Hobbies And Interests
Protecting Equipment
Surges caused by lightning can send thousands of volts through a circuit. The type of filter capacitor used in power-line filters is called a ̶0;line-filter.̶1; With high capacitance and durability, they absorb line surges so that they aren't passed on to other circuits and equipment farther down the line. This keeps the power transients and Electro-Magnetic Interference, or EMI, away from sensitive components, saving time and money that would normally be spent repairing them.
Smoothing DC Power
After an AC signal leaves a transformer through diodes, it becomes a DC signal. A filter circuit is used to smooth out the uneven DC signal. In this role, filter capacitors are positioned between the ground and the DC line, and their capacitance is selected to give the circuit a particular Timing Constant. The TC indicates the speed at which a circuit adapts to voltage variation ̵1; with the right TC, the output voltage is converted to a smoother DC.
Spark Quenching
A Spark Quencher is a capacitor and a resistor connected in series, designed to absorb high-power surges. The SPQ withstands back-EMF, which happens when the power is removed from an inductive element in a device such as a motor or solenoid, sending a spike into the power line. These surges can be very large ̵1; over a thousand volts ̵1; and the role of the SPQ is to absorb it, and release it slowly at a lower power level.
TRIAC Protection
Filter capacitors are also used to protect solid-state switches such as TRIACs, as well as similar devices like field-effect transistors and silicon-controlled rectifiers. The filter capacitor, usually 0.01 to 2 micro farads, is connected in series with a resistor, making this circuit a form of SPQ. The capacitor and resistor are positioned to protect the switch from surges. As the load goes up, the size of the capacitor needed increases while the value of the resistor decreases.