Electricity: motive power systems – Switched reluctance motor commutation control
Patent
1988-08-31
1990-05-22
Smith, Jr., David
Electricity: motive power systems
Switched reluctance motor commutation control
318138, 318439, H02K 2900
Patent
active
049280422
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a circuit arrangement for operating a multi-phase synchronous motor on a direct current (d.c.) voltage mains, the synchronous motor having a number n of phases of its armature winding, and the arrangement including the number n of current valves connected respectively in series with the phases of the armature winding to the d.c. voltage mains, a ring counter having a counting input and the number n of parallel counting outputs each connected to the control input of an assigned current valve to drive successively the current valves into conduction during phase angle ranges which are approximately equal to 360.degree.
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In a known circuit arrangement of this type (German Offenlengungsschrift 3,042,819), the alternating voltages induced in the phases of the armature winding which are not connected are measured by the ring counter switching device and the ring counter is advanced and a phase of the armature winding is thus connected by actuating the corresponding current valve approximately symmetrically with respect to the crest of the negative half wave of the induced alternating voltage. The times for advancing the ring counter and thus for connecting or disconnecting the individual winding phases of the armature winding are determined by comparing the voltages induced in the winding phases not connected. For this purpose, the ring counter switching device exhibits, in a synchronous motor having an n-phase armature winding, n being an even number, an edge-triggered monostable flipflop which, following a trigger signal, generates at its input a counting pulse for the ring counter, and a comparison circuit which generates a trigger signal for the monostable flipflop whenever the voltage at the blocked armature winding which is offset by half an electric period with respect to the armature windings for which current flows, exceeds the voltages across the armature winding which directly lags or cyclically follows this armature winding. Due to the stepping on of the ring counter, this blocks again the momentarily opened current valve and opens a next current valve as a result of which in each case one phase of the armature winding is disconnected and the next following phase is connected. As has been mentioned, the respective winding phase is connected approximately symmetrically with respect to the crest of the negative half wave of the alternating voltage induced in the respective winding phase so that in a for example four-phase synchronous motor having the four voltages U.sub.1, U.sub.2, U.sub.3 and U.sub.4 dropped across the blocked current valves, the first current valve opens for as long as U.sub.3 is greater than U.sub.2 and greater than U.sub.4, the second current valve is conductive for as long as U.sub.4 is greater than U.sub.3 and greater than U.sub.1, the third current valve is conductive for as long as U.sub.1 is greater than U.sub.4 and greater than U.sub.2 and, finally, the fourth current valve opens for as long as U.sub.2 is greater than U.sub.1 and greater than U.sub.3. The connecting conditions of the current valves, that is to say U.sub.1 greater than U.sub.4 or U.sub.2 greater than U.sub.1 or U.sub.3 greater than U.sub.2 or U.sub.4 greater than U.sub.3 for one of the four current valves in each case exists in this arrangement over an electrical phase angle of 180.degree. which means that the switch-over condition occurs after 90.degree. of forward or 90.degree. of reverse rotation in each case. As a result, the motor can also start against the required direction of rotation and, although with reduced torque, without electric braking effect, after being correspondingly excited, for example due to a disadvantageous starting position or after the direction of rotation has been switched over.
Since no information on its position exists when the rotor or armature is standing still, an auxiliary pulse generator is provided in the known circuit arrangement. This auxiliary pulse generator starts the ring counter for starting up the motor and advances it in very
REFERENCES:
patent: 3931562 (1976-01-01), Visscher
patent: 4162435 (1979-07-01), Wright
patent: 4262237 (1981-04-01), Glenius
patent: 4431953 (1984-02-01), Schray et al.
patent: 4446406 (1984-05-01), Uzuka
Harms Klaus
Schray Hans-Dieter
Taubitz Bernd
Wirtz Rainer
Robert & Bosch GmbH
Smith Jr. David
Striker Michael J.
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