Electrical Engineering

A centrifugal switch, once the motor reaches near run speed, centrifugal force causes a set of contacts to open and disconnect the start capacitors. Some larger motors use a contactor which is disconnected by the centrifugal switch.

Ohm's law gives the relationship between current, voltage, and resistance. The law states that I=V/R, where I is current, V is voltage, and R is resistance.

Source: university digital fundamentals

Like many engineering classes require, computer engineering should be taking with prerequisites of electrical engineering. Computers in this field are used for the curriculum. The difference between computer engineering and computer science is that computer engineering deals with the hardware of a computer, or all the things you can see when you open a computer up, like the motherboard or hardrive. comp science deals with the software such as programs like Microsoft word for example

Wind energy is made by spinning turbines. The wind spins the wind turbines and they generate energy.

An electromotive force is the potential difference developed by a voltage source, and is necessary to cause current to flow through a circuit. Strictly-speaking, it is the open-circuit potential difference of a battery, generator, etc. An alternative definition is that an e.m.f. is equal to the sum of the voltage drops around any closed loop, including any internal voltage drop.

well the working of the step doen transformer depends on the number of turns on the secondary side of the transformer, now in the case of a step down transformer, the number of turns in the secondary windings are less as compared to the number of turns at the primary side/winding, so the amount of flux which links the secondary side of the transformer is also less resulting in the production of less amount of emf at the secondary side.

hence the status of the voltage is decreased as compared to the voltage of the primary side.

The internal resistance of a cell is not constant because a cell needs to move and be flexible in order to undergo various osmosis or diffusion processes.

Check the nameplate on the actual breaker. Some breakers are rated for AC or DC. If it doesn't specifically list DC on the nameplate, then no, you should not rely on the breaker to adequately protect the circuit.

damper winding help to maintain the magnitude phase shift (on load chages) between rotor an stator flux and kill some parasite currents produced by the leakage flux moving out the rotor winding to the rotor core.

Electrical and Electronics engineering

Series resonant circuits have their lowest impedance at the resonant frequency. Parallel resonant circuits have their highest impedance at the resonant frequency. This characteristic is exploited in the design of filters, oscillators and other circuits.

if it is a three phase motor it can be run an the single phase mains but it woild require a hand start in either direction, if you put a capacitor on line two and three and the live and neutral on line one and two then it should work

synchronous input means that the flipflop reads input only at posedge or negedge of the clock.

In a parallel circuit the failure of one bulb reduces the light of that one bulb. In a series circuit the failure of any bulb causes all bulbs to stop producing light because the circuit itself fails. A break in a series circuit stops the current flow to the whole circuit. A break in a parallel circuit stops the flow only in that parallel branch, not the whole circuit. This independence from system loss by one failure is a parallel advantage.

A portable propane generator is a great choice for nearly everyone looking to buy a generator. Not only does propane provide a great fuel for the generator, it is much easier to store tanks of propane than it is to store gasoline. Although choosing what fuel you want in a generator is a great first step, there are still several things to consider when purchasing a propane generator. Thing to look at before purchase include price, wattage, size, and brand.

The price of a portable propane generator varies greatly depending upon what it is going to be used for. They typically range in wattage from around around 1200 watts all the way up around 8,000 to 10,000 watts. If you plan on mainly using it while fishing or at a campground, the lower wattage should be great. If you plan on being able to do things like power a refrigerator, though, you should go with one that is closer to 10,000 watts. If you choose to go with the 1200 watt generator, you can expect to pay around $100-$150, which really is not bad. However, if you are going to purchase a generator in the 8,000 to 10,000 watt range, you should expect to drop around $900 or more.

Another important thing to consider when purchasing a generator is the size. You will want to figure out exactly where you are going to store it before you go to the store to purchase it. A generator is not something that you will want sitting somewhere in the corner of your house, so clear a large enough space for it and at least 2-3 tanks of propane in case of emergency.

Finally, the brand of the generator is also important. While name recognition is not everything, it does mean a lot in this particular case. There are a many brands of generators, but you should try to stick to brands such as Champion.

By keeping these recommendations in mind, you can feel confident in your selection. Portable propane generators are right for most people. When you fire yours up, you will realize that you made the right decision.

