Machine/drive circuit interactions in small variable-reluctancestepping and brushless DC motor systems
Acarnley, P.P.; Hughes, A.
Industrial Electronics, IEEE Transactions on
Volume 35, Issue 1, Feb 1988 Page(s):67 - 74
Digital Object Identifier 10.1109/41.3064
Summary:The authors investigate the torque, losses, and efficiency of
small brushless DC and stepping-motor systems, and explain how
performance is influenced by excitation mode, drive circuit, and machine
parameters. Quantitative deductions are made for a three-phase
reluctance-type machine based on computed steady-state results. For a
given machine and drive circuit, maximum torque is obtained with an
excitation mode that allows each phase to be turned on for half of the
complete excitation cycle. However, if maximum efficiency is the aim,
phase excitation must occur for a shorter period, e.g. by exciting only
one phase at a time. When making comparisons between drive circuits, the
most important measure of drive-circuit capability is the circuit power
available at low speeds. Drive circuits producing rapid current decay at
phase turn-off benefit torque production in the two-phase-on excitation
mode, but are detrimental with the one-phase-on mode. At high speed the
pull-out torque depends on the unsaturated inductance parameters of the
machine. For maximum torque these parameters must be correctly
proportioned, their values being dependent on the excitation mode
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