A kilowatt is an unit of true power in an AC circuit -as measured by a wattmeter.
A kilovolt ampere is an unit of apparent power in an AC circuit, which is the product of the voltage across a load by the current through it.
The relationship between the two is: kilowatt = (kilovolt ampere) x (power factor of load)
In insulators the bond energy between atoms in the material they form is very high. We need to give large energy to overcome that bond energy and set free the electrons.
As electrons are not freely available It doesnt conduct well.
There's a kind of circularity in the question. Anything that doesn't conduct electricity for any reason is called an insulator. So any substance where the electrons are too tightly bound to atoms and cannot migrate is called an insulator. Anything that manages to let electrons migrate wouldn't be called an insulator.
if electrical panel is labeled LT, usually means its a lighting panel
LT means "Low Tension" panel. Not lighting.
Lighting panels are normally known as LDB (lighting Distribution boards)
The watt is defined as 'the power resulting when one joule of energy is dissipated in one second'.
If the cable is a 4 wire change the male and female ends to a 3 phase 480 with ground plug and receptacle
Diagrams are unavailable in this Q & A format.
A good diagram source is Sq D Wiring diagrams, see sources and related links below. This book has a wealth of information for anyone that does electrical control work.
Yes. It will draw approximately 5% more current than it would at 460 volts for the same power output.
None of those materials will conduct electricity. They are therefore called insulators. However if a sufficiently high voltage is applied across an insulator it is possible that it will be damaged. This is known as the "breakdown voltage". The amount of voltage needed to cause breakdown depends mainly on its physical and chemical composition and partly on its actual thickness. For the materials stated - and provided that their surfaces are not damp or wet - the breakdown voltage is probably many thousands of volts. As can be imagined, when an insulator breaks down there will most probably be a flash of light, a loud bang and lots of smoke, maybe even a fire, so these kinds of things can only be tested safely in a properly equipped lab or maybe at your local Fire Station! The speed of electric travel thru a 'paper' capacitor or a 'plastic' capacitor is about the same (not familiar with a 'yarn' capacitor?). The main differences are the dielectric strengths of the materials which means HOW THICK do the materials have to be before the electricity will break thru it. If you meant to ask what the wire covering (yes, wire used to be covered with yarn!) does to the speed, the covering has no affect on speed.
In today's culture, electricity is a vital part of functioning as a society. Simple tasks, such as waking up at a designated time or enjoying a piece of music, are accomplished currently via electronic means. One only needs to consider the consequences of a relatively short power outage factories close down, phones and computers go dead, traffic slows to a crawl, food spoils in refrigerators to accurately observe how power-dependent our society has become. However, electricity is a constantly developing technology, and the aspects one currently associates with electricity and electricity generation are nowhere close to the original features. In the past century and a half, electricity has steadily evolved from a scientific curiosity, to a luxury of the affluent, to a modern need. Along the way, it has been shaped by a variety of non-technological factors: economic, political, social, and environmental, to name a few.
Electrical manometer is an electronic manometer use to record pressures between two points. It is commonly used in recording pressure in bridges.
In general, a DCS or PLC, handles numerous discrete I/Os. One common I/O module (board) is used to supply 8, 16 or more points. Discrete output circuits from a DCS typically use low power level signals (transistors, micro relays) which cannot be sent directly to the field devices such as electromagnetic valves or motor control circuits. That is why interposing relays are often necessary.
These relays play an important role by amplifying the current capacity of the contact signal of the I/O module allowing larger current flow. In addition, discrete input circuits normally can handle only dry contacts or wet contacts of low voltage, which also require interposing relays.
For example, let's say the relay of a PLC can only accommodate 0.5A at 220 VAC, but the solenoid which is to be connected to the relay requires 1.2A at 220 VAC. In this case, an interposing relay with contacts rated for operation at 1.2A at 220 VAC would be used as an interposing relay "between" the PLC relay and the solenoid. The coil of the interposing relay should require less voltage and current than the driving relay is rated for, and the contacts of the interposing relay must be rated to handle the requirements of the load (solenoid, light, contactor, motor, etc.).
Its circuit. But this is hard to marry with lightning, which is the path of an electric current.
1. Describe the electrical systems you have worked on and how did you get your training?
2. What is your experience with electrical schematics?
3. What is your experience with ladder logic?
4. Describe the malfunctions you have experienced with PLC hardware?
5. Describe a tough electrical troubleshooting problem you have experienced, and briefly explain the steps you used to solve the problem.
6. What is the difference between a digital signal and an analog signal?
7. How often do you use a personal computer in a typical day? What do you do with it?
8. Describe a process problem you have experienced and how did you solve it?
9. Give an example of a tough loop you had to tune. What were the problems? And how did you solve them?
10. What brands of VFD's are you familiar with.
11. Describe some of the malfunctions associated with VFD's, and give an example of a tough VFD problem you had to solve.
