<P> Two years after signing the Tesla contract, Westinghouse Electric was in trouble . The near collapse of Barings Bank in London triggered the financial panic of 1890, causing investors to call in their loans to W.E. The sudden cash shortage forced the company to refinance its debts . The new lenders demanded that Westinghouse cut back on what looked like excessive spending on acquisition of other companies, research, and patents, including the per motor royalty in the Tesla contract . At that point, the Tesla induction motor had been unsuccessful and was stuck in development . Westinghouse was paying a $15,000 - a-year guaranteed royalty even though operating examples of the motor were rare and polyphase power systems needed to run it were even rarer . In early 1891, George Westinghouse explained his financial difficulties to Tesla in stark terms, saying that, if he did not meet the demands of his lenders, he would no longer be in control of Westinghouse Electric and Tesla would have to "deal with the bankers" to try to collect future royalties . The advantages of having Westinghouse continue to champion the motor probably seemed obvious to Tesla and he agreed to release the company from the royalty payment clause in the contract . Six years later Westinghouse would purchase Tesla's patent for a lump sum payment of $216,000 as part of a patent - sharing agreement signed with General Electric (a company created from the 1892 merger of Edison and Thompson - Houston). </P> <P> The money Tesla made from licensing his AC patents made him independently wealthy and gave him the time and funds to pursue his own interests . In 1889, Tesla moved out of the Liberty Street shop Peck and Brown had rented and for the next dozen years would work out of a series of workshop / laboratory spaces in Manhattan . These included a lab at 175 Grand Street (1889--1892), the fourth floor of 33--35 South Fifth Avenue (1892--1895), and sixth and seventh floors of 46 & 48 East Houston Street (1895--1902). Tesla and his hired staff would conduct some of his most significant work in these workshops . </P> <P> In the summer of 1889, Tesla traveled to the 1889 Exposition Universelle in Paris and learned of Heinrich Hertz' 1886--88 experiments that proved the existence of electromagnetic radiation, including radio waves . Tesla found this new discovery "refreshing" and decided to explore it more fully . In repeating, and then expanding on, these experiments, Tesla tried powering a Ruhmkorff coil with a high speed alternator he had been developing as part of an improved arc lighting system but found that the high frequency current overheated the iron core and melted the insulation between the primary and secondary windings in the coil . To fix this problem Tesla came up with his Tesla coil with an air gap instead of insulating material between the primary and secondary windings and an iron core that could be moved to different positions in or out of the coil . </P> <P> On 30 July 1891, aged 35, Tesla became a naturalized citizen of the United States . In the same year, he patented his Tesla coil . </P>

Who is the inventor of the tesla coil