Electrical Engineering

Leading and lagging currents are not so much "currents" as they are "situations" or "conditions" in an electrical circuit. Reactive characteristics, if there are any, will not let voltage and current be in phase in a circuit. (Unless they are equal, and this will be true at only one frequency.) In some circuits, current leads voltage (or voltage lags current), and in other circuits, current lags voltage (voltage leads current), depending on the circuit and also on the frequency of the applied signal. In a capacitor, current leads voltage, and in an inductor, current lags voltage. This carries over to circuits that exhibit primarily capacitive or inductive characteristics. Additionally, reactance varies with frequency. As a given circuit with inductance and capacitance is evaluated, at some frequencies, it will appear capacitive, and current will lead voltage. At other frequencies, the circuit will appear inductive, and current will lag voltage. Only at a frequency where the reactances are equal will the current and voltage be in phase. The ideas here are best reviewed after achieving an understanding of the nature of inductance and capacitance, the associated reactances, and the way frequency affects these characteristics.

There is no such thing as an 'induced current'. What is 'induced' is a voltage. The direction of the induced voltage is determined by the direction of the changing current that induces that voltage, because the induced voltage will always act to oppose that change in current. So, if the current is increasing, then the direction of the induced voltage will act to opposethe increase in current. If the current is decreasing, then the direction of the induced voltage will act to sustainthat current.

Vanguard, Tettex, AEMC are major ones for transformer market.

An ampere-foot is a unit used in calculating the fall of pressure in distributing electrical mains, equivalent to a current of one ampere flowing through one foot of conductor.

Yes. Where conductors are used at radio frequencies, a 'skin effect' is thought to take place, and often the conductors are plated with silver, which has a higher conductivity than copper.

Another more common example is in electronic plugs and sockets, where the pins are often plated with gold, so as to minimize contact resistance. Gold is unreactive, and this gold plating offers little hold for corrosion that would otherwise interfere with the passage of electrical signals.

A third example would be in high voltage transmission lines, where a steel core is used for strength, and this is given a wrapping of aluminum sheathing. This is not true plating, but gives higher conductivity for a given span which would otherwise be limited by the breaking strain if aluminum alone. .

You will need a phase converter. Avaliable at an industrial supply company like granger supply

Hi,

First understand one thing seriously!! The transformer only can be rated in KVA.

Bcoz, its power factor not depends on the load connected.

I already have the graph drawn on graph paper with 2 waves on , my phase shift is 1.5 and 180degrees.

Anyone know how to add and subtract the sinusoidal ac waveforms on the graph, and by phasor diagram?

There are different kinds of trimmer capacitors, but the most common type is made from interleaved layers of metal and Mylar (or some kind of plastic) with a screw that allow the layers to be tightened together, increasing capacitance as needed. Alternate layers of metal are connected to each terminal, basically making a meshed plate capacitor, where the distance between plates is controlled by the screw.

1. If you don't understand how electricity can kill you, don't mess with it.
2. Always turn off the source of power before working with any electric device or wiring.
3. Use a test meter to verify power has been turned off before working on any electrical device or wiring.
4. Always ensure that any breakers or fuses protecting a circuit limit current to the specified value of wiring and devices connected to the circuit.
5. Ensure all electrical devices are properly grounded.

p=r*i

AVR stands for automatic voltage regulator.

zero volatge regulation means the terminal volatge of transformer at full load on a given power factor become equal to the rated teriminal volatge of transformer , it happens only for leading power factor in transformer

It sounds like you are talking about a band-pass filter. The transistor would be part of a circuit that detects and allows certain frequencies to pass through it. These are used in signal processing circuitry, particularly audio equipment. This is how equalizers work, 'Bass', 'Treble', 'Mid' knobs. a pass transistor has nothing to do with frequency . by definition it will pass the heavier currents of a regulator.for instance therefore the term pass.

Please consult some book.

4

If the bulbs and fans are designed to run on different voltages, then we'd have to know

what the rated operating voltage of each item is, and then arrange them cleverly.

If all of the bulbs and fans are 117VAC units ... each one could be individually plugged into

a household outlet ... then combining them is easy:

-- Connect one end of each bulb, one end of each fan, and one side of the electric cord

all together. Cover the blob of six wires with insulating electrical tape.

-- Connect the second end of each bulb, the second end of each fan, and the second side

of the electric cord all together. Cover this second blob of six wires with insulating tape.

-- Plug the electric cord into a standard household outlet. Each bulb and fan should

operate normally.

Total resistance (thevinen resistance) = 4 + 8

Total voltage = 12 volts.

Ohms law: I = V / R

Therefore I = 12/12 = 1 amp.

By using C-filter

A ring-main unit is a piece of switchgear used on high-voltage distribution ring-main systems (e.g. in the UK at 11 kV). Essentially, it's three switches incorporated into one device used to connect a transformer to a high-voltage ring main. It allows the transformer to be connected/disconnected to the ring main and it also allows the ring main to be 'broken'. Each of the switches has three positions: open, closed, or earthed (grounded); the earth position allows the transformer or either (or both) halves of the ring main to be earthed when maintenance is required.

A three-phase transformer bank is often used in power stations because it is easier to construct and transport very large single-phase transformers, compared with constructing and transforming an equivalent-capacity three-phase transformer.

Measure the current and voltage on the secondary side.