EET 110 - Survey of Electronics Chap. 18 - Circuit protection devices Chap. 19 - Electric Power
Dec 20, 2015
Undesirable Circuit Cond.
• Overloads - excessive current for wire size.– Ampacity determined by size of wires used
• Short Circuits– Special case of Overloads - 0 load resistance
• Ohms law says I = V/R = V/0 =
Fuse and Circuit Breakers
• Rated in amps
• Fuse consists of link that melts at a rated current - opening circuit
• Breaker heats a bi-metal strip that opens circuit mechanically
Testing Fuses
• Using a continuity tester
• Ohmmeter – Good fuse tests ~ 0 ohms– Blown fuse = infinity (OL)
• To replace fuses – use fuse puller
Other Circuit protections
• Thermal Overload Protection– Motors, computer power supplies
• Lightening Rods/Arresters– Surge Suppression
• Power conditioning– Eliminate RF noise – Produce sinusoidal voltage
Alternative Generation
• Wind power
• Solar Power– Photo-voltaic cells
• Magneto Hydrodynamics– Use plasma as part of generation current flow
Fuel Cell
• Converts hydrogen directly to electricity
• Ballard Fuel Cell– Uses PEM technology
• Proton Exchange Membrane (PEM) Fuel Cells
Power Transmission
• Distribution to from the generation facility to the customer.
• Sequence of step-up / step-down transformation