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Electrical Engineering
Electrical engineering is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism.
23,056 Questions
What will happen if 60hz rated appliance is supplied with 50hz supply?
Almost every appliance has a range of use that appliance if you use between that range, you are safe, but if you use the appliance in above or less frequencies it may be harmful for you like circuit fire.
How do you stop transformer hum?
1. THE INSULATION IS DETERIORATING
2. LOOSE TERMINATIONS
3. NO RUBBER FOOTING INSTALLED
4. OVERLOADING / UNBALANCED LOADING
5. Magnetostriction. When the core becomes magnetised, it expands, then it contracts and expands again as the field is reversed. A 50Hz transformer therefore expands and contracts at 100Hz, producing a sound at that frequency.
As more lamps are put into a series circuit what happens to the overall current in the circuit?
The more lamps you add, the dimmer each would become. The brightness would be the same for each lamp -providing they are all the same wattage. If one of the lamps wasn't working, then none of them would work. If the wattage of the lamps varied, the brightest lamps would be those with the lower wattage rating (yes, this is not a mistake!).
Lamps in series can be dangerous if one isn't working, because the full circuit voltage would appear across the open terminal.
Why are control panels used in substation?
Substation is the place (in transmission of power with overhead/underground cable) where the voltage level may be increased or decreased. That voltage level is so high that any personnel on its own cannot check/handle it by meters physically. Also the load on the system is never constant so there are fluctuations (ups/downs) in all the parameters of the electricity, like voltage, current, power factor (reactive and active power), frequency etc. So to calculate/estimate those things continuously with the time we need to implement separate monitors for them. This also implies that if any unacceptable change is observed in the power system, it should be immediately solved and continuity of power should be kept. That is the reason we go for control panels in substation.
Now in control panels there are all the those things which are required for the measurement of voltage, current total power, frequency, power factor. These are measured at all time of the day. If any fault is observed in the measured readings, then it is cleared immediately, and if it is not able to clear it itself, then the personnel on the substation can clear it by switching off the certain power line through circuit breakers. CBs, relays, CTs, PTs, APFC all are incorporated in control panels.
If still you are not clear with what is mentioned above, please feel free to ask me on dishant22@hotmail.com
Lighting contactors how do they generally work?
Lighting contactors are electromechanical devices used to control large lighting loads, typically in commercial or industrial settings. They operate by using an electromagnetic coil to open or close a set of contacts, allowing or interrupting the flow of electricity to the lighting circuit. When the coil is energized, it attracts a movable armature that closes the contacts, turning the lights on; when de-energized, the contacts open, turning the lights off. This allows for remote control and automation of lighting systems, often integrated with timers, sensors, or control panels.
Low voltage cable size calculation formula?
1) determine load /design current. eg 13kw oven Ib=13000W/230V if 3 phase- 13000w/1.73*400V =56.52A In(circuit breaker size)=60A 2) In/ C1+C2+C3 (c is coefficient of ambience temperature of type of cable referred to BS tables) 3) value of above refer to BS tables for appropiate cale size. eg. based on 60A cable size is 16mm2 pvc/pvc cable size
How many kw electricity can you use on a single phase system?
In common everyday usage and in about 99% of the circuits you will work with, KW and KVA are the same value. However, Watts has a very technical definition that does not exist in every circuit, such as motors, transformers, and capacitors, but every circuit has volt-amps, or VA. The K just stands for thousands in both abbreviations.
More Information:
VA is short for Volt-Amps, i.e. volts times amps, which may seem to be the same as watts. This is true only for resistive loads, where the phase angle of volts is the same as that of amps. In that case KVA is the same as KW.
What happens with non-resistive or reactive loads, however, is that amps are not in phase with volts. In an inductive load, such as a motor, amps lags volts; while in a capacitive load, amps leads volts. In both of these cases, you cannot just multiply volts and amps to get watts, due to a phenomenon known as power factor; power factor being the ratio of apparent power to true power.
To visualize this, you need to draw the power circle. Since WikiAnswers does not presently support graphic images, please take a piece of paper and follow along with me...
Draw a circle. To make it easy to do the math, draw it centered at the origin, and pretend that it has radius of one. This way, the trigonometry is easy.
Consider that the radius of the circle is VA, KVA, or MVA, what ever scaling factor you want. (Do not confuse this with the trigonometry trick where we also consider the radius to be one.)
