US3703672A — Three-phase induction-motor, speed-changing metho…

Claim 1

Independent Claim 71 words

rA method of speed-changing for a three-phase induction motor supplied from a three-phase alternating current supply comprising modulating the amplitude of the supply current in the three phases by three modulating waves of the same frequency, said frequency being an integral sub-multiple of the supply frequency and the three waves being relatively displaced from one another in time by one-third of the period of a complete cycle of the modulating waveform.

Claim 2

Dependent Claim 71 words

rA method of speed-changing for a three-phase induction motor supplied from a three-phase alternating current supply comprising modulating the amplitude of the supply current in the three phases by three modulating waves of the same frequency, said frequency being an integral sub-multiple of the supply frequency and the three waves being relatively displaced from one another in time by one-third of the period of a complete cycle of the modulating waveform.

Claim 3

Independent Claim 71 words

A method of speed-changing for a three-phase induction motor supplied from a three-phase alternating current supply comprising modulating the amplitude of the supply current in the three phases by three modulating waves of the same frequency, said frequency being an integral sub-multiple of the supply frequency and the three waves being relatively displaced from one another in time by one-third of the period of a complete cycle of the modulating waveform.

Claim 4

Independent Claim 71 words

A method of speed-changing for a three-phase induction motor supplied from a three-phase alternating current supply comprising modulating the amplitude of the supply current in the three phases by three modulating waves of the same frequency, said frequency being an integral sub-multiple of the supply frequency and the three waves being relatively displaced from one another in time by one-third of the period of a complete cycle of the modulating waveform.

Claim 5

Dependent Claim 7 words

of the same frequency as each other;

Claim 6

Dependent Claim 7 words

of the same frequency as each other;

Claim 7

Dependent Claim 14 words

equal in frequency to a selected integral submultiple of the said first frequency; and

Claim 8

Dependent Claim 14 words

equal in frequency to a selected integral submultiple of the said first frequency; and

Claim 9

Dependent Claim 26 words

A method of speed-changing as claimed in claim 1, in which the three modulating waves are square waves having the relative amplitudes +1 and -1 only.

Claim 10

Dependent Claim 22 words

A method of speed-changing as claimed in claim 1, in which the supply phase sequence and the modulating sequence are the same.

Claim 11

Dependent Claim 97 words

spaced apart in time equal to one-third of the period of one cycle of the control waveform; providing three groups of switch devices, one group in each phase of the three-phase supply, arranged to permit current flow in one sense for one polarity of an applied control potential and in the opposite sense for the opposite polarity of the applied control potential; applying the three said control waves to the three said groups of switch devices; and supplying to the said induction motor the three-phase currents permitted to flow by the said three groups of switch devices.

Claim 12

Dependent Claim 97 words

spaced apart in time equal to one-third of the period of one cycle of the control waveform; providing three groups of switch devices, one group in each phase of the three-phase supply, arranged to permit current flow in one sense for one polarity of an applied control potential and in the opposite sense for the opposite polarity of the applied control potential; applying the three said control waves to the three said groups of switch devices; and supplying to the said induction motor the three-phase currents permitted to flow by the said three groups of switch devices.

Claim 13

Dependent Claim 22 words

A method of speed changing as claimed in claim 1, in which the supply phase sequence and the modulating sequence are opposed.

Claim 14

Dependent Claim 27 words

A method of speed changing as claimed in claim 1 in which the modulating frequency is progressively changed to provide stepwise speed change over a speed range.

Claim 15

Dependent Claim 92 words

A motor control circuit arrangement for changing the speed of an induction motor having a delta-connected three-phase stator winding wIth phase-winding ends brought out to six terminals, comprising six pairs of controlled rectifiers connected in pairs from each phase-winding terminal, the one to the corresponding supply phase and the other to the supply phase next in arbitrary sequence, and rectifier control means for controlling said rectifiers so as to permit current flow in one sense for a modulating wave positive half cycle and in the opposite sense for a negative half cycle.

Claim 16

Dependent Claim 92 words

A motor control circuit arrangement for changing the speed of an induction motor having a delta-connected three-phase stator winding wIth phase-winding ends brought out to six terminals, comprising six pairs of controlled rectifiers connected in pairs from each phase-winding terminal, the one to the corresponding supply phase and the other to the supply phase next in arbitrary sequence, and rectifier control means for controlling said rectifiers so as to permit current flow in one sense for a modulating wave positive half cycle and in the opposite sense for a negative half cycle.

Claim 17

Dependent Claim 101 words

A motor control circuit arrangement as claimed in claim 6, wherein said rectifier control means comprises three-phase carrier-wave; zero crossing detection means and corresponding pulse generating means, summing means for summing said pulses for all three phases preset pulse counting means for counting a predetermined number of said pulses and for providing an output pulse identifying each said predetermined count, thereby to define a modulation frequency which is a predetermined sub-multiple of said carrier wave frequency, and logic means controlled both by said identifying output pulses and by said zero crossing pulses for providing inhibition control signals for said controlled rectifiers.

Claim 18

Dependent Claim 46 words

A motor control circuit arrangement as claimed in claim 7, in which the three-phase zero-crossing detection means comprises a phase-splitter for deriving all three phase waves from a single phase input, high-gain differential amplifiers for providing corresponding rectangular waves and rectifier-differentiator circuits for identifying each zero-crossing.

Claim 19

Dependent Claim 71 words

A motor control circuit arrangement as claimed in claim 7, in which the preset counter comprises a plurality of bistable elements connected in sequence, each providing alternative Q an Q outputs and switch means for preselecting a total count. an A motor control circuit arrangement as claimed in claim 9, in which the preselected switched output is fed to an AND gate to provide a output pulse identifying each preset count.

Claim 20

Dependent Claim 87 words

A motor control circuit arrangement as claimed in claim 7, in which the logic means comprises first, second and third groups of three AND gates, the first group having phase A, B and C zero-crossing pulse inputs respectively and all receiving the preset counter output pulse as second input, the outputs of the first group being supplied to corresponding ones of both second and third groups and the second and third gate groups receiving a second input corresponding to the different alternate pulses from said preset counter.

Claim 21

Independent Claim 48 words

A method of changing the running speed of a three-phase induction motor fed from a three-phase alternating current supply of a first frequency by supplying the motor with three-phase current of a second frequency, comprising the following steps: deriving from the three-phase supply three control waves which are;

Claim 22

Independent Claim 48 words

A method of changing the running speed of a three-phase induction motor fed from a three-phase alternating current supply of a first frequency by supplying the motor with three-phase current of a second frequency, comprising the following steps: deriving from the three-phase supply three control waves which are;

Claim 23

Dependent Claim 27 words

A method of changing the running speed of a three-phase induction motor as claimed in claim 12, in which the three control waves are of rectangular waveform.

Claim 24

Dependent Claim 35 words

A method of changing the running speed of a three-phase induction motor as claimed in claim 12, in which the phase-sequence of the said three control waves is the same as the said three-phase supply.

Claim 25

Dependent Claim 36 words

A method of changing the running speed of a three-phase induction motor as claimeD in claim 12, in which the phase-sequence of the said three control waves is opposite to that of the said three-phase supply.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1975-11-21	1976-05-22	1976-11-21	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1979-11-21	1980-05-22	1980-11-21	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1983-11-21	1984-05-22	1984-11-21	$7700.00	Window Closed / Lapsed

Three-phase induction-motor, speed-changing method and control circuit

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