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Surge protector

A surge protector is an equipment that protects the machines against surges that comes from the source or inside the facility. Inside this device, there is a zinc oxide varistor, which allows the electric current to pass through it if only the voltage is greater than the rated. (mais…)

Power consumption of a CRT monitor

I believe everybody wants to save energy, so I will share some measures that I made years ago with my old CRT monitor 17 inches for different conditions:
(for such measurements, I used a clamp ammeter and I considered power factor equal to 0.80) (mais…)

Electric shock

Electric shock is established when our body behaves as a part of the circuit, offering a way for the current pass. This way is the one which offers less resistance.

It can have many causes, such as: contact with wires or sources energized, insulation failure, nature disturbances, accidental energizing, maneuver mistakes, electric arc (arc usually comes with severe burns, due to large amount of heat released). (mais…)

Differential residual circuit breaker

A differential residual device (known as DR in Brazil) acts through according the difference between two variables (in our case, currents). There is a toroid inside the enclosure which has a coil for each input. Among these, there is also a auxiliary coil connected to a cut relay. (mais…)

Fluorescent lamps

A lot of things is spoken about economy in our bills provided by fluorescent lamps. They dissipate 80% less then tungsten ones (incandescents); so, tendency is to think that they’re friend of nature or more environmentally friendly.

But, is it really true? Let’s review some points: (mais…)

Switching the machines off

Switching a electrical machine off is often misguided. Its best idea can be: a set of procedures that provides total elimination of electrical hazards in the shutdown of a machine (or a system).

 The simple turning off action in the circuit breaker does not guarantee a safe condition for work. (mais…)

Grounding system

A grounding is the intentional connection of a electric to the Earth. It can be: protective, functional or temporary.

Protection: provides electric protection for human beings by offering a scape way to the current.
Functional: the Earth is used as a return conductor. (mais…)