Current Limiting Reactors with Fire-Proof Insulation on the Conductor

In a previous paper, tests were described which proved conclusively that if conducting material were lodged between the turns of a reactor having bare conductor, the reactor would flash-over at the instant a failure occurred on the circuit in which the reactor was placed. In this paper, tests are described which were made during the development of a proper insulation for the conductor of reactors. Short-Circuit Tests. Reactors tested consisted of one reactor with enameled conductor and two reactors with asbestos insulated conductor; one having a thin covering of asbestos; the other a thicker covering. The reactor with enameled conductor flashed over during the first short-circuit test. That with a thin covering of asbestos stood one short circuit and arced over in the second short circuit. The reactor with the thick covering stood many short circuit tests without any failure or sign of distress. These tests established thefact that thin insulation on the conductor will not prevent such failures, even though it has sufficient dielectric strength to with stand the voltages placed across it for the reason that the magnetic force exerted on iron and steel objects will cause them to break through thin insulation. On the other hand, thick insulation will adequately protect the reactor from failure due to foreign substances. Thermal Tests. Thermal tests on the asbestos insulation established the following facts: First: That this insulation does not smoke excessively at temperatures below 350 deg. cent. Second: That it does not burn even at temperatures of melting copper.