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| | | POWER | | |
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| | | Power Supply Magnetics- Donald E. Pauly, Consultant Sponsored by The Arnold Engineering Company, Marengo, Illinois | | |
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| | | Many trade-offs are possible in selecting the optimum HF core material for a specific application. Factors like volume, sound level, and cost enter into the decision. | | |
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| | | nations. The test circuit must be able to survive the shorting of the capacitor under test. For testing, an over height version of the 26 permeability 5.2 inch diameter Arnold Hi-FLUX™ core was resonated with a I2uT polypropylene capacitor. This combination was driven by a power MOSFET switch operating from ±25V variable supplies. From low to high drive levels, resonance shifts from 190 Hz to 235 Hz. Figure 28 shows that the inductor current departs considerably from a sine wave due to reduction in AC permeability at high peak currents. The core weighs about 31bs and the | | |
| | | winding weighs about 5Ibs. At full output, the Q is about 30. The operating frequency ispicked below thefrequencyofmaximumQtokeep the capacitor current low. About 210W is required fo drive thecapaci-tor to 600VRMS. Forced aircooling for the windings is required for more than a few minutes operation. After dipping in T-84 silicone, the core withstood ±3kV at 10kHz with no signs of corona. To test this type of capacitor with 60 Hz AC would require a variac and transformer combination weighing about 301bs. Furthermore, a industrial circuit breaker would be too slow to prevent capacitor destruction from momen- | | |
| | | Hi-FLUX | | (HF) cores | |
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| | | can store very large amounts of energy for their size. They can operate up to 14 kilogauss with moderate loss. Among their many applications are industrial test sets, RFI power line filters, and battery line filters. For capacitor testing, high voltage polypropylene capacitors can be resonated with a high frequency inductor that employs an HF core. These capacitors have very low losses and are commonly rated at480VRMS and 80 A, Such capacitors find application in welders using SCR converters and as snubbers in GTO SCR power supplies for locomotive drives. The testing must be done with AC rather than DC to discover problems with lead attachments and end termi- | | |
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| | | 120V 60Hz | | |
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| | | 425W Sodium Vapor Ballast Load | | |
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| | | TfoOO (IF M-1-: | | |
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| | | Figure 28. 60nH @15A 5.2-in. HF Core Sinewave: 300V/dlv., Triangle Wave: 10A/ div.; Sweep: 2:msec/div. | | |
| | | Figure 29a. Sodiium Vapor Lamp. 42SW Ballast Load | | |
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| | | 14 POM ■ 1996 | | |
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