0
Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
Why are all cores exposed to ac flux variation laminated?
Limit effects (heat loss) caused by eddy currents
The stator coil is exactly the same as a 3 phase induction motor. The difference being the rotar which has 3 phase wiring in star point or delta connection and also has the sliprings connected to the wiring of the rotor. Brushes are use for the contact between the surpply and the rotor. By controling the current we can control the torgue and speed of the motor. This is done with resistance. Resistance can be greated by means of a resistance bank, liquid resistance or a variable resistance. The basic Idee is: The higher the resistance, low starting current, high torque, high % slip. Motor runs slowly
Low resistance , Higher starting current, lower torgue, lower % slip Motor runs faster.
Thus by varing the rotor resistance the motor can be adapted for a spesific load.
The motor Are mainly used for Overhead cranes, Elevators in buldings, Pumps under pressure and large fans
What is meant by single line diagram?
Single sine diagram is graphical representation of electrical circuit drawn using single line instead of drawing 3 separate lines for three phases.
What are advantages of electronic wattmeter?
The advantages of wattmeter include adequate for low frequencies, easy to operate and better technology. There are different types of wattmeter and each has specific advantages.
What is the demand for engineers?
Job Outlook
Employment of engineers is expected to grow about as fast as the average for all occupations over the next decade, but growth will vary by specialty. Environmental engineers should experience the fastest growth, while civil engineers should see the largest employment increase. Overall job opportunities in engineering are expected to be good.
Overall employment change. Overall engineering employment is expected to grow by 11 percent over the 2006-16 decade, about as fast as the average for all occupations. Engineers have traditionally been concentrated in slower growing or declining manufacturing industries, in which they will continue to be needed to design, build, test, and improve manufactured products. However, increasing employment of engineers in faster growing service industries should generate most of the employment growth. Job outlook varies by engineering specialty.
For the source and more detailed information concerning this subject, click on the related links section indicated below.
How field current change in 'V and inverted v curves ' of synchronous motor?
In v curves armature current decreases in under excitation and increase in overexcitation as fielcurrent increases and armature current is maximum at unity power factor.The power is maximum when load angle is equal to impedance angle.A linear motor is a essentially a multi phase
Why does voltage lead current in an inductor?
From what I've read, an inductor is designed to store energy in the form of a magnetic flux. A simple inductor can be thought of as a coil of wires around a medium. The current causes the flux to go through each turn of the coil. Further examination and Faraday's law leads to this model.
v= N * D(magnetic flux)
Because the current inside the coil is what generates the flux, the voltage will change first, before the flowing electrons will get all the way through the inductor.
The inductance constant L is the Number of turns in the wire times the ratio of the current i to the magnetic flux, which is usually a constant.
L = N*flux/i
Which leads to this relationship between voltage and current in an inductor:
v = L* D(i)
The D() function being a derivative. Because the derivative of the current will change before the current actually does, voltage leads current in an inductor.
What is National Electric Code Article 250?
The national electrical code is a publication thet governs commercial, residential and industrial electrical installations. Article 250 is the section governing grounding and bonding installations.
Why cooling of a transformer is necessary?
TO INCREASE END-OF-LIFE EXPECTANCY OF THE UNIT AND MAXIMIZE CAPACITY AND TO HANDLE OVERLOAD UP TO 40%.
Why are transmission voltages in multiples of 11?
Transmission voltages are in multiples of 11 to allow for 10% transmission line losses. Therefore, to obtain 100% efficiency, voltages in multiples of 11 are transmitted.
A binary encoder is a person who creates a code used to program computers at the most basic level. Claude Shanna developed binary encoding in the 1930s.
How can a CT generate a lethal high voltage when not connected to burden resistance?
A CT is a current transformer. The key word is transformer. Any transformer has a turns ratio. Take a 480V to 120V transformer for instance. The ratio is 4:1, that is for every turn of wire on the secondary winding, there are four windings on the primary. So, if there are 200 turns on the secondary, there are 800 on the primary. We can reverse that same transformer to make it a step-up transformer. Now we would say it has a turns ratio of 1:4. Lets take that transformer and modify it (in our imagination) to see what will happen. Every time, we will apply 120V to the primary, and measure the output voltage on the 800 turn secondary. We will change the number of turns on the primary each time. First, the original ratio: 200T (turns) : 800T (turns) = 1:4 (ratio) = 120V (input) : 480V (output) OK, that seems pretty obvious. But now lets start removing turns from the primary. Watch the trend of secondary voltage: 100T : 800T = 1:8 = 120 : 960 50T : 800T = 1:16 = 120 : 1920 25T : 800T = 1:32 = 120 : 3840 5T : 800T = 1:160 = 120 : 19200 2T : 800T = 1: 400 = 120 : 48000 Wow, the output voltage for our transformer with a two-turn primary is a whopping 48000 volts! Is it possible to have a transformer with a one-turn primary? That is exactly what a current transformer is! the bus wire that passes through the CT forms a one-turn primary, and the many-turn CT coil forms the secondary. If the secondary is shorted, the secondary reflects the primary current divided by the number of secondary turns. But if the CT is open, the current ratio is now 1:zero (no load), the voltage ratio is the inverse - 1:infinity. So, if the CT is not shorted with a very low resistance, it tries to be a voltage transformer with an extremely high secondary voltage. In practice, the voltage is limited by coronal discharge and/or insulation breakdown of the windings. But it can produce some pretty good fireworks and smoke while it is happening! I once observed a facility electrician at one of my customers industrial plants accidentally cut through CT wiring while it was energized. He thought the conduit was abandoned and he was removing it. That CT wiring easily produced an impressive 2-inch continuous arc. This is why CT's are wired through special terminal blocks that short out the CT when the disconnect is pulled. You should never try to work CT wiring hot, and not under any circumstances if you are not trained and qualified!
