A 3-PHASE SAG GENERATOR FOR TESTING INDUSTRIAL-EQUIPMENT

A diesel powered three-phase standby 480V, 15kW, 60Hz synchronous gene rator has been modified to give controlled three-phase voltage sags. T hese sags can be controlled in both depth and duration. A 486-based co mputer with a data acquisition system controls the generator and monit ors the system under test. The custom software interface allows the us er to select the depth and duration of the each sag. Typically, the us er will select a series of sags in selectable increments down to a cer tain depth. The data acquisition system has both digital and analog in puts, so that data lines, sc and de voltages and currents, contactors and relays, etc can be monitored during the tests. The software interf ace enables the user to select allowable tolerance bands for the monit ored signals. If one or more of the signals falls outside the allowabl e range, the test is suspended, The sag depth and duration that caused the equipment to ''fail'' the test is then recorded, After testing ov er a range of sag durations, a CBEMA-type curve is available for the s ystem under test. The sag generator enables the user to systematically determine the sensitivity of the components of an installed process l ine, This will enable the user to determine cost-effective ride-throug h enhancement strategies or to test the effectiveness of currently ins talled equipment. Although this test generator is small, the basic con cept can be scaled up to the 2MVA range.