Sensorless PMS Motor Control: Part 2: Vector-Summed
Control
by Dennis L. Feucht
Innovatia Laboratories
The Y-configured series voltage at the terminal pairs of the motor is the
vector sum of two phase-windings, YZ (= Y Z) and lags Y by 30° el. Without
current, the open phase-winding has no voltage drop across its series impedance,
and the induced voltage can be sensed directly. Furthermore, the open phase
voltage is the sum of the voltage at the common (or neutral) node,
N, and the phase-winding's own vω. Sensing the open phase voltage
with respect to N results in a voltage in phase with the open phase vω.
Unfortunately, the easily-sensed open-phase zero-crossings occur in the
middle of phase-steps (30 offset) and cannot be used alone to advance phase.
The design goal for phase control is to maintain field orientation at the
midrange of a phase-step, so that peak error in δ is minimized to
±30° el around it.
...download complete Part II here 47kb PDF file)
...download complete Part I here (146kb DOC file)
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