1000 watts at 220 volts for 2 hours how much energy is used in joulels?
There is no need for the value of 220 volts. Energy E = P · t = 1000 watts times 2 hours = 2 kWh = 7200 kJ 1 kWh = 3 600 000 J = 3 600 kJ For more, look here. Scroll down to related links and look at "Energy Converter".
i dnt no m8, that's what im trying to find out its solid.
What is Infrared reciver tsop 1738?
it is used for reciving the infrared signal of frequency 38khz from a remote location at distance may be 10 m.
What is Uln 2803 relay driver?
The ULN2803 is a small integrated circuit that contains 8 transistor driver channels. Each channel has an input to a resistor connected to the base of a transistor and a 1 amp open collector output capable of handling up to about 30volts (if my memory is correct). Each of the collectors has a reverse biased diode connected to a common Vcc pin that provides inductive spike protection. Typical uses are for micro-processor interfaces to relays, lamps, solenoids and small motors. A 2803 with a set of relays is a simple and effective way of switching mains voltages for example. They are used less commonly today but were once an almost universal means of interfacing processors to power devices.
How much electricity is needed to illuminate 108 square feet of space?
20-40 watts flourescents - depending on how much light you need.110vac @.3- .6 amps
How do you know which way the current is flowing in a circuit?
In metal conductors, current is a flow of electrons. As electrons are negatively charged, they are repulsed by an external negative charge and attracted towards an external positive charge. In other words, electrons travel from negative to positive.
Before the structure of an atom was understood, scientists such as Benjamin Franklin believed that current was a flow of some type of mysterious fluid, which flowed from an area of high pressure, to an area of low pressure. High pressure was considered to be positive, while low pressure was considered to be negative. For this reason, it was believed that current flowed from positive to negative.
To differentiate between these two theories on current flow, we call the modern theory 'electron flow' and we call the older theory 'conventional flow' (or 'Franklinian flow').
Conventional flow was established for such a long time, that a great many (in fact, probably most!) textbooks still continue to use it, even though they know the direction is the wrong way around! In my view, this is unfortunate as it can lead to confusion where there need not be any. Nevertheless, we have to live with it!
In practise, it doesn't really matter which one is used, just so long as it is used consistently. As many of the 'laws' relating to the polarity of electromagnets depend on current direction, when studying magnetism it's very important to determine whether 'electron flow' or 'conventional flow' is being used. For example, Fleming's Left-Hand Rule for conventional flow becomes Fleming's Right-Hand Rule for electron flow!
Why is the tube in the thermometer made very narrow?
To save materials and thus costs of production Umm yeah you are 100% wrong. They are so narrow so that the liquid doesn't slide up and down the thermometer when u take it out of your mouth and try to read it. Adhesion allows the liquid to cling onto the tube which keeps the liquid stationary.
Actually, you're both...mostly wrong. The alcohol/mercury expands when heated. For this reason, the thin tube allows for one to see the change in temperature, whereas a wider tube would result in more subtle and difficult to read changes.
What does the spinning wheel in an electric meter mean?
The spinning wheel spins when electricity is used in the house and the more electricity that is used the faster it will spin. The number of rotations is used to count how much electricity has been used.
When is necessary to change CMOS parameters?
It's simple about that changing the parameter of CMOS.
When you have to install Windows or OS, you have to change CMOS parameters.
Otherwise, you have to change something, such as first boot device and second boot device.
CMOS can perform some function to block the autorun function from USB port.
Thus, your computer may have good security.
And you can also change to control some parameter for your computer's hardware devices, like Fan,temperature and so on...
That's all I remember about that.
Thank you everyone who ask this question.
- Aung Zin Linn (I.D.C.S student, Ygn)
Describe a time when you decided to change your method?
When I found out 20 years ago that all people around me whether at my workplace, friends, neighborhood is practicing and observing NORMS of the society. The result and status of their lives is generally the same (whether a boss or normal employee)but by making a BIG Difference in all facets of my life (of course without breaking the law) -- I can say "NO REGRETS".
