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
Insulators are materials or substances that do not readily allow the passage of sound or heat. Two examples of insulators are glass and porcelain.
What is the different modes of the radio wave propagation?
Ground wave, sky wave and space wave propagation
Answer 1000 RPM or 16.667 HZ, 50 Hz * 60 = 3000 RPM 3000 / 3 = 1000 RPM, or 50 HZ / 20 (1/3 of 50 Hz) * 60 seconds. Or Hz * 20 ( converts to RPM) For 4 pole then, Hz * 30 = RPM For 8 pole, Hz * 15 = RPM
14 cm or 5.5 inches. i have one in my pocket but it won't let me put a picture
How does a 3 phase induction motor continue to run during single phasing?
The magnetic field produced by the powered phase induces a voltage in the other two phases. Such a setup has no rotating field to start the motor, but it will continue to run if already turning. The power output will be less than normal.
This is the principle used in so-called rotary converters, used to run 3-phase equipment from a single phase source.
It does have to be turned on. A highly regulated PS will be the same under load as without a load. But it may not be able to supply the amps. Best connect it and test it. WHO WON?
What is the lumen output of led lamps?
LED light output varies greatly from near-zero to a current maximum of about 400 lumen. It is important to note that the lumen output does not necessarily indicate the potential for a light source to illuminate a surface for the purposes of viewing that surface with the human eye; two lamps putting out 100 lumen may well look to be of different brightness and provide different levels of perceived illumination.
How is the neutral point in a star connection created?
In a distribution transformer's star-connected secondary, the common point of connection is called the 'star point' and is connected to earth. The star point then provides the neutral connection for the transformer secondary, providing a return path for any unbalanced currents due to an unbalanced three-phase load.
This arrangement provides a four-wire distribution system, comprising three line conductors and one neutral conductor (in addition, there are various methods of providing an earth connection to consumers). The line-to-line voltage is called a line voltage (in the UK, 400 V), while a line-to-neutral voltage is called a phase voltage (in the UK, 230 V). The line voltage being 1.732 x phase voltage.
DYn 11 is a Delta HV winding and star lv with theneutral brought out. At primary substations it is usual to have a neutral ct. The ct is a last line of defence operating a standby earth fault relay which opens the lv circuit breaker (11kV). It may have a stage 2 setting in case the lv breaker fails to open which opens the hV side. If there is no local hV breaker it may operate a fault throw switch. This device shorts one phase directly to earth forcing the protection at the remote end to operate.
What are the types of faults in ehv transmission lines?
The three types are
Line to ground faults
line to line fault
double line to ground fault
three phase line to ground fault
a device which output voltage is almost the real peak valueof an applied signal
Stateflow model of a elevator for multi-storied building?
find an example of this model at:
http://www.mathworks.com/help/stateflow/examples/modeling-an-elevator-system-using-atomic-subcharts.html
Learn about the latest that Stateflow has to offer for modeling control logic using state machine and flow chart constructs at this page:
http://www.mathworks.com/products/stateflow/whatsnew.html
Learn more about Stateflow at:
http://www.mathworks.com/products/stateflow/
What is the standard value of lube oil test parameter for a gas engine say 1145 kw?
Viscosity should be within +/- 10% of original value (i.e. no lower than 40cSt for a 46cSt lube oil product)
Water is usually done with a crackling test the result should be negative.
Suggested limits for additives and wear metals (sodium, copper etc) can be found at www.vibronurse.com just check out the lube oil section.
For good long term running particle count should correspond to 4 using NAS-1638 standard. Vibronurse provides a free tool for converting between ISO4406 - NAS-1638 - SAE Grade and actual particle numbers (http://www.vibronurse.com/particles.html).
Does your body allow electricity to flow through it?
Yes of course,
we have salts, minerals etc....
so they do
The body is not a great conductor, but it can conduct electricity and that is why you can feel a shock through static electricity or a killing shock such as an electric chair. Conductance will vary from person to person and will change depending on conditions such as sweat, being wet from a shower and so forth.
Difference between static and dynamic charercteristic of motor?
I think you are talking about the study of the electrical system for motor starting in ETAP (or any such software). Here are the answers:
1. When do we use Static and Dynamic motor starting?
If you know the Motor torque characteristics, Load torque characteristics and the inertia information of the motors, bearings and loads, you can do the Dynamic motor starting study. Otherwise, do the Static motor starting study - it simply needs the starting time and the locked rotor current of the motor.
