Peak Voltages With D-C Arc Interruption for Aircrart

The data presented may be summarized as follows: 1. When a Switchette (the trade name for a small double-break switch with 0.020-inch gaps and opening time of one to two milliseconds) was used on 250 volts and 0.4 ampere at sea level, voltage peaks as high as 28 times line voltage or 7,000 volts were observed. 2. A maximum peak of 130 times line voltage or 3,900 volts was observed while operating the Switchette double-break on 30 volts and 0.4 ampere at sea level. 3. When the Switchette was used the voltage peaks were found to decrease with altitude for all voltages tested. A maximum of seven to one in ratio of voltage at sea level to voltage at 50,000 feet was observed. 4. Using a double-break contactor which has a 1/16-inch gap per break and a gap-travel time of 12 milliseconds, the induced voltage peaks rise with altitude in every case. A maximum of two to one in the ratio of voltage at 50,000 feet to voltage at sea level was observed. The loads on which these tests were made, as the text of the paper will show, were very much less inductive than those used for the Switchette. 5. Variations of humidity over a wide range has little effect on the voltage peaks at any altitude. 6. There are no voltage peaks above normal line voltage in a purely resistive circuit.