List of Nikola Tesla patents

 - Commutator for Dynamo Electric Machines - 1886 January 26 - Elements to prevent sparking on dynamo-electric machines; Drum-style with brushes.
 - Electric Arc lamp - 1886 February 9 - Arc lamp with carbon electrodes controlled by electromagnets or solenoids and a clutch mechanism; Corrects earlier design flaws common to the industry.
 - Electric arc lamp - 1886 February 9 - Arc lamp's automatic fail switch when arc possesses abnormal behavior; Automatic reactivation.
 - Regulator for dynamo electric machines - 1886 March 2 - Two main brushes connected to helices coil ends; Intermediate point branch shunt connection for third brush.
 - Regulator for Dynamo Electric Machines - 1886 March 2 - Auxiliary brush[es] shunting a portion or whole of the field helices coil; Regulates energy flow; Adjustable level of current.
 - Regulator for Dynamo Electric Machines - 1886 October 19 - Automatic regulation of energy levels; Mechanical device to shift brushes.
 - Dynamo electric machine - 1887 March 22 - Improve construction; Facilitate easier construction; Reduce the cost; Magnetic frame; Armature; Alternating current synchronous motor.  
 - Electro magnetic motor - 1888 May 1 - Mode and plan of operating electric motors by progressive shifting; Field Magnet; Armature; Electrical conversion; Economical; Transmission of energy; Simple construction; Easier construction; Rotating magnetic field principles.
 - Electro Magnetic Motor - 1888 May 1 - Novel form and operating mode; Coils forming independent energizing circuits; Connected to an alternating current generator; Synchronous motor.
 - System of Electrical Distribution - 1888 May 1 - Current from a single source of supply in the main or transmitting circuit induce by induction apparatus; Independent circuit(s); Electric distributor.
 - Electro Magnetic Motor - 1888 May 1 - Rotation is produced and maintained by direct attraction; Utilizes shifting poles; Induction magnetic motor.
 - Electrical Transmission of Power - 1888 May 1 - New method or mode of transmission; Dynamo motor conversion with two independent circuits for long distance transmission; Alternating current transmission; Includes a disclaimer; Economic; Efficient.
 - Electrical Transmission of Power - 1888 May 1 - Improvements in electromagnetic motors and their mode or methods of their operations; Motor is wound with coils forming independent circuits on the armature; Armature is mounted to rotate between two different poles; Armature will eventually synchronize with that of the generator; Windcoils or coils on the field magnets; Expose to continuous current to maintain a permanent field.
 - Method of Converting and Distributing Electric Currents - 1888 May 1 - Related to electric distribution systems; Current is from a single main source or suitable transmitting circuit; Induction into an independent circuit; Divide the current from a single source; Transformations; Discovery of method to avoid prior liable and dangerous methods; True Dynamic induction.
 - Commutator for dynamo electric machines - 1888 May 15 - Relates to dynamo-electric machines or motors; Improvements on devices to collect or communicate currents; Avoids destruction and wear of machine; Avoid adjustments due to destruction and wear; Enable practical construction of very large dynamo electric machines or motors with the minimum number of communicator segments; Increases safety and efficiency.
 - System of electrical distribution - 1888 October 2 - Related to previous electric distribution systems developed by Tesla; Examples of systems in operation with motors or converters, or both, in parallel; Examples of systems in parallel; Examples of systems in series.
 - Dynamo Electric Machine - 1888 October 2 - Related to the patents of Tesla and Charles F. Peck, numbers: US381968 and US382280; Ordinary forms of continuous and alternate current systems may be adapted to Tesla's system, with slight changes to the systems; Effects their forms; Only the best and most practical solutions are presented to the three most common forms of the devices applicable; Illustrated are the continuous (or closed) circuit machines, machines possessing armatures with coils connected diametrically (known as "open-circuits"), and machines with armature-coils of which have a common joint.
 - Dynamo Electric Machine or Motor - 1888 October 2 - Improvement in the construction of dynamo or magneto electric machines; Novel form of frame and field magnets that renders the machine more sturdy and compact as a structure; Requires fewer parts; Less difficulty in construction; Lower expense; Useful to alternating and continuous current machines.