Now, pick a point on the circle. Twelve O'Clock is a purely resistive load, where volts and amps are in phase. Nine O'Clock is a purely inductive load, where amps lags volts by 90 degrees. Three O'Clock is a purely capacitive load, where amps leads volts by 90 degrees. In "normal" trigonometry, zero degrees is at 3:00 O'Clock, but, by convention, zero degrees when dealing with reactive power is accepted to be 12:00 O'Clock. Just keep the trigonometric identities straight in your mind.
In practice, with normal electric motors and all other things considered, we see a point on the circle at about 10:30 or 11:00 O'Clock. Let's pick 10:30, to make the math easy. So, draw a line from the origin to the upper left at an angle of 45 degrees with respect to the Y-Axis. Label this line KVA.
Notice that KVA is constant, no matter what the phase angle may be.
Now, draw two more lines; one from the point on the circle at 10:30 O'Clock straight down, perpendicular to and stopping at the X-Axis - label this line KW, and one from that same point to the right, perpendicular and stopping at the Y-Axis - label this line KVAR.
Label the angle of the first line with respect to the Y-Axis as phase angle. Positive meaning inductive, and negative meaning capacitive. Notice that, if you had a 45 degree capacitive load, intersecting at 1:30 O'Clock, the magnitude of the KVAR line would be the same, though positive instead of negative, and the KW line would still be the same.
Now, power factor is KW / KVA, the ratio of apparent versus true. In this case, since we picked 45 degrees as the phase angle - to make it easy - the ratio is 0.707, or the cosine of the phase angle.
A typical power meter will register less than the actual power. In the worst case of a purely inductive load, the power meter would register zero, though the KVA is still what it always was. The power meter is "lying", due to the power factor - energy is still being transferred - and the equipment must be sized to handle it - that is why transformers and other things are often rated in KVA instead of KW.
Now, if you are interested, and most power companies, engineers, and electricians are, then look at KVAR. That is kilo volts-amps reactive. There is a KVAR power factor as well, simply the sine of the phase angle. In this case, again with 45 degrees, it is the same as the normal power factor, 0.707, however, we normally would call that -0.707, to differentiate between KVAR (inductive) and KVAR (capacitive).
So, to answer the original question, "How do you convert KW to KVA", you simply divide by power factor, and to obtain that, you need to know the phase angle. It is simple trigonometry from there.
Note that, if your phase angle is more than plus or minus 90 degrees, we are actually talking about a generator, instead of a load.
In practice, the phase angle is more like 20 to 30 degrees, so the power factor would be slightly higher, and the reactive power factor would be slightly lower. Power companies penalize large customers for poor power factors by measuring it and compensating their power meters or accounts to consider the perceived loss in energy or, more correctly, the increase in actual energy use. Also, poor power factor causes degradation of voltage on power lines, so power companies compensate with capacitor banks, shifting the phase angle back closer to zero.
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There is no longer a need to penalize large customers for poor power factors since their billing is based on current, not Watts. This is why you see a very residential-looking meter on the side of very large buildings. There is a current transformer (CT) placed around each service conductor. Each CT is then wired with very small conductors into the current meter. Next time you go through a drive-through, notice the meter location on the back of the building. You will find it in close proximity to a junction box that contains the service conductors.
A current transformer is nothing more than a larger version of a clamp-type ammeter used by electricians.
Can you please explain what RMS value is?
RMS stands for Root Mean Square. It is a method of averaging where you take the squares of a bunch of samples, average them with an ordinary mean, and then take the square root. This gives greater weight to larger values. In the case of an ordinary sine wave, the RMS value is 0.707 times the peak value, 0.707 being 1/2 the square root of 2, and the peak value being one half the peak-to-peak value. For example, in the US, a "standard" 117VAC line voltage is actually an RMS voltage that corresponds to a peak voltage of 166VAC.
RMS is a necessary unit because, often, the waveform is not sinusoidal, it is sawtooth, such as in a power supply. Using an ordinary VOM, calibrated for a sinusoidal AC scale in such a case, will give an inaccurate reading of ripple voltage. Most modern DMM's have a true-RMS mode which will work correctly by using sampling and analysis technology.
RMS is also a necessary unit because RMS is a better indication of how much power a signal can impart to a load.
Another answer
RMS stands for Root Mean Square value.
