.

The structure of stator part is defined in this tab, see Figure 19. The data entered in this tab are used for definition of Nastran FE model for flexible body representation of housing and stator component. Those are later used in Adams model. Data from this tab is also used during magnetic force pre-calculation in order to prepare force for each FE grid on stator surface forming the air gap between rotor and stator.

 

The stator resp. stator and housing structure is represented by provided Nastran models. The Stator and Housing assembly model can by represented either as separate stator part and corresponding housing part, or as a full model of housing including stator. In case of two separated FE structures are used, the Connect. Type has to be set to GLUE option. If a full model is provided the field BDF Stator Packet has to be used and Connect. Type has to be set to NONE.

The local coordinate system of stator part is defined by Nastran coordinate system convention, The cylindrical system is defined by three points, see Figure 20.

It is important to define the coordinate system on rotational axis and in stator width half. The Z axis orientation should be set as follows; the rotation with positive sense about this axis should belong to Drive CCW quadrant of Motor operation. The X axis should point to one of the teeth center grids and indicates the pole start resp, the orientation of X axis of Magnetic force calculation system. This coordinate system is used for FE grids detection belonging to Stator surface forming the air gap and at the same time as coordinate system for modal shapes extracted by MNF generation.

For stator structure the FE mesh resp. surface forming the air gap is described by number of elements on tooth tip and number of elements in axial direction along full stator length, see Figure 21, since in contrast to rotor, there are no discrete packages defined on stator. Ideally the total number of elements on stator along axial direction is a multiple of rotor packages, so there is always the same number of elements corresponding to one rotor package.

The residual vectors are present in form of radial load defined on stator surface forming motor air gap, they are equidistantly distributed over stator circumference and width. Setting value to 0 deactivates residual vectors, setting to 1 creates n_poles * (n_packs+1) residual vectors, setting to 2 creates 2*n_poles * (2*n_packs+1) residual vectors and so on. The residual vectors together with the lower number of fixed boundary normal modes defined by Number of Modes parameter should form smaller but equivalent modal base as compared to complete but large modal base extracted if defined by Max Frequency parameter.

The structure of rotor part is defined in this tab, see Figure 22. The data entered in this tab are used for definition of Nastran FE model for flexible body representation of shaft and rotor component. Those are later used in Adams model. Data from this tab is also used during magnetic force pre-calculation in order to prepare force for each FE grid on rotor surface forming the air gap between rotor and stator.

 

The rotor resp. rotor and shaft assembly is represented by provided Nastran models. The rotor and shaft assembly model can by represented either as separate rotor part and corresponding shaft part, or as a full model of shaft including rotor. In the case of two separated models the Connect. Type has to be selected to GLUE. If a full model is provided the field BDF Stator Packet has to be used and Connect. Type has to be set to NONE.

The local coordinate system of rotor part is defined by Nastran coordinate system convention, The cylindrical system is defined by three points, see Figure 23.

It is important to define the coordinate system on rotational axis and in rotor width half. The Z axis orientation should be set as follows; the rotation with positive sense about this axis should belong to Drive CCW quadrant of Motor operation. The X axis should point to one of the rotor outer surface grids and indicates the pole start resp, the orientation of X axis of Magnetic force calculation system. This coordinate system is used for FE grids detection belonging to rotor surface forming the air gap and at the same time as coordinate system for modal shapes extracted by MNF generation

For rotor structure the FE mesh resp. surface forming the air gap is described by number of elements on rotor pole and number of elements in axial direction along rotor pack width, see Figure 24.

The residual vectors are present in form of radial load defined on rotor surface forming motor air gap, they are equidistantly distributed over rotor circumference and width. Setting value to 0 deactivates residual vectors, setting to 1 creates n_poles * (n_packs+1) residual vectors, setting to 2 creates 2*n_poles * (2*n_packs+1) residual vectors and so on. The residual vectors together with the lower number of fixed boundary normal modes defined by Number of Modes parameter should form smaller but equivalent modal base as compared to complete but large modal base extracted if defined by Max Frequency parameter.