 - Dynamo Electric Machine - 1888 October 9 - Relates chiefly to the alternate current machine invented by Tesla; Related to patents numbered US381968 and US382280; Seeks to avoid mechanical drawback of running high frequency machines; Efficient at low speeds; Producing rotating magnetic poles in one element of the machine and drive the other at a different speed.
 - Regulator for Alternate Current Motors - 1888 October 9 - Improvement in the electrical transmission systems; Means of regulating and power of the motor or motors; Used with system of multiple motors primarily (or systems with motors and transformers) that have independent energizing circuits which act to set up progressive or shifting magnetic poles (i.e. the rotating magnetic field); Controls the speed of the motor.
 - Thermo Magnetic Motor - 1888 January 15 - Widely known that heat applied to a magnetic body will lessen its magnetizing ability; High enough temperatures will destroy the magnetic field; Mechanical power by a reciprocating action obtained from the joint action of heat, magnetism, and a spring or weight (or other force); In this patent, the application of heat to a body that is magnetized by induction or otherwise to the action of heat until the magnetism is neutralized to allow a weight or a spring to give action and lessen the action of the heat to restore the magnetic effect to move the body in the opposite direction. 
 - Method of Operating Electro Magnetic Motors - 1889 April 16 - Improvements to previous instances of synchronous motors; Previous instances of synchronous motors have not been started by the alternating current generators; New discovery of simple method or plan of operating such motors; Requires no other device other than the motor itself; Conversion from a double circuit motor and which will start under the actions of an alternate current into a synchronizing-motor; synchronous motor definition.
 - Electro Magnetic Motor - 1889 June 25 - Torque, instead of being the result in the difference in the magnetic periods or phases of the poles or to the attractive parts to whatever due, is produce to the angular displacement of the parts which, though movable with the respect to one another, are magnetized simultaneously, or approximately so, by the same currents; Concerns the armature and the field laminations of the magnetic core for the greatest magnetic attractions; Best means to achieve these results.
 - Method of Electrical Power Transmission - 1889 June 25 - New and useful method of bringing up the motor to a desirable speed; Forms of alternating current machines, connected to alternating current generators, can be run as synchronous motor; Prior, alternating current will not start it; Construct a generator with two coils or sets of coils and connect them with a motor of corresponding coils or sets of coils; By means of two line wires, the motor and generator in like fashion; Related to US 390413 (for means of starting); Will operate as a single-circuit synchronizing system.
 - Dynamo Electric Machine - 1889 July 16 - Relates to class of machines referred to as "Unipolar" machine (i.e., a disk or cylindrical conductor is mounted in between magnetic poles adapted to produce a uniform magnetic field); Construction of a machine with two fields, each having a rotary conductor mounted between its poles; Discussed the disk form primarily; The direction of the magnetism or order of the poles in one field of force is opposite to that of the other, so the rotation of the disk in the same direction forms a field from the center to the circumference and another from the circumference to the center; Contacts applied to the shafts form terminals of a circuit to produce a sum of electromotive forces of the two disks; If direction of the fields are the same, driving the disks in the opposite direction will obtain the same results.
 - Method of Obtaining Direct current from Alternating Currents - 1889 October 22 - Superiority of alternating currents discussed; Delineates machines to convert alternating currents to direct (or continuous) currents at will at one or more points; Obtain direct currents from alternating currents; Active resistances to opposite electrical character, whereby the currents or current-waves of opposite character will be diverted through different circuits.
 - Electro-Magnetic Motor - 1889 December 3 - Induction motor with two or more energizing circuits; alternating currents of differing phases are passed to produce rotation or operation of the motor; simple way consists of two circuits; alternate way consists of one line that divides the alternating current in the motor circuit and effects an artificial lag in one of the circuit of branches (such as by a different induction capacity).
 - Method of Operating Electro-Magnetic Motors - 1889 December 3 - Related to US401520; Alternative improvements to synchronous motors; Torque and synchronous actions in motors; different field circuit of differing induction; Windings and shunts; Increases tendency to synchronize.
