Up Time Magazine - February/March 2009 - (Page 39) Evaluation Within the challenge was also the challenge of obtaining information from an Electric Signature Analyzer (ESA), or Motor Current Signature Analyzer (MCSA). Because of specific interlocks within the variable frequency drive system in the vehicle, and the fact that we were using an AllAmericanHybrid.com™ owned vehicle for the experiment, we determined that the best approach would be to take current-only readings. Data would have to be taken while the vehicle was in motion and in hybrid or electric-only mode (less than 15 mph) so we had to decide whether or not we would use a device that required intrusive modifications to the vehicle, namely putting a hole through the firewall. The result was the selection of the ALL-TEST Pro, ATPOL II ESA device which has the unique ability to communicate via Bluetooth. This allowed us to mount the data collector under the hood (Figure 2) while an engineer operated a laptop within the truck to take data (Figure 3) and the driver controlled the SUV to keep it at a steady speed and in electric motor mode. manufactured 2-mode transmission, which is similar to the Allison Transmission, LLC, Indianapolis hybrid bus transmission. For the purpose of the test, all work was performed by SUCCESS by DESIGN® personnel at the GM Tech Center in Warren, Michigan. The Tahoe was operated in two-wheel drive mode for the duration of the tests which were performed in drive at 10mph, in reverse at 5mph, and in drive at variable speeds. The vehicle, itself, has been used to evaluate such things as mileage, which has ranged from 19.8mpg to 26.1mpg, depending on driving and weather conditions, and with just over 12,000 miles at the time of this study. Specific data on the components of the transmission were provided to SUCCESS by DESIGN® personnel for purposes of evaluation. Test Results One of the concerns was whether or not we could obtain data through the shielded cables that led from the drives to the transmission. The other primary concern was what the current data would look like as the motors were inverter-fed. The cables related to the lowspeed motor were identified and a one-thousand amp clamp connected to one lead. As the Tahoe was backed out of the garage it was observed that both concerns were unfounded because we were drawing well over 100 Amps that remained steady on the digital readout. Unfortunately, the ATPOL II does not display the spectra of the motor diagnostics nor allow the operator to watch real-time data and capture just the area of interest, so the testing and data capture was performed and the results provided afterward. The evaluation required a steady speed at about 10mph for about 1 minute in the forward direction, and then about 5mph in the reverse direction in a remote empty parking lot, then 1 minute at varying speeds back to the garage. The data was analyzed and all involved were impressed with the current and spectral data, which showed virtually no noise as compared to the noise generated in a commercial drive/motor combination. In the drive mode at 10mph, the results appeared as shown in Figures 4, 5 and 6. In Figure 5, there are line frequency side bands around the line frequency and multiple harmonics of twice line frequency in demodulated current, as shown in Figure 4. Upon review, we were able to determine that these were most likely the other motor in generat- Figure 2 - Data Collector Under Hood Figure 3 - Data Collection Computer The vehicle used was a 2008 four-wheel drive GM hybrid Tahoe manufactured in March, 2008, in Arlington Texas, using the Baltimore Powertrain (GM/Allison Transmission) www.uptimemagazine.com 39 http://www.AllAmericanHybrid.com http://www.alignmentsupplies.com http://www.uptimemagazine.com
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