An analog meter will respond to linearly as current is present . digital meters cannot do that not until the conversion is complete. in essence an analog meter is human friendly as compared to a digital meter. both have their places in applications.

Parallel Operation of DC Generators: In a dc power plant, power is

usually supplied from several generators of small ratings connected in

parallel instead of from one large generator. This is due to the following

reasons:

(i) Continuity of service: If a single large generator is used in the power

plant, then in case of its breakdown, the whole plant will be shut down.

However, if power is supplied from a number of small units operating in

parallel, then in case of failure of one unit, the continuity of supply can be

maintained by other healthy units.

(ii) Efficiency: Generators run most efficiently when loaded to their rated

capacity. Therefore, when load demand on power plant decreases, one or

more generators can be shut down and the remaining units can be

efficiently loaded.

(iii) Maintenance and repair: Generators generally require routinemaintenance

and repair. Therefore, if generators are operated in parallel,

the routine or emergency operations can be performed by isolating the

affected generator while load is being supplied by other units. This leads

to both safety and economy.

(iv) Increasing plant capacity: In the modern world of increasing

population, the use of electricity is continuously increasing. When added

capacity is required, the new unit can be simply paralleled with the old

units.

(v) Non-availability of single large unit: In many situations, a single unit

of desired large capacity may not be available. In that case a number of

smaller units can be operated in parallel to meet the load requirement.

Generally a single large unit is more expensive.

Connecting Shunt Generators in Parallel: The generators in a power

plant are connected in parallel through bus-bars. The bus-bars are heavy

thick copper bars and they act as +ve and -ve terminals. The positive

terminals of the generators are .connected to the +ve side of bus-bars and

negative terminals to the negative side of bus-bars. Fig. (1) shows shunt

generator 1 connected to the bus-bars and supplying load. When the load

on the power plant increases beyond the capacity of this generator, the

second shunt generator 2 is connected in parallel with the first to meet the

increased load demand. The procedure for paralleling generator 2 with

generator 1 is as under:

(i) The prime mover of generator 2 is brought up to the rated speed. Now

switch S4 in the field circuit of the generator 2 is closed.

(ii) Next circuit breaker CB-2 is closed and the excitation of generator 2

is adjusted till it generates voltage equal to the bus-bars voltage. This is

indicated by voltmeter V2.

(iii) Now the generator 2 is ready to be paralleled with generator 1. The

main switch S3 is closed, thus putting generator 2 in parallel with

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generator 1. Note that generator 2 is not supplying any load because its

generated emf is equal to bus-bars voltage. The generator is said to be

"floating" (i.e. not supplying any load) on the bus-bars.

Figure(1)

(iv) If generator 2 is to deliver any current, then its generated voltage E

should be greater than the bus-bars voltage V. In that case, current

supplied by it is I = (E - V)/Ra where Ra is the resistance of the armature

circuit. By increasing the field current (and hence induced emf E), the

generator 2 can be made to supply proper amount of load.

(v) The load may be shifted from one shunt generator to another merely

by adjusting the field excitation. Thus if generator 1 is to be shut down,

the whole load can be shifted onto generator 2 provided it has the

capacity to supply that load. In that case, reduce the current supplied by

generator 1 to zero (This will be indicated by ammeter A1) open C.B.-1

and then open the main switch S1.

Load Sharing: The load sharing between shunt generators in parallel can

be easily regulated because of their drooping characteristics. The load

may be shifted from one generator to another merely by adjusting the

field excitation. Let us discuss the load sharing of two generators which

have unequal no-load voltages. Let E1, E2 = no-load voltages of the two

generators R1, R2 = their armature resistances

V = common terminal voltage (Bus-bars voltage). Then

1

1

1 R

I E V 

 and

2

2

2 R

I E V 



Thus current output of the generators depends upon the values of E1 and

E2. These values may be changed by field rheostats. The common

terminal voltage (or bus-bars voltage) will depend upon (i) the emfs of

individual generators and (ii) the total load current supplied. It is

generally desired to keep the busbars voltage constant. This can be

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achieved by adjusting the field excitations of the generators operating in

parallel.

Compound Generators in Parallel: Under-compounded generators also

operate satisfactorily in parallel but over compounded generators will not

operate satisfactorily unless their series fields are paralleled. This is

achieved by connecting two negative brushes together as shown in Fig.

