Distinguishing motor starts from short circuits through phase-angle measurements.
Yenchek-MR; Cawley-JC; Peterson-JS; Kohler-JL
NIOSH 1997 Mar; :1-15
An investigation was undertaken to investigate the characteristics of high voltage underground electrical mining equipment motor start and short circuit waveforms. The aim of the study was to determine a method for providing short circuit protection without intentional time delays to account for motor starts. Computer simulations of power systems identified the requirement for accurate and rapid detection systems. Analyses of high voltage longwall coal mine power systems were conducted using commercial power system analysis software. Distribution voltage, transformer impedance, power center location, and motor size affected magnitude of short circuits and motor start currents. Phase angles between voltage and current were longer for motor starts than for short circuits. A prototype with an induction motor was developed and tested in the laboratory. Minimizing the intentional time delays in short circuit protection will help ensure temperatures of ignition thresholds for gas and dust are not be exceeded on energized electrical apparatus surfaces.
NIOSH-Author; Mining-industry; Underground-mining; Mining-equipment; Electrical-equipment; Electrical-properties; Electronic-circuits; Voltage-regulation
Numbered Publication; Report of Investigations
NTIS Accession No.
DHHS (NIOSH) Publication No. 97-120; RI-9638
National Institute for Occupational Safety and Health