12a. Using Ladder logic, write a program that will START and STOP a motor with momentary START and STOP push buttons. (Provide a sheet of paper)
12b. Add ladder logic that will turn the motor OFF after running for two minutes.
13. Describe the steps you take to troubleshoot a 3 phase, 480 volt motor that continually trips the heaters.
14a. Why is the earth pin in a 3-pin plug the longest and the thickest?
14b. Explain the purpose of grounding.
15. Describe a control panel you wired, designed, or modified. What was the purpose of the panel and state each component you used.
16. Describe the difference between a sourcing input and a sinking input.
17. Why do you want this job?
PWR 1)sensitivity of ELCB
PWR 2)about MCB ratings
PWR 3)earth resistance and earth compounds
PWR 4)what is LDR
PWR 5)your electrical activity in your society
PWR 5)CONSTRUCTION OF CAPACITOR
PWR 6)transformer and related formulas
PWR 7)industrial lightings
PWR 8)what is the nature of electrons
PWR 9)use of ballast in tube light
PWR 10)CABLE SIZE AND AMPERE RATINGS
The best way to improve power factor is by adding capacitors. Low power factor is due to reactive loads (motors, pumps, etc.) that are connected to your electrical system.
The best way to improve power factor in the case of motors is to use a motor drive, like a Variable Frequency Drive. These drives allow very precise control over a motor, unlike the very sudden, jerky starting and stopping across the line seen when using a motor starter. They eliminate the huge inrush current required to start motors that causes low PF.Answer:
1) Power factor can be calculated by connecting an energy meter [P] (voltage coil in parallel & current coil in series with the load), a voltmeter [V] across load and an ammeter [A] in series with the load. Measure P, V & I.
Since, Active Power (P) = V.I.Cosϕ
power factor = Cosϕ = P/VI
2) Power factor is usually (industrially) improved by connecting a shunt (parallel) capacitor bank at feeding end.
How it works??
Inductive loads contain both inductors and resistors. But due to phasor difference of coils and caps when voltage is applied across both, the two currents results in a smaller net current finally. So now the angle (ϕ) between the voltage phasor and current phasor is lessened. When ϕ is reduced, Cosϕ is risen resulting in a higher power factor.
This is a very broad question. Every aspect of daily life was changed by the electric lightbulb and all the electrical products that followed.
The electric streetlight was one of the first community-wide improvements to cities and towns. This increased safety and reduced crimes.
Home and Fire Safety
All homes used oil lamps or candles and most homes heated with coal and wood. Each brought fire risks in mostly wood-frame homes. Candles and lamps could easily tip over, causing fires. Sparks from fireplaces jumped protective grates.
Overheating (overfiring) of coal/wood stoves and furnaces caused numerous housefires, including through the 1970s in some areas.
Electric and gas driven furnaces reduced individual and family labor by a good 99% since they no longer had to obtain coal/wood, build a coal/wood fire, continually check on the fire, etc. As well, the house or building could stay at one consistent temperature, give or take a couple degrees. However, with wood-coal furnaces, fires went out during the night, the fire needed re-built in the morning, and it took longer to re-heat from a very cold inside temperature.
Convenience leads to personal freedom, more leisure
Women, especially, benefitted by electric power since women did most household duties. Instead of handwashing or using a manual ringer washer (which often caused injuries), washers freed women from heavy labor. Instead of hanging clothing outside to dry (although some people still prefer naturally-dried clothing), electric dryers saved time and manual labor.
Gas and electric stoves and ovens freed men and women from having to lug coal to the cook stove. Both newer stoves meant less baking times, and less fire risks with cooking.
See above about gas / electric furnances.
With electricity, people had more options for day, evening, and night leisure activities. Theaters and playhouses could start a show in the evening rather than just having afternoon shows. Stores could stay open longer, resulting in increased shopping and convenience. Amusement parks and circus type shows, rather than oil lamps, could add machinery ... and evenually park rides.
In many areas, electric-run streetcars replaced horse and buggy or the most common 'transportation'-- walking.
These are just some of the ways that electricity permanently changed daily life and influenced the development of more personal products and led to vast changes in industry.
The new headquarters will now be in Cranberry, PA. Approx 40 Minutes north of Pittsburgh
Just swapping the hot and neutral connections on a plain and simple single phase ac motor (one which was not designed to be reversible) is usually a waste of time as the voltage is alternating and the motor sees this as the same either way and it will still run in the same direction.
For a DC motor which uses a permanent magnet to provide its magnetic field, simply switch the two power leads to make them run in the reverse direction.
For a DC motor which has a wound field winding instead of a permanent magnet you have to reverse the connections either to the field winding or to the armature. (If you reverse the connections to both the field winding and the armature the direction won't change!)
For a three phase motor simply switch any two of the three power leads to make it reverse.
