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44 <br />-2- <br />We tested four operating configurations of the inverter As an exploratory test, we also measured a <br />fifth configuration at only one microphone position The tested configurations are shown in the <br />following table <br />Configuration <br />Input Voltage <br />Output Power <br />Blower Setting <br />1 <br />790V <br />100% (500kW) <br />Maximum <br />2 <br />850V <br />100% (500kW) <br />Maximum <br />3 <br />730 -745V' <br />100% (500k1At) <br />Maximum <br />4 <br />790V <br />50% (250k11V) <br />Maximum <br />5 <br />850V <br />50% (250kM <br />Maximum <br />'During this measurement, the voltage regulator was not operating properly The input voltage was observed <br />to oscillate between 730V and 745V <br />We understand from our discussions with AEI personnel that the operating conditions tested are <br />representative of a real -world installation <br />4 Data Collection <br />41 Measurement System Parameters <br />We measured the sound power levels using our standard testing suite <br />Instrument <br />Make / Model <br />Identification <br />Microphone Calibrator <br />Bruel & Kjaer 4231 <br />SIN 2292439 <br />Noise Meter <br />Norsonic N -140 <br />SIN 1403581 <br />Microphone Preamplifier <br />Norsonic N -1209 <br />SIN 12749 <br />Microphone <br />Norsonic N -1225 <br />SIN 96063 <br />The noise meter was calibrated to 94 dB at 1 kHz before and after the measurements The <br />n-ncrophone windscreen was used The Norsonic N -140 has an internal correction filter to correct <br />for the effects of the windscreen <br />4.2 Measurement Locations and Site Conditions <br />We collected data in the Solaron testing lab adjacent to the main fabrication area at the AEI facility <br />in Fort Collins, CO The testing lab measured approximately 13 41m x 19 51m x 3 35m The floor <br />is an exposed concrete slab, three of the walls are constructed using vinyl -faced gypsum board on <br />stud - framing, the remaining wall was open to the main fabrication area, the ceiling is a suspended <br />grid containing vinyl -faced gypsum board panels The testing area contains several workstations and <br />other inverters The inverter was placed near the center of the testing lab space, at least 5.5m from <br />any of the lab walls No workstations or other inverters were located within 4m of the inverter <br />However, the top of the inverter was only 1 14m below the suspended gypsum board ceiling In an <br />effort to reduce the effects of the ceiling on the measurements, several ceiling tiles above the <br />VIBRO ACOUSTIC CONSULTANTS • 490 POST STREET, SUITE 1427 • SAN FRANCISCO, CA • 94102 • USA <br />PHONE ( +1) 415 -693 0424 • FAX (+1) 415 693 1398 • INTERNET http • / /www va- consult com <br />