Thrust control for linear motors

Claim 1

A control system for regulating voltage applied to a variable speed linear induction motor energized by a polyphase AC power source of a given base voltage, the system comprising: a. a stator adapted to be moved linearly with respect to a rotor member by the ineraction of magnetic forces therebetween; b. said stator consisting of a plurality of electrically uncoupled sections arranged in a spaced linear relation, said sections having coils therein, each of said coils having inlet terminals and control terminals; c. means for independently and sequentially connecting in parallel relationship each of said plurality of sections to said AC power source, wherein said inlet terminals in each stator section are connected to alternate phases; d. voltage control means connectable to a plurality of said stator sections, one at a time, across the control terminals thereof, said voltage control means being adapted to vary the voltage being delivered to the stator section to which it is connected from zero magnitude to that of the base voltage; e. switching means connected to a plurality of said stator sections to couple the respective control terminals thereof and cause the base voltage to be applied across the stator bank; and f. switching means connected in each circuit between the voltage control means and each of said stator sections, said switching means being adapted to disconnect said voltage control means from the associated stator section.

Claim 7

A method for controlling thrust of a linear induction motor as the speed of the motor is increased the method comprising the following steps: a. electrically decoupling a plurality of stator sections arranged in a spaced linear relationship, each of said sections having a plurality of coils with inlet and control terminals respectively; b. connecting the inlet terminals of each of said plurality of stator banks in parallel configuration to associated phase legs of a polyphase AC power source of a predetermined voltage magnitude; c. coupling a voltage control means across the control terminals of a first of said stator sections so as to complete a circuit comprising said power source, said first stator section and said voltage control means; d. increasing the voltage across said first stator section from a zero value to said predetermined voltage magnitude; e. short circuiting the control terminals of said first of said stator sections so as to apply said predetermined voltage thereto; f. uncoupling said voltage control means from said first stator section control terminals; g. coupling said voltage control means across the control terminals of a second of said stator sections to complete a second circuit; comprising said power source, said second stator section and said voltage control means; h. increasing the voltage across said second of said stator sections from zero to said predetermined voltage magnitude; i. duplicating steps (e) thru (h) with the remaining stator sections to sequentially energize them until the desired thrust of the motor is attained.

Claim 8

A method for controlling thrust of a linear induction motor as the speed of the motor is increased the method comprising the following steps: a. electrically decoupling a plurality of stator sections arranged in a spaced linear relationship, each of said sections having a plurality of coils with inlet and control terminals respectively; b. connecting the inlet terminals of each of said plurality of stator banks in parallel configuration to associated phase legs of a polyphase AC power source of a predetermined voltage magnitude; c. coupling a voltage control means across the control terminals of a first of said stator sections so as to complete a circuit comprising said power source, said first stator section and said voltage control means; d. increasing the voltage across said first stator section from a zero value to said predetermined voltage magnitude; e. short circuiting the control terminals of said first of said stator sections so as to apply said predetermined voltage thereto; f. uncoupling said voltage control means from said first stator section control terminals; g. coupling said voltage control means across the control terminals of a second of said stator sections to complete a second circuit; comprising said power source, said second stator section and said voltage control means; h. increasing the voltage across said second of said stator sections from zero to said predetermined voltage magnitude; i. duplicating steps (e) thru (h) with the remaining stator sections to sequentially energize them until the desired thrust of the motor is attained.