# Why is Power Factor so Important?

The specifications of any electrical appliance working on AC supply, such as a refrigerator, a toaster, a fan, etc., list a minimum of three important parameters – Voltage, Wattage and PF. The voltage rating indicates the nominal operating voltage of the appliance, the wattage rating indicates the power the appliance will use when switched on. The third parameter, PF, stands for the Power Factor – usually a value between 0.6 and 1.0.

All electrical appliances consume power for operating or working such as for lighting, heating, motion, etc. The appliance transforms a major part of the consumed power into its intended activity and the rest is wasted as heat. The ratio of the power converted to useful work to the total power consumed is the efficiency of the appliance.

Of the power converted to useful work, only a part is used as true or real power and the balance as reactive power. Engineers express real power in W (Watts) and reactive power as VAR (Volt-Amperes-Reactive). The appliance converts the real power into actual work, while it needs the reactive power to sustain a magnetic field and this does not directly contribute to the actual work done by the appliance. Therefore, the real power is also called the working power, while the reactive power is called non-working power. The sum total of the working and non-working power of an appliance is called its apparent power, expressed as VA (Volt-Amperes) and is the product of the nominal operating voltage and the current consumed by the appliance when operating.

This phenomenon of reactive power is true mostly for inductive appliances such as motors, compressors or ballasts. Power Factor is the ratio of the real or working power to the apparent power – an indication of how effectively the appliance will be using electricity. The problem is, although you will be paying the electricity utility for the entire apparent power consumed, the appliance will be converting only the real power into useful work for you. Therefore, a higher PF rating for your appliance works to your advantage – choose one with PF as close to 1.0 as possible.

In reality, low PF is also a headache for the utility supplying you with power. This is best explained with an example. Let us assume you have an operation that requires 100KW to run properly. If you install a machine that has a PF of 0.8, it will chalk up 125VA on the Apparent Power meter, but will convert only 80% of its incoming power into useful work. Since the electricity utility will have to supply both active and reactive power to its consumers, the wasted power ends up heating the conductors of the distribution system, resulting in a voltage drop at the consumers end.

The simplest way of improving the power factor is to add capacitor banks to the electrical system. PF correction capacitors offset the reactive power used by inductive loads, thereby improving the power factor. That maximizes the current carrying capacity, improves the supply voltage, reduces transmission power losses and lowers electricity bills.

# What is a capacitor used for?

Just as a bucket holds water, a capacitor holds charge. In fact, the world’s first capacitor was in the shape of a jar and was aptly named the Leyden jar. However, the latest capacitors do not look anywhere close to a jar. In its simplest form, a capacitor has two conductive plates separated by a dielectric. This helps maintain an electric charge between its plates. Depending on the type, different materials are used for the dielectric, such as plastic, paper, air, tantalum, polyester, ceramic, etc. The main purpose of the dielectric is to prevent the plates from touching each other.

The Leyden jar was invented in the 18th century, at the Netherlands University. It was a glass jar coated with metal on both the inside as well as the outside, with the glass effectively acting as the dielectric. The jar was topped off with a lid. A hole on the lid had a metal rod passing through it, with its other end connected to the inner coat of metal. The exposed end of the rod culminated in a metal ball. The metal ball and rod was used to charge the inner electrode of the jar electrically. Experiments in electricity used the Leyden jar for hundreds of years.

A capacitor can be used in a number of different ways, such as for storing digital data and analog signals. The telecommunication equipment industry uses variable capacitors to adjust the frequency and tuning of their communications equipment. You can measure a capacitor in terms of the voltage difference between its plates, as the two plates hold identical but opposite charge. However, unlike the battery, a capacitor does not generate electrons, and therefore, there is no current flow if the two plates are electrically connected. The electrically connected plates rearrange the charge between them, effectively neutralizing each other.

A naturally occurring phenomenon, lightning, works very similar to a capacitor. The cloud is one of the plates and the earth forms the other. Charge slowly builds-up between the cloud and the earth. When this creates more voltage than the air (the dielectric) can bear, the insulation breakdown causes a flow of charges between the two plates in the form of a bolt of lightning.

As there is only a dielectric between the two plates, a capacitor will block direct current but will allow alternating current to flow within its design parameters. If you hook up a capacitor across the terminals of a battery, there will not be any current flow after the capacitor has charged. However, alternating current or AC signal will flow through, impeded only by the reactance of the capacitor, which depends on the frequency of the signal. As the alternating current fluctuates, it causes the capacitor to charge and discharge, making it appear as if a current is flowing.

Capacitors can dump their charge at high speed, unlike batteries. That makes capacitors eminently suitable for generating a flash for photography. This technique is also used in big lasers to get very bright and instantaneous flashes. Eliminating ripples is another feather in the capacitor’s cap. The capacitor is a good candidate for evening out the voltage by filling in the troughs and absorbing the crests.

# How to solder like a pro

Manual soldering is a skill that gets better with practice. For those who are starting out for the first time, manual soldering can be risky, unless they take proper care and follow safety instructions. Manual soldering involves application of heat locally by a soldering iron, whose tip may reach temperatures as high as 400°C. Soldering materials are sometimes toxic, especially if using lead based solders. Some very useful information about soldering can be found here.

One of the best tips to follow for both starters and experienced people is to don safety glasses before starting to solder. This is something that should become a habit for everyone who is soldering, because hot solder entering the eye can be dangerous. A wire, bent the wrong way, can easily flick hot solder into the air. When cutting a component leg, the cut piece can travel at high speeds. Safety glasses will save the eyes from all these flying missiles.

For most people, soldering skills will not be very good at first, but will certainly improve over time. There is no magic in making perfect solder joints every time, you will simply get used to how to hold things, when the iron is hot enough and the feel for how long you need to apply the heat on.