Slide 1IntroductionTopic 1: Why bother with AC Surge Protection?Some examples of surge voltage waveformsUnidirectional surge waveformLikely Rate of Surge OccurrencesLocation CategoriesCategories ExplainedCategories Explained (continued)…Available Transient Suppression DevicesAvailable Transient Suppression Devices (continued)Available Transient Suppression Devices (continued)…Category A Transient Suppression FiltersCategory B Transient Suppression FiltersCategory A Transient Suppression Filter ExampleCategory A resultsFor Vsource = 120Vac at 60Hz, with VT = 90V:Category A Transient Suppression Filter Example (continued)For Vsource = 6kVac at 3kHz, with VT = 600V:Category B Transient Suppression Filter ExampleCategory B Transient Suppression Filter SchematicNow, same procedure for Category B: For Vsource = 6kVac at 10kHz, with VT = 600V, and S4 set to 4000V (to emulate Gas Tube):Topic 2: Fuse SelectionSlide 24Slide 25Fuse ParametersSlide 27Fuse SelectionStandard Fuse ExampleStandard Fuse Example SchematicStandard Fuse Example Schematic ResultsConclusion11/27/02 D. Zhou, Ph.D.Project Presentation TemplateAC Surge Protection and Fuse SelectionPresented by:Godfrey de la TorreEE 136Fall 2003Professor ZhouDecember 6, 200311/27/02 D. Zhou, Ph.D.Project Presentation TemplateIntroduction• In today’s discussion, we will cover AC Surge Protection and Fuse Selection.• Many companies implement AC Surge Protection within their products: Belkin, and Newpoint, just to name a few. • The intended market for this application is primarily those of consumer electronics devices like notebook computers, desktop PC’s, televisions, and even audio receivers.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateTopic 1: Why bother with AC Surge Protection?• With many of today’s electronics using sensitive electronic controls, it becomes necessary to protect them from current spikes (surges) caused by lightning.• Lightning causes surges which may destroy sensitive circuitry.• It is not only important to understand why surges occur, but rather to understand that they will occur, and that it is important to guard against them at all costs.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateSome examples of surge voltage waveforms• The “Ring Wave” Surge Voltage Waveform According to IEEE Standard 587-1980, the most common voltage surge waveform is shown below:•This waveform is referred to as the “ring wave.”•This wave may vary from 5kHz to 500kHz, but a typical residential “ring wave” varies anywhere from 30kHz to 100kHz, and has an amplitude as high as 6kV at 200A.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateUnidirectional surge waveform•This waveform is the called the unidirectional wave.•This waveform most likely occurs near the “service entrance” of a building, and as a result carries more energy than the ring wave.•This wave may carry 6kV and 3kA.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateLikely Rate of Surge Occurrences• Some surge protection devices have limited lives, so it becomes imperative to consider the relative rate of surge occurrences.•Knowing the relative rate of exposure and the anticipated surge crest gives the designer an idea of the number of surges that may occur within a given area.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateLocation Categories•The surge stress to be expected depends upon the location of the equipment to be protected.•For equipment inside a building, the expected surge stress depends upon the distance between the equipment and the “service entrance.”•Category A – equipment located furthest from the service entrance.•Category B – equipment near the service entrance•Category C – equipment outside the building11/27/02 D. Zhou, Ph.D.Project Presentation TemplateCategories Explained•Category A – the lowest stress category since furthest from service entrance; applies to all outlets(#10 to #14 wire) 30 ft. from Category B, or to those outlets 60ft. from service entrance; voltage stress is 6kV with 200 A max•Category B – the highest stress conditions since closest to service entrance; includes bus panels, distribution lines, and lightning systems in commercial buildings; same stress as Cat. A but with 3000 A max• Category C – the location outside the building or at the service entrance; stress far greater than 6kVNote: Since most power supplies are indoors, this report covers only Category A and B designs.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateCategories Explained (continued)…11/27/02 D. Zhou, Ph.D.Project Presentation TemplateAvailable Transient Suppression Devices•Metal Oxide Varistors – at voltages below its turnover voltage, these passive elements exhibit high resistance; at voltages exceeding the turnover point, these elements sink excess current11/27/02 D. Zhou, Ph.D.Project Presentation TemplateAvailable Transient Suppression Devices (continued)•Transient Suppression Diodes – essentially two diodes back to back in a shunt configuration; used for its high clamping action to stop transients; its resistance is low in conduction11/27/02 D. Zhou, Ph.D.Project Presentation TemplateAvailable Transient Suppression Devices (continued)…•Gas-Filled Surge Arrestors – handles much larger current than previous devices; effectively shorts to ground when it conducts excess current11/27/02 D. Zhou, Ph.D.Project Presentation TemplateCategory A Transient Suppression FiltersThis circuit utilizes metal oxide varistors, transient suppressor diodes, inductors and capacitors. When L1 (a) and L1 (b) conductive excessive current, caps C2 and C3 are charged to a voltage which brings ZD1, ZD2, and ZD3 into conduction. Once these diodes enter conduction, they effectively create a short to ground, thereby protecting the load.11/27/02 D. Zhou, Ph.D.Project Presentation TemplateCategory B Transient Suppression FiltersThis design is usually reserved for higher-power applications (when compared to Category A designs), and as such, utilizes gas-discharge tubes, spark gaps, fast-acting fuses, as well as inductors and capacitors. The functionality of this design is similar to that of Category A: when fast transients enter this circuit, varistors V1 through V3, L1, L2, and capacitors C1 through C5 cause conduction in diodes D1 though D3, which short to ground, thereby protecting the load. This design (as well as the Category A design) offers full noise