How to Use JMAG‐RT Models
Overview
JMAG-RT models are derived from JMAG finite element analysis (FEA) models. By running JMAG in advance under different operating conditions, results are stored in a JMAG-RT file. A JMAG-RT model retains the accuracy of an FEA model but is significantly faster than the FEA model since FEA simulation is no longer needed at the time of calculation.
PSIM provides the function to support all types of JMAG-RT models, including:
- PMSM (LdLq model, spatial harmonics model, and flux integral model)
- Solenoid
- Linear synchronous motor
- Wound field synchronous motor
- Step motor
- Switched reluctance motor (3, 4, and 5 phases)
- Induction motor
- Generic model
This tutorial will describe how to use JMAG-RT models in PSIM, and how to evaluate the performance of a motor drive system with JMAG-RT models.
Using JMAG-RT Models
To load a JMAG-RT model into PSIM, go to Elements >> Power >> MagCoupler-RT Module, and select RT Block (RT), as shown below:
Place the element in the schematic. Double click on it to open the parameter dialog, as shown below on the left.
The block will have a default image of a PMSM. But the image will change depending on the type of the JMAG-RT model loaded.
Click on the browser button (next to the “JMAG input file” input field), and select your JMAG-RT file, as shown in the above image on the right. A JMAG-RT file has the .rtt extension.
Define the RT Block parameters. For more information on the definitions of the parameters, please refer to the online help. Click on the Help button on the RT Block dialog. On the RT Block help page, click on the type of JMAG-RT model loaded (for example, for PMSM, click on the PMSM link), as shown below.
The RT Block is part of the MagCoupler-RT Module, an add-on Module to PSIM. One must have the MagCoupler-RT Module in the license.
Note that running simulation with JMAG-RT models in PSIM does not require JMAG to be installed, and does not require a JMAG license.
Motor Drive Performance Evaluation Using JMAG-RT Models
A JMAG-RT model can be used like any other built-in PSIM library element. In order to facilitate the performance evaluation of a motor drive system that uses a JMAG-RT model, two design templates are provided under the Motor Control Design Suite: PMSM (IPM) Drive (JMAG-RT) for IPM drive with speed control, and PMSM (IPM) Drive (JMAG-RT)(torque control) for IPM drive with torque control, as shown below.
To select one of the templates, go to Design Suites >> Motor Control Design Suite, and select the template from the list.
For more information on the Motor Control Design Suite, please refer to the document “Tutorial – Motor Control Design Suite.pdf”.
The PMSM (IPM) Drive (JMAG-RT) template for speed control is shown below.
On the left of the schematic is the Input Parameter Panel. Specify the system operating conditions, such as dc bus voltage, inverter current, load, motor parameters, and controller parameters. Then click on Update Parameter File, the Design Suite will design the current loop controller and speed loop controller automatically.
Under the Motor section of the Parameter Panel, inductances Ld and Lq correspond to the values at the desired operating conditions.
Click on the Speed-Torque Curve button to view the curves of speed vs. torque and power. This gives a quick overview of the boundary of the drive operation.
The simulation waveforms are shown in the upper right corner.
In the schematic, Inductances Ld and Lq, which are nonlinear and a function of the currents, are read from the JMAG-RT model and are used in the nonlinear motor control block. This saves users the trouble of preparing the Ld and Lq tables. The nonlinear motor control block incorporates advanced Maximum-Torque-Per-Ampere (MTPA) control, field weakening control, and Maximum-Torque-Per-Volt (MTPV) control to achieve the maximum drive performance in the full operation range, including the high-speed region.
Simulation waveforms on the right show the change of the Ld and Lq inductances, the copper loss, and the eddy current and hysteresis losses.
Since the JMAG-RT model is based on finite element analysis, all the nonlinear effects of the motor, such as saturation, spatial harmonics, cogging torque effect, dc and ac copper losses, and eddy current and hysteresis losses, are taken into account. With the Motor Control Design Suite, the performance of a realistic motor drive system can be quickly evaluated.
The PMSM (IPM) Drive (JMAG-RT)(torque control) template for torque control is shown below.
The torque control template is similar to the speed control block, except that the mechanical load is a constant-speed load, and the nonlinear control block is for torque control. A feedback torque control loop is included internally in the control block.
With the torque control template, one can generate the efficiency map of the entire motor drive system. The efficiency of the motor can be obtained from the JMAG-RT model. By replacing the 3-phase inverter with a Thermal Module 3-phase inverter, one can calculate the inverter efficiency. By doing a parameter sweep of the torque command and the rotor speed, we can obtain the efficiencies of the system, including both motor and inverter, at different speeds and torques.
Obtaining JMAG-RT Models from JMAG-Express Online
JMAG-Express Online is a free web-based online platform provided by JSOL Co. With the minimum inputs, one can design a motor quickly. Moreover, it can generate JMAG-RT models from the design for PSIM simulation.
Click on the JMAG-Express Online button. A web browser will be launched with the login page of JMAG-Express Online. Log in to your account (an account must be created in advance). Screenshots of the JMAG-Express Online pages are shown below (in the middle and on the right).
After a motor is designed in JMAG-Express Online, go to File >> Create JMAG-RT Model to create the model. After the model is created, go to File >> User Data, and select the JMAG-RT model file, and click on Download to download to the local drive, as shown below:
This JMAG-RT model file is now ready to be used for PSIM simulation.
Motor parameters needed for simulation can be manually read from JMAG-Express Online. Alternatively, PSIM provides an easier way to extract them. Click on the button Download Machine Data on the RT Block dialog. After some delay, a dialog will appear as below:
Save this file to a folder, and it will be loaded to a text editor. A sample motor parameter file for a PMSM motor is shown below:
J = 0.000918095; // moment of inertia
Rs = 0.006102; // phase resistance
Ld = 0.00099161; // Ld inductance
Lq = 0.00171796; // Lq inductance
Kt = 0.281355; // torque constant
Ke = 0.324881*(2*PI*1000)/60; // Vpk/krpm
Tb = 6.629; // base developed torque
Pb = 5051; // base power
It contains parameters such as resistance, Ld, Lq, back EMF constant Ke, and moment of inertia. Enter them into the Input Parameter Panel in the Motor Control Design Suite templates, or use them in the PSIM simulation.