Electricity: motive power systems – Reciprocating or oscillating motor – Energizing winding circuit control
Patent
1980-01-10
1983-06-07
Truhe, J. V.
Electricity: motive power systems
Reciprocating or oscillating motor
Energizing winding circuit control
318254, 318701, H02K 2902
Patent
active
043873260
DESCRIPTION:
BRIEF SUMMARY
This invention relates to variable reluctance motor systems and is concerned with circuits employing thyristors to connect a direct voltage (d.v) source sequentially to the windings of a variable reluctance motor.
According to the present invention a variable reluctance electric motor system includes a variable reluctance motor having a main winding for each of an even number of phases greater than two, and a power converter circuit including a main thyristor in series with each main winding of the motor so connected across one or more d.v. sources, from which the main windings are supplied sequentially with unidirectional current pulses, that the current in each main winding is independent of that in the other main windings, characterised in that of two successive phases (taken in their order of conduction) one has its phase winding connected to the positive terminal of a d.v. source and has a commutating thyristor which connects the junction of the main thyristor and main winding to a junction point of a capacity unit so as to starve the main thyristor of the current flowing from the positive source terminal through the winding, while charging the capacitor terminal positively, whereafter the commutating thyristor of the next phase, having its phase winding connected to the negative terminal of a d.v. source, connects the junction of its main thyristor and main winding to a junction point of the said capacitor unit so as to starve the main thyristor of the current flowing through the main winding to the negative source terminal while charging the capacitor terminal negatively, whereby a commutation of a main thyristor, initiated by firing a commutating thyristor and terminated when this commutating thyristor ceases to conduct, leaves the commutating capacitor or capacitors charged with the correct polarity and adequate voltage for the commutation of the next main thyristor in the conducting sequence.
Known commutating circuits, having performed their turn-off function for a particular thyristor, leave the commutating capacitor or capacitors charged with a polarity which is opposite to that required to turn-off the next thyristor in the sequence of thyristor conduction. An additional thyristor in series with an inductor is necessary forming a resetting circuit through which a half cycle of current flows whereby the polarity of the capacitors is reversed.
The present invention is concerned not only with the arrangement of the thyristors through which current flows from the d.v. source to the motor windings whereby the completion of one commutation leaves the commutating capacitor(s) with the correct polarity for the commutation of the next thyristor in the conducting sequence, but also with the requirement that the magnitude of the voltage left on the capacitor at the completion of one commutation is adequate for the commutation of the next thyristor in the conducting sequence.
The invention may conveniently be applied to variable reluctance motors having a main winding and a closely coupled auxiliary winding for each phase, or to such motors having a single winding for each phase in which case one end of every winding is connected together and connected to a mid-tapping on the d.v. source.
When the motor has main and auxiliary windings the phase current referred to hereafter is defined as the sum of the main winding current and m time the auxiliary winding current where m is the ratio of the auxiliary to main winding turns.
The present invention has the advantage that it avoids the need for a resetting circuit formed by an additional thyristor and inductor in series, and so eliminates the power losses associated with this circuit. The invention also halves the frequency of fundamental voltage across the commutating capacitor compared to the frequency necessary when a resetting circuit is used. The frequency reduction reduces capacitor losses. A third advantage of the invention is to reduce the voltage excursions across the commutating capacitor compared to those which occur when a resetting circuit is use
REFERENCES:
patent: 3262036 (1966-07-01), Clarke et al.
patent: 3401323 (1968-09-01), French
patent: 3560818 (1971-02-01), Amato
patent: 3639818 (1972-02-01), Wiart
patent: 3697840 (1972-10-01), Koch
patent: 3956678 (1976-05-01), Byrne et al.
patent: 4270075 (1981-05-01), Nygaard
Davis Rex M.
Ray William F.
Chloride Group Limited
Evans A.
Truhe J. V.
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