Traditionally, motor control design and design of the motor itself have mostly been performed independently, and cooperative designs have been difficult to carry out. Also, for advanced motor control design, a motor model showing more details and conformity to the behavior of the actual machine is required by control simulation. In JMAG, it is possible to create a detailed model that conforms to the actual machine as well as account for spatial harmonics and magnetic saturation characteristics that are included in the motor. Importing this JMAG-RT motor model to a control/circuit simulator makes it possible to perform a linked simulation that accounts for a motor’s magnetic saturation and spatial harmonics as well as a motor drive’s control characteristics. Additionally, if the motor has a delta connection, cyclic currents will flow. This leads to an increase in copper loss and torque ripple, so it is beneficial to monitor cyclic currents while the motor is activated and feed back that information to control design and motor design.
In this example, the control and circuit simulator have been incorporated as a JMAG-RT model, and the cyclic current the IPM motor.is monitored.
The control circuit is shown in Fig. 1. The command values are 1800 r/min for rotation speed and 0 A for the d-axis current, and the voltage command value is connected to the motor via the inverter.
Rotation Speed Waveform, d-Axis Current Waveform
Fig. 2 shows the rotation speed waveform and Fig. 3 shows the d-axis current waveform. It can be seen that both become steady at their command values.
Fig. 4 shows the line current waveform at steady state, Fig. 5 shows the phase current waveform, and Fig. 6 shows the cyclic current waveform.
For motors that have a delta connection, cyclic currents flow due to an imbalance of back electromotive force which can cause copper loss and torque ripple. In this example, a cyclic current flows that is about half of the line current and phase current, and indicates that its contribution to loss is large.