Tesla Self-Starting Alternating Motor System

Friday, July 19, 1889
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TESLA SELF-STARTING ALTERNATING MOTOR SYSTEM. As is well known, certain forms ui alternating-current machines have the property, when connected in circuit with an alternating-current generator, of running as a motor in synchronism therewith; hut, while the_alter- nating current will run the motor after it has attained a rate of speed synchronous \vith that of the generator, it will not start it; hcnce, where these “synchronising motors," as they are termed, have been run, some means have heen employed to bring the motors up to synchronism with the generator before the alternating current oi the generator is applied to drive* them. In some instances mechanical appliances have hccn utilised for this purpose. ln others special forms of motor have been constructed. \\'ith the object of affecting the starting of the alter- nating motor and bringing it to synchronism \vithout external aid, Mr. Nikola Tesla has devised a simple system, in which he employs an earth return during the period of starting only. For this purpose he constructs a generator with two coils or sets oi coils, and a motor with corresponding energising coils or se‘s of coils. By means of two line~\vires, one terminal of e»ch g0l\€l`2\t0l`-C0ll is connected ti one terminal of its corresponding motor~ coil while the opposite terminals of the generator coils are joined together, and likewise those of the motor. To start the motor, an electrical connection is temporarily established between the points of connection between the coils in the generator and those in the motor, so that the system becomes an ordinary donhle»cireuit system. When by this plan of connection the motor has attained the desired speed, the earth connection is severed, hy which mem s the system becomes an ordinary single-circuit synchronising system. The accompanying diagram shows the manner in which this is accomplished, G representing an ordinary alternating-current generator having four field- poles, A, magnetised by a continuous current, and an armature wound with two coils, C, connected together in series. G M V1 [ _ s M <' , \\ li I I \ ' » =;.‘=:~;i s. :_ Ls- E_-L _'_- IQ P I J' ` » I ` ' M represents an alternating-current motor \vith, say, four poles, D, the coils on which are connected in pairs, and the pairs connected in series. The motor armature should have polar projections and closed coils, E, From the common joint or union between the two coils ofihoth thc generator and motor an earth connection, F, is established, while the terminals or ends of the coils which they form are connected to the line-conductors. Assuming that the motor is a synchronising motor, or one that has the capability of running in synchronism with the generators, but not of starting, it may be started by the above-described plan by closing the ground connection from both gov crator and motor. The system thus becomes one with a two-circuit generator and motor, the ground forming a common return for the currents in the two-line wires. When by this arrangement of circuits the motor is brought to speed, the ground connection is broken between the generator or motor, or both, and ground switches, K K, being employed for this purpose. The motor thon runs as a synchronising motor.