To change the direction in a single phase ac electric motor you must find a way to reverse the connections to the field magnet (outer windings) or to the armature or rotor (which is the center part that spins). Some motors are reversible and the run direction can be changed simply by swapping the 2 plugs sticking out of them that are connected to the field windings.
All single phase ac motors can be reversed by physically reversing the field magnet or rotor ( front of motor is now the back) although this can be more difficult in motors with brushes because of the brush holder which is mounted at the front and usually has to stay in the front.
Changing motor rotation
A split phase induction motor has two sets of coils and a centrifugal start switch. The start winding is in series with the start switch. The start winding provides a rotating magnetic field in one direction enabling the motor to start. The motor can be reversed by reversing the connections of either the start winding or the run winding but not both.
Whichever way it is connected, no matter whether it is in a star configuration or in a delta configuration, a 3-phase motor's start-up current can be more than 4 times its normal running current.
If the star configuration is used when first switching-on power to a 3-phase motor, a much smaller "start-up surge" is forced onto the power lines than if it were switched-on directly in the delta configuration.
So "using star for start-up" achieves very worthwhile purchase cost savings because smaller circuit breakers and thinner 3-phase line wire sizes can be installed to supply power to the motor.
However, leaving it running in star has a major disadvantage: the motor can never deliver as much power and torque as when it is running in delta.
For that reason a 3-phase motor was usually started in star mode and then - after reaching a steady speed - switched over to run in delta mode to achieve its maximum power output.
The explanation for this is easier to understand if you draw a sketch of the wirings and their connections, but unfortunately we cannot use diagrams when giving an answer here! Anyway, if you draw the circuit diagram for the windings connected in a "star" or "Y" configuration, it should look like a three-pointed star, with a phase input power line attached to each point of the star.
Thus, when a 3-phase motor's three windings are connected in a star configuration, the current from each individual phase power input line goes directly into one winding and is then series-connected to both of the other two windings via the star's "center-point".
If you draw the circuit diagram for a delta configuration, it should look like a triangle with a phase power input line attached to each point of the triangle.
Thus, when a 3-phase motor's three windings are connected in a delta configuration, each winding is effectively connected directly to two phase supply lines. The third phase supply line is also connected to that winding, but indirectly via the other two windings. They are connected in series to one another, and that series pair is connected in parallel across the first winding, to form the "delta".
The much lower starting current is the main reason why a three-phase motor was usually started in star mode and then - after gaining a steady speed - was switched over to run in delta mode to achieve its maximum power output.
Update: Electronic motor-control systems, which offer soft-starts in DELTA configuration, are now replacing the use of manual or semi-automatic star-delta starters.
When the windings of a 3-phase motor are connected in STAR:
the total output power when the motor is connected in STAR is:
PS = [VL x (1/.'/'3)] x [ID x (1/.'/'3 )] = PD x (1/3) [one third of the power in DELTA]
VL is the line-to-line voltage of the incoming 3-phase power service
ID is the line current drawn in DELTA
PS is the total power the motor can produce when running in STAR
PD is the total power it can produce when running in DELTA.
For more information please see the answers to the Related Questions shown below.
It is the installation of ground rods at a service entrance distribution to bring the relative resistance to ground to be within 5 ohms of the utility's distribution network. This grounding system is then connected to the service distribution with a calculated size wire and connected to the distribution at a point within the distribution panel, where the service neutral wire joins the neutral bus bar.
The use of a star delta starting is determined by the horsepower of the motor. It is the utility company that has to be asked - What is their policy on how much horsepower will they allow for across the line starting. These days pump installations usually opt for VFD controllers. This will allow the pump to ramp up to speed and ramp down in speed to stop. Using variable frequency drives totally eliminates water hammer from harming the water system. The extra cost of the VFD's is more that offset by eliminating the expensive equipment that is used to prevent water hammer.
you would wire a float switch into the control circuit i.e, the contactor coil (which is relatively low current but rated at least for the control voltage,, in most cases 120VAC). also in the same circuit would be the overload contacts. if the overload trips and/or the float switch opens then voltage is removed from the contactor coil
As well as motors, contactors also have kW and Ampere ratings. Have a look on the name plate of your motor and you will see its maximum current draw (amps). Select a contactor with a current rating greater than this.
What you are looking at is a two pole 100 amp breaker. Distribution panels in North America are designed to use 120/240 volts. Any two adjacent breakers will give you a 240 volt circuit and either leg to the neutral will give you 120 volts.
On the main breaker of a panel the number stated on the breaker is the amount of amperage that the breaker will allow to pass before tripping regardless of which leg the current passes through.
A 200 amp service will have a two pole main breaker with a rating stating its capacity of 200 amps.
Wire size into the breaker will give you a good clue as 100 amp breakers will use a #3 conductor whereas a 200 amp breaker will be fed with a 3/0 conductor.
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