 - Electro-Magnetic Motor - 1889 December 3 - Induction motor operation with two or more windings; securing differing phase differences; Phase proportional to the induction and inverse to the resistance encountered by the current; one circuit (the energizing circuit) should have high induction and low resistance (along with possessing the greater length or number of turns) and the converse in the other (which has few turns of finer wire or wire that has higher resistance); magnetic quantities of the poles should be approximately equal; Self-induction cores are much longer.
 - Electric Motor - 1889 December 3 - Drawings include the motor seen in many of Tesla's photos; Classic alternating current electro-magnetic motor; Induction motor operation; Field and armature of equal strengths or magnetic quality; field and armature cores of equal amounts; Coils containing equal amount of copper.
 - Electro-Magnetic Motor - 1889 December 3 - Induction motor operation with two or more windings; Differing phases; Structural and operational conditions; Armature operation conditions and the obedience to the energizing circuit and stator; Construction and organization principles.
 - Armature for Electric Machines - 1889 December 24 - Construction principles of the armature for electrical generators and motors; Simple and economical; Coils of insulated conducting wire (or ribbon) may be wound or formed into bobbins; Position of the bobbins dictate the windings; Armature has polar projections and maximum core-surface exposure to the field magnetic poles; Related to other applicant patents, numbers US327797, US292077, GB9013.
 - Electro-Magnetic Motor - 1889 December 31 - Electric generator; Employment of an artificial cooling device; Enclosing the source of heat and that portion of the magnetic circuit exposed to the heat and artificially cooling the said heated part; Combination of an enclosed source of heat applied to a portion of said core; Magnetized core or body and a conductor within the field of force; Artificial cooling device for reducing the temperature of the heated portion thereof; Means for bringing a cooling gas or fluid in contact with the heated portion of the core, and means for controlling the admission of the same; The combination and coils wound thereon and a connection with a boiler for admitting steam into the channels, as set forth; Magnetized core containing passages or channels; Means for applying heat to a portion of the core.
 - Electro-Magnetic Motor - 1890 March 25 - Cites then common language of his motors referred to as the "magnetic lag" motors; Another form of the induction motor with two or more energizing circuits with differing phase differences are passed to produce rotation or operation of the motor; Magnetism lags electrical parts of energizing effects; Manifests these effect simultaneously and not successively; Related to US405858; Torque is produced to the angular displacement of parts; Best means to achieve these results; prefer the use of alternating currents.
 - Pyromagneto Electric Generator - 1890 May 13 - Electric generator; Employment of an artificial cooling device; Enclosing the source of heat and that portion of the magnetic circuit exposed to the heat and artificially cooling the said heated part; Combination of an enclosed source of heat applied to a portion of said core; Magnetized core or body and a conductor within the field of force; Artificial cooling device for reducing the temperature of the heated portion thereof; Means for bringing a cooling gas or fluid in contact with the heated portion of the core, and means for controlling the admission of the same; The combination and coils wound thereon and a connection with a boiler for admitting steam into the channels, as set forth; Magnetized core containing passages or channels; Means for applying heat to a portion of the core.
 - Alternating-Current Electro-Magnetic Motor - 1890 August 5 - Rotation of an electromagnetic motor is produced by the magnetic movements or the maximum of the pole's (or point's) magnetic effects from the conjoined actions (or the two energizing circuits) through which alternating currents (or similar rapidly varying currents) are passed through; Multiple magnets are powered by artificial currents; Inverse strength of magnetism on stator for best rotation; Creates multiple phases through one circuit from one power source.
 - Alternating-Current Motor - 1890 August 5 - Two sets of field-pole pieces of energized independently by the same source; Closed magnetic iron shunts or bridges in sets or series.
 - Electrical Transformer Or Induction Device - 1890 August 5 - Main magnetic core and the primary and secondary coils interposed by a magnetic shield or screen between the coils or around one of the coils; Coils can be wound upon or built up around the magnetic shield; Adapted to or capable of being magnetically saturated by a predetermined current strength below the maximum in the primary.