(2) (i). The conductor used to connect these brushes is generally called

equalizer bar. Suppose that an attempt is made to operate the two

generators in parallel without an equalizer bar. If, for any reason, the

current supplied by generator 1 increases slightly, the current in its series

field will increase and raise the generated voltage. This will cause

generator 1 to take more load. Since total load supplied to the system is

constant, the current in generator 2 must decrease and as a result its series

field is weakened. Since this effect is cumulative, the generator 1 will

take the entire load and drive generator 2 as a motor. After machine 2

changes from a generator to a motor, the current in the shunt field will

remain in the same direction, but the current in the armature and series

field will reverse. Thus the magnetizing action, of the series field opposes

that of the shunt field. As the current taken by the machine 2 increases,

the demagnetizing action of series field becomes greater and the resultant

field becomes weaker. The resultant field will finally become zero and at

that time machine 2 will be short circuited machine 1, opening the

breaker of either or both machines.

Figure (2)

When the equalizer bar is used, a stabilizing action exists and neither

machine tends to take all the load. To consider this, suppose that current

delivered by generator 1 increases. The increased current will not only

pass through the series field of generator 1 but also through the equalizer

bar and series field of generator 2. Therefore, the voltage of both the

machines increases and the generator 2 will take a part of the load.

1800 Humphry Davy develops the first electric light, the arc light.

1860 Sir Joseph Wilson Swan develops the carbon paper filament. In 1878 he demonstrates his lights in Newcastle, England.

1877 Charles Frances Brush manufactures lights that were used to illuminate streets and some businesses in Cleveland, Ohio.

1879 Thomas Alva Edison improves the modern incandescent lamp.

The true advantage of digital wattmeters over electromechnical wattmeters is the cost to operate the meter. Also, virtually all digital meters can emitt a radio signal to forward the power useage for a certain time period to a recording device. This means that a utility can drive around the block rather than manually walking up to each house and recording the power usage every month. The best electromechanical wattmeter has a power consumption of 24Watts. The leading Centron digital meter has a starting power of less than 5Watts. The operating power consumption for electromechanical meters is also more than that of digial meters. Loss of electromechanical meters is ~ .7Watts Loss of digital meters ~.5Watts The display could be considered an advantage also because people who are not trained in reading a scaled meter can read a digital meter easily, however, if they aren't trained in reading a meter they most likely will not understand what they are reading anyway.

Yes.

Certain types of motor. The best for this are DC motors with a permanent magnet field.

DC motors with a field windings, need an excitation voltage to produce power.

Simply rotate the motor, with an external force and DC current comes out of where you normally put power in.

AC motors, induction motors, (squirrel cage type, typically used for domestic fans) are no good.

In the context of electrical cables, PVC and XLPE are two materials used as insulation. XLPE has got more capacity to hold on incase of high temperature. XLPE will not deteriorate it's insulating property until it reaches 90 degree celsius. It will not suddenly lose it's insulating property if the themperature jumps just above 90. But the overall life of the cable will be reduced. PVC can withstand temperatures only upto 70 degree Celsius.

PVC is cheaper than XPLE, hence it's find it's place in market today.

PVC is a thermo plastic where as XLPE is thermosetting plastic.

PVC - Poly Vinyl chloride

XLPE - Cross linked Poly Ethylene

The definition of MCB is a miniature circuit breaker, it trips if there is a line to natural fault. Ill add some extra information about the different types.

RCD - residual current device = This is what you could separate you're circuits up with by inserting 1 of these in you're consumer unit (if you have lets say 10 circuits it goes like this...

rcd-mcb-mcb-mcb-mcb-mcb-rcd-mcb-mcb-mcb-mcb-mcb-main switch.

you see the rcd's control 5 circuits each, if 1 of these circuits had an earth fault on it, the rcd will trip and 5 of them circuits will go off, which means you have to keep tripping in you're rcd with an mcb 1 at a time to see which circuit the fault is on.

RCBO - residual current breaker with overload protection- These can be installed in place of mcb's and rcd's, the rcbo is an mcb and rcd in 1 breaker. For example, i have installed a consumer unit full of these, in this case if a circuit forms a fault then its only that circuit that goes off.

I hope this extra piece of information helps you along and best of luck.

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In electrical terminology MCB stands for Miniature Circuit Breaker.