In electrical technology, where alternating current (AC) is used, RMS Voltage and RMS Current (Amps) must be used to calculate the average power supplied or consumed. See the link below on how to find the RMS.
In fluid flow technology related to gases, velocity is calculated as an RMS value because it can be used to find the average velocity of an ideal gas.
Yet Another AnswerBecause a AC current is continuously varying in both magnitude and direction, it's necessary to measure it in a meaningful way. The rms-value of an AC current is equivalent to the value of DC current necessary to do exactly the same amount of work. For example, a sinusoidal AC current which peaks at 100 A has an rms-value of 70.7 A, and does exactly the same amount of work as a DC current of 70.7 A.
Equation for electrical power?
Google 'Ohms Law'
AnswerOhm's Law has nothing whatsoever to do with power.
The fundamental equation for power in a d.c. system is: P = E I (where P = power, E = supply voltage, and I = load current). From this equation, two others can be derived: P = I2R and P = E2/R, where R = resistance.
For a.c. systems, the fundamental equation must be multiplied by the load's power factor (cosine of the phase angle).
How control the reverspower for diesel generator?
I guess you're thinking that reverse power is a generation error, but it is a change in flow direction. When two generator are running in parallel nd of sudden a generator2 prime is dropped nd due to circuit breaker2 is still in on state Gen2 draws power from Gen1 and acts as a motor. this action will damage the prime mover(engine) nd AVR too. Of course upto 10 amp of reverse current is allowed into a generator as of considering as back emf (while running as generator). So in order to stop thing reverse power, a relay is used which senses the directional flow of power nd immediately turns off the circuit breaker of off prime mover unmatched droop also develops this reverse power flow because of change in voltage nd load sharing
If increase load of secondary side of transformer. why primary side current increases?
The wattage must remain equal on the primary and secondary sides of a transformer. An example to the above statement with a 1000 watt step down transformer. To fine the watts (load) the formula is W = A x V. The primary side of the transformer has the capacity of 1000 W = 4.16 Amps x 240 Volts. The secondary side of the transformer has the capacity of 1000 W = 8.3 Amps x 120 Volts. Using the transformer to its maximum, without overloading it, the primary will be 4.16 amps at 240 volts and the secondary will be 8.33 at 120 volts. As you can see the wattage (load) remains constant only the voltages and current change.
What is the starting sequence of a star-delta starter?
This is the schematic for the starter. K1T is a timer. Initially KM1 and KM3 are closed to start the motor. Then KM2 is closed and KM1 is opened to run the motor This is the equivalent ladder logic using relays and timers.
What happens to insulation resistance when increasing cable length?
The insulation resistance remains the same throughout the entire length of the conductor.
How you differentiate amplifier and transformer?
A big difference. A transformer converts power into more useful means of transportation or matching to the end results.
Pincoming = IPVP = Poutgoing = ISVS.
giving the ideal transformer equation
Vs/VP= Ns/NP=IP/Is
then as the outgoing voltage of the transformer increase, the outgoing current will decrease. An amplifier adds power. For example, voltage amplifier add voltage (amplify) independent the amplifier current.
What is the Operating Principles of Moving Coil Instrument?
The basic principle of moving iron instruments is it works on the principal of magnetic repulsion....
it consists of two irons one stationary n other fixed to a moving pointer
small current flows through a coil surrounding the irons.this creates a magnetic field ,which magnetise the two irons..
the magnetise iron will develop a repulsion force between each other, this will cause the pointer to move against the spring
the pointer stop moving when the spring tension equals the repulsion force between the magnets...
Why neutral is not requied in 3 phase?
As far as I understand, you don't need neutral line for connecting appliances that is 3-phase compilant. You only need the neutral line to connect a single phase appliance, which you connect along with one of the three lines.
What is a common use for a stepper motor?
Applications of Stepper Motor:
Computer-controlled stepper motors are one of the most versatile forms of positioning systems. They are typically digitally controlled as part of an open loop system, and are simpler and more rugged than closed loop servo systems. Industrial applications are in high speed pick and place equipment and multi-axis machine CNC machines often directly driving lead screws or ballscrews. In the field of lasers and optics they are frequently used in precision positioning equipment such as linear actuators, linear stages, rotation stages, goniometers, and mirror mounts. Other uses are in packaging machinery, and positioning of valve pilot stages for fluid control systems. Commercially, stepper motors are used in floppy disk drives, flatbed scanners, computer printers, plotters, slot machines, and many more devices. Some people looking for generators for homemade Wind Turbines found success in using stepper motors for generating power.
