Electrical Engineering

A coupling capacitor voltage transformer (CCVT) is composed of two stacks of capacitors which step the primary voltage down to a lower voltage potential transformer. These are typically used on 100kV and above, and the potential transformer is often around 15kV on the primary side.

There are two reasons to use CCVTs over PTs (potential transformers) - at the above voltage levels, they are cheaper, and they can be used for power line carrier signal injection.

Under transient conditions, CCVTs typically won't perform as well as PTs, and also may have worse accuracy ratings, so are often not acceptable for metering purposes.

There's very little point in having a distribution transformer if its secondary winding isn't connected to a load! So, to answer your question, a 'secondary system' (by which you, presumably, mean 'load'), isn't 'essential' to a distribution transformer, it could just sit there doing nothing!

Using DC the problem can be electrolytic action in the material being tested that causes the reading to change with time. AC prevents that happening.

A piece of intrinsic (pure) silicon at room temperature has, at any instant, a number of conduction-band (free) electrons bthat are unattached to any atom and are essentially drifting randomly throughout the material. Also, and equal number of holes are created in the valence band when these electrons jump into the conductance band.

Professor Eric Laithwaite of Imperial College, London developed the first full-size working model of the linear induction motor In the late 1940s.

This was the first system which allowed the train to both hover and move using the same motor.

Earlier systems of magnetic propulsion do exist, with or without 'levitating', but Professor Laithwaite was the first person to actually make a full-sized maglev.

This welding machine is useful to melt the metal at the end points. It converts 120-240 volt AC electricity to welding voltage.

Thanks

Artech Welders

• advantage - less ripple, possibly allowing use of less expensive filtering and regulating circuits
• disadvantages - more parts and/or more expensive parts needed in rectifier circuit

Well, if 80kW is your PEAK value, then you need an 80kw generator. If 80kW is your nominal current, you need to figure out what your peak current is. This will depend on the type of load. Is mostly motor loads? If so, your peak current may be significantly more than nominal, depending on the starting sequences of the motors. Clear as mud?

The power circuit begins at the wall. The control circuit comes in over the cable. If you touch the power circuit, you get a shock. If you touch the wire from the cable, nothing happens. The power contains the power to give the light to the television screen. The cable tells it what picture to show. Now, if you look at your Circuit diagram, you will see where the power comes to the computer. It might say +5v or +12v or it could show and input of 110 volts and an output of +5 and +12. There probably is also a -5 and -12 somewhere. Those are your power circuits. They power the entire computer. If you look closely at your wiring diagram, a wire from that goes to every transistor in your computer. The control circuits are likely to go anywhere. They carry data. The power circuits all go back to one point. The control circuits do not.

Potential difference = Current * Resistance

so putting in the values of p.d. and current and finding the value of resistance gives a value of 40 ohms.

When the three phase stator windings are fed by a three phase supply, a magnetic flux of constant magnitude, but rotating at synchronous speed is produced. The flux passes through the air-gap, and cuts the rotor conductors which yet are stationary. Due to the relative speed between the rotating flux and the stationary conductors, an emf is induced. ( Faraday's laws of electromagnetic induction ). Since the rotor bars or conductors form a closed circuit, rotor current is produced whose direction as by the Lenz's law, is such as to oppose the very cause producing it. In this case, the cause which produces the rotor current is the relative velocity between the rotating flux of the stator and the stationary rotor conductors. Hence, to reduce the relative speed, the rotor starts running in the same direction as that of the flux and tries to catch up with the rotating flux.

1.resistance commutation 2.e.m.f commutation

on adding load on a dc shunt motor, the amount of current and torque will increase.

but terminal voltage will decrease

In the metric system, the same units are used for volume, whether you measure liquids, solids, or gases. Commonly used units include the cubic meter, the cubic decimeter (or liter), and the cubic centimeter (or milliliter).

The voltage and current will give the kVA, but the kW depends on the power factor of whatever load is connected to the supply.

For a (let's say) 11 kV supply, the voltage from line to neutral is 11,000/sqrt(3) which is 6351 v. The kVA on each phase is 6.351 times the current, and you just add up the three kVA values to find the total.

At higher voltges like 11 kV the three currents in the lines are usually very nearly equal.

Yes but it's redundant and may cause unnecessary "tripping" of the circuit. The GFCI circuit breaker is intended to protect an entire receptacle circuit whereas a GFCI receptacle is designed to protect only that receptacle and any which are provided power from its load side. (downstream)

Amps are a measure of current flow in an electrical circuit and represent the physical number of electrons passing a point in a circuit per second. 1 Amp of current flowing in a circuit means that every second 6.242 x 10e18 electrons goes past a point on the circuit.

Volts are a measure of how much energy each electron has with reference to another point. A voltage is a difference in energy and has no meaning without a reference point. 1 Volt means that for every 6.022 x 10e23 electrons, there is one joule of electrical energy.

Ohms are units of resistance, how much opposition the conductor provides to the current. Resistance is related to the phyiscal size of the conductor.

These three units relate to each other in Ohm's Law: Voltage = Current x Resistance because if there is more opposition to the current, there needs to be more energy to make it flow.

A common illustraiton of an electrical circuit is a water pipe: Amps is how fast the water is flowing, Voltage between two points is the pressure difference and Ohms describe how big the pipe is and if there is any obstruction inside it.

Some capacitors are polarity sensitive; some are not. It depends on the design. Electrolytic capacitors, for instance, are polarity sensitive, while ceramic disc capacitors are not. You can generally tell, if the capacitor is marked with polarity signs, such as + and -, if it is or not.

Unfortunately, there is no straightforward answer to this question. A cable's current-carrying capacity depends on various factors, including: the number of cores, its type of insulation, whether it's armoured or not, and the method of installation. Depending on these factors, the current-carrying capacity varies from around 14 A to around 21 A, but for specific information, you'll need to check out the appropriate Tables in BS7671:2008 Requirements for Electrical Installations.

DC shunt motor can be reversed by changing the polarity of either the armature coil or the field coil.

Passive components are components that don't require power being applied in order for them to work. A transformer would be considered an active component because it requires power to operate, while a capacitor, resistor and similar items are considered passive, and many perform multiple functions. For instance, a capacitor will pass AC while storing DC, a resistor can be used to limit voltage or current, etc.

A magnetic field is induced by pushing current though a wire; so you could consider a straight wire an electromagnet. Using more coils will strenghten the electromagnet, though, so a straight wire version will be very weak comparitively.

hardware design and implementation. The exact same as the application of a microprocessor. Many modern, high power digital systems are centered around a microprocessor.