 - Electro-Magnetic Motor - 1890 August 5 - Describes the combination, in an alternating current motor, of an energizing coil and a core composed of two parts (one being protected from magnetization from the other one interposed between it and the coil); A rotating armature is motivated by the induced fields; Alternatively, a field magnet composed of a coil and core (with two sections in proximity of the coil and an inner section between the same); Also, a field magnet each composed of a coil and core (with two sections in proximity of the coil and an inner section between the same).
 - Electro-Magnetic Motor - 1891 January 27 - Describes the combination, in a motor, of a primary energizing circuit (connected to a generator) and a secondary circuit in inductive relation to the primary; Each circuit has a different electrical character, resistance, induction capability, or number and type of windings.
 - Method of Operating Arc-Lamps - 1891 March 10 - Abate or render inaudible sound emitted by arc lamps that are powered by (or supplied with) alternating currents by increasing the frequency of alternations (or pulsations) above the auditory level.
 - Alternating Electric Current Generator - 1891 March 10 - A generator that produces alternations of 15000 per second or more.
 - System of Electric Lighting - 1891 June 23 - Apparatus devised for the purpose of converting and supplying electrical energy in a form suited for the production of certain novel electrical phenomena, which require currents of higher frequency and potential.  It specifies an energy storage capacitor and discharger mechanism on the primary side of a radio-frequency  transformer.
 - Electro-Magnetic Motor - 1891 June 30 - Alternating current motor, with field magnets and energizing circuit armature-circuit and a core adapted to be energized by currents induced in its circuit by the currents in the field circuit; Condenser connected with or bridging the armature-circuit (e.g., the rotating element of the motor); Energizing circuit formed by coils wound thereon in a different inductive relations to the field and joined in a continuous or closed series; Combination of a condenser, the plates of which are connected, respectively, to the junctions of the circuits or coils.
 - Electrical Meter - 1891 June 30 - Method of computing the amount of electrical energy expended in a given time in an electrical circuit; Operates by maintaining by the current a potential difference between two conductors in an electrolytic solution (or cell) uniform throughout the whole extent of such conductors exposed to the solution; Measurement of the variation of the resistance in one or both conductors dues to the gain or loss of metal by electro-deposition; Electrolytic cell and conductors passing through the cell  and connected in series with a translating device; One or more resistances connected with the conductors and cell for establishing a potential difference between the two conductors through the solution of the cell; Tubular cell contains electrolytic solution and closed at each end.
 - Electric Incandescent Lamp - 1891 June 30 - Incandescent lamp consisting of two isolated refractory conductors contained in a non-striking vacuum and adapted to produce light by incandescence; Globe or receiver exhausted to the non-striking point with two mounted isolated bodies (or metal wires) of refractory conducting material to emit light and sealed in; Terminal to connect with an electrical energy source; Refractory conducting material not to be rendered incandescent coated or covered with insulation.
 - Electro-Magnetic Motor - 1891 September 22 - Alternating current non-synchronizing electric motor coupled with a synchronizing alternating current motor whereby the former starts the latter and throws it into synchronism with its actuating current; Switch mechanism for directing the current through either or both of the motors; Combination of two motors (one an alternating current torque motor [e.g., shifting poles via the energizing circuit] and the other a synchronizing alternating current motor) the armatures of which are mounted upon the same shaft; Switching circuit directing the alternating current or currents through the several circuits of one motor or the single circuit of the other.
 - Method of and Apparatus for Electrical Conversion and Distribution - 1891 November 3 - Apparatus devised for the purpose of converting and supplying electrical energy in a form suited for the production of certain novel electrical phenomena which require currents of higher frequency and potential.
 - Electro-Magnetic Motor - 1891 December 8 - Alternating current motor provided with two or more energizing or field circuits; One circuit connected to current source and the other (or others) in inductive relation thereto; One circuit connected to alternating currents and the other constituting high potential secondary circuit; Condenser interposed in the inductive circuit.
 - Electrical Condenser - 1891 December 8 - Electrical condenser composed of plates or armatures immersed in oil; Plates or armatures can be adjustable.

Question: What was Nikola Tesla's first patented invention?