What is the different high voltage equipment in the substation?
In a substation there are many items.
Circuit Breakers
Disconnectors
Earth Switches
Current Transformers
Voltage Transformers
Surge Arrestors
Power Transformers
Insulators
What will increase the voltage in a circuit?
There is a way to use capacitors to increase the voltage in an ac circuit. It increases it by about 50 %. It was used to increase the voltage going to motors. It is seldom used now that it is much easier to run a higher voltage line into a place of business. It does not work for Direct Current.
What is the advantage of polyphase system over single-phase system?
1) less copper cross section to conduct current
2) constant power to load
3) constant rotating magnetic field
4) Ideal for Direction Reversing
5) Current is not zero at any constant..
The primary definition of "rotor" is the metal circular disc... usually about 2/3 of an inch and varying in circumferance and removal mechanisms that attaches to the front axle spindle or the front axle out hub by your "studs" (lugs tighted the rotor onto the studs spindle, hub generally). The brakes pads are compressed by the "caliper" the caliper is governed by the brake pedel. YOU press very hard on the brake pedal... the caliper will compress TWO brake pads - on either side of the ROTOR grabbing it with friction and forcing the front axle to stop rotating as pressure is continually asserted upon the "rotor" by the "pads" through the "caliper" by the brake "pedal" applied by you. It is important to keep rotors - clean- straight (non-warped from too much tightening) turned- at each brake chage - have the rotors, as I said "turned" meaning "ground down to a slippery metal surface to optimize the pad application surface upon the rotor and a good contact between the two at EACH application of your foot upon the brake pedel. Lastly.... when buying... pads are a quick fix - rotors are not- sometimes you have to repack bearings and literally fight to get the rotor off... so buy a better grade rotor ... there are at least four (quality) tiers avalable... I see bembro listed quite often in these posts- they are special because they are drilled or slotted to create a cooler environment down there. After heavy stop and go traffic on interstates at night- watch the center area of the front wheels- and you may see a sports car's rotor glowing RED from heat. Anyway... hope this helps. 2dynamic
a brake rotor is the metal surface the brake pad is compressed against to slow down the vehicle. it spins with the wheels.
Answer Depends on what system you are talking about. A brake rotor is part of a disc brake system, and is the large, round, metal thing that your brake pads "squeeze" when applied. The pad contact with the rotor converts engergy of motion to heat energy, and that's what slows your car down. If the ignition system, the rotor is the rotating electrical contact in the distributor that channels voltage from the ignition coil to the individual cylinders.
In electrical engineering terms: in electric motors, dynamos/generators and alternators there are two different pieces used to create the electromagnetic field the units needs to work. the movable one is called the rotor and the fixed part is called the stator.
Where can you get electrical and electronics engineering projects?
Engineers are always in search of projects, and finding meaningful projects makes that search worthwhile within the Takeoff Edu Group. Listed below are some projects for electrical engineering ideas for such engineers.
What temperature is a soldering iron?
A soldering iron is a metal hand held probe type object heated by gas or electric for melting solder (a mixture of tin and lead). Solder is normally used for joining electrical wires and making soldered, leak proof, connections between pieces of copper pipe. It is however very hot, reaching temperatures of over 400 degrees Celsius.
It is a tool (usually copper) that is heated and then applied to a joint to melt the solder and heat the metal so it will accept the solder. Some are heated by electricity some are heated in a small furnace.
See "What is soldering iron" vipprogrammer.com/soldering-stations-manufacturers-36_116
it heats up your solder and makes it melt, it makes the joints in your circuit firm. it makes a little blob of solder.
What is the difference between neutral and earth wire in the distribution system?
Both conductors are at ground potential. They are connected together with a bonding jumper at the panel. The primary difference is the neutral is used as the return current path for single-phase loads, and the ground is the return path for fault current only. So, unless the hot conductor accidentally comes in contact with, say, a grounded equipment cabinet, there would be no current flow on the ground wire. The neutral wire carries current any time the single-phase load is in operation. With a three-phase balanced load, no neutral is necessary or required, yet electrical codes still require a ground wire for safety.