2. What is the difference between the two?
(1) The Dynamic motor starting develops the motor starting current characteristics based on the motor starting torque, load torque and the inertia, while the starting current remains flat at locked rotor current during the starting time for Static acceleration. (See the previous posting http://cr4.globalspec.com/thread/42981 , comment # 2 for detail how the starting time is calculated for Dynamic acceleration).
(2) Dynamic starting acceleration requires additional data than the Static acceleration.
(3) The Dynamic acceleration calculates the acceleration time and current from the input data, while the Static acceleration assumes you know the starting time and current.
(4) For Dynamic acceleration, the starting current is not 100% flat during the starting time, but in Static acceleration it is flat.
(5) Static acceleration is simple, Dynamic acceleration is rather complicated.
3. Can we evaluate the system using Static only not dynamic?
Yes. Make sure you have the correct information for motor locked rotor current and the stating time for the load.
Go the ETAP tutorial site (http://www.etap.com/training/tutorials-training-videos.htm) and see the tutorial #12 (Dynamic Acceleration) and #13 (Static acceleration).
curtesy msamd
Why are some transformers oil filled?
Transformer oil, or insulating oil, is usually a highly-refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers, some types of high voltage capacitors, fluorescent lamp ballasts, and some types of high voltage switches and circuit breakers. Its functions are to insulate, suppress corona and arcing, and to serve as a coolant.
After Transformer oil is used for a long-period, the oil will turn to dark liquid. The Transformer plays an important role in the generation, transmission and distribution of electrical energy. Under load the transformer, dissipates heat and the insulating oil acts as a coolant as well as an effective dielectric.
Due to the highly hygroscopic nature of the transformer oil, it absorbs moisture from windings, which leads to gradual deterioration of dielectric strength. Also there are some waste impurities, gas contents in the transformer oil which destroy the oil's quality.
Hi-tech Vacuum Transformer Oil Purification Systems is the most efficient and economical purification system.
Hi-tech Vacuum Transformer Oil Purification Systems is applied to filter various of unqualified insulation oils including aging transformer oil specially for the power which is above 110KV, mutual inductor oil, switch oil and so on. Also it can inject the insulating oil into the transformers on-line.
Hi-tech Vacuum Transformer Oil Purification Systems has the great abilities in removing impurities, particles, water content, gas content, acid, etc... making the waste transformer oil to be regenerated to new oil's quality for reuse.
for more information, welcome to visit http://bestoilpurifier.bossgoo.com , or email us kevinnchiang@gmail.com
All the polution problems caused by waste oil will be solved by Hi-tech Vacuum Transformer Oil Purification Systems.
1.kettle element
2.wood
3.plastic
4.glass
5.metal
6.rubber
7.paper
8.diamond
9.silicon
10.plants
What is a Programmable unijunction transistor?
PUT: programmable unijunction transistor It is a device like the thyristor only the gate is connected to the N type material near the anode. It is usually used in time delay, logic and SCR trigger circuits In the PUT, Gate is always positively biased w.r.t cathode. When anode voltage exceeds the gate voltage by about 0.7 V, first junction that is the junction right after the anode gets forward biased and PUT turns on. When anode voltage becomes less than the gate voltage, PUT is turned off.
How do you increase amperage output of solar panels?
1. ADD SOLAR PANEL COLLECTORS 2. ADD MORE STATION BATTERIES 3. REPLACE CHARGER OR ADD CHARGERS ACCORDING TO UPGRADE.
What is a current measured in?
Ammeters (amps)
An Ammeter is a meter for measuring electrical current, the unit of which is the Ampere (amp)
What is a magnet created when electric current flows through a coil of wire?
A magnet created when electric current flows through a coil of wire is called an electromagnet.
How can a tuned RC circuit improve the power factor of an inductive motor circuit?
The RC circuit can reduce the phase shift between the voltage and current in the power line. The phase shift is caused by the inductance of the motor. The phase shift between the voltage and current in the power line causes problems due to the presence of so called imaginary current or power that does no work but must be supplied by the power source.
What is meant by CREE LED Torches?
A CREE LED torch is like a normal battery powered torch, only using some newer features. The most important is the LED (Light Emitting Diode) invented by a American company named CREE. CREE LED's are mostly known for their efficiency. They are normally around 5 times more efficient then a Halogen light of the same spec.
