Analytical Design Properties
Access this from the "Tools" menu.
This property page helps to set certain parameter for general use for all designs especially for slotted motors. Some other features include exclusion of the slot liner from the model generation and forcing the software to compute cogging torque, speed-torque curves with every change. These features can be turned on and off and will affect all subsequent designs.
The back emf can be smoothed by sampling in the slot, this option can be turned on and the number of points to sample can be specified. The method to use while computing the back emf can be set here.
The slot opening (Use So) can be optionally used while calculating the magnetic circuit and is only required in motors where the slot opening is large. If the slot opening is large, leakage paths are available for the magnet flux to return without interacting with the tooth or coils, so this option can be turned ON to effectively reduce the flux density in the teeth and back iron. It also reduces the amplitude of the back emf if the method of back emf calculation is via the tooth flux method. This option will be moved to the main input data properties in a future release. Please remember to manually change this value again when designing regular motors as this setting affects all designs.
Multiples of Lm which is the radial thickness of the magnet can be optionally added to the axial length of the effective magnet length to increase the magnet area to take fringing flux into account. It is recommended that this be set between 0.0 to 1.0 based on the way typical designs are made at your facility.
The magnet harmonic number specifies the number of harmonics to use if the "smooth bored" magnet waveform generation is used. The slot opening divisions specify the number of divisions that the slot opening is broken into during cogging torque calculations. The Fourier harmonics specifies how many harmonic values will be sent to the graph window.
The core loss check box allows you to compute core loss from the calculated values for flux density instead of the values obtained from the waveforms. This is usually not used this way.
The power input can be matched with the power output optionally. If this option is not checked, true torque can be obtained but the new speed that the motor will run at is not calculated. So, there will be a small error in the calculated efficiency and the actual rated speed. This option is automatically disabled while generating speed torque curves. Please note that this option does not generate accurate results at all time and the error may be very high especially during PWM action of the drive. This has been added at the insistence of certain users, please use with caution. Input power is calculated as the supply voltage times the supply current in all cases.
A second property page called Iterations (not shown) controls the different options available for simulation the phase currents in wye and delta connected motors. The method of computing inductance can be defined here. Samarium uses two independent set of equations to calculate the various inductances.
Slotted Motor Design Procedure
The type of motor and rotor is chosen first. Then the basic dimension parameters are set. The number of magnet poles, magnet material, stator, and hub steel materials are then set. The flux density values in the stator teeth, stator back iron, and rotor back iron are inspected and the dimensions adjusted so they are at acceptable values. The core loss at rated speed is also inspected and additional adjustments are made to the dimensions. Next the number of turns, the wire size, and the strands are adjusted so that the desired resistance and back emf are obtained. The slot fill factor is an important factor to be watched in this process. This procedure is repeated while changing parameters including materials until all desired objectives are obtained.
An important parameter to watch for initially is the air gap magnet flux density waveform. If this waveform is modeled incorrectly, all other related parameters will also contain errors.