PMLSM force and back-EMF constant

PMLSM block's description defines an equality of force and back-EMF constants. But such equality is correct for single phase of linear motor only, isn't it? In this case, catalogue force and back-EMF constants must be reduced to single phase ones.

Answer 1

[Sabin]

The back EMF constant is the peak voltage induced by the permanent magnet in the per-unit rotational speed of each of the phases. The force constant is the peak force induced by the per-unit current of each of the phases. It is numerically identical in value to the back EMF constant when both are expressed in SI units.

[LeGa]

Or more simply: force and back-EMF constants are equal for single phase of rotary or linear motors in SI units. Thus, catalogue motor's data must be reduced to single phase. Must be noted that such constants are presented by different units (peak, RMS, 0-peak, peak-to-peak) with different manufacturers.

Answer 2

[Yahav]

I understand that the definitions of the motor constants are:

Force constant: N/Apeak , BEMF constant: (Vphase peak)/(m/s)

I recommend adding this to the block help.

The block should yield the same results, regardless if using Force constant (Kf), BEMf constant (Kv), or Flux linkage constant (PM). However, this is not the case in the example model: "Three-Phase PMLSM Drive". The PMLSM block has force constant: 0.18 N/A, BEMF constant: 0.18 V/(m/s), and Flux linkage constant: 0.65 Wb. The model tuned to use the PM constant, but when switching to Kf or Kv, it yields different results and its not following the ref profile. Kfand Kv yields same results, but not equal PM

Attached is a modified model which includes a BEMF test at imposed speed. both Kf and Kv yields good results, but not the PM.

[LeGa]

As I wrote hereabove, the force and back-EMF constants are presented with different units (peak, RMS, 0-peak, peak-to-peak) with different rotary/linear motor manufacturers. For set ones we must reduce ones to N/Apeak and (Vphase peak)/(m/s) respectively. The Parker/Trilogy AN Motor Parameters from Jack Marsh can help to do that.