Electrical Engineering

when the current is passing through the winding then it is called "Excitation".

Types of excitation

(1)seperately excited generator.

(2)self excited generator.

self generator is classified into 3 types.

1.shunt generator.

2.series generator.

3.compound generator.

compoud generator is again classified into 2 types.

1.short shunt generator.

2.long shunt generator.

When an AC circuit contains both resistance and inductance the current and voltage will be in phase. This means having waveforms that are of the same frequency and that pass through corresponding value.

An R-L circuit is one having both resistance and inductance. These are naturally-occurring quantities that most circuits possess and, so, don't necessarily have any practical applications per se. However, a practical example of an R-L circuit is an electric motor whose windings have both resistance and inductance.

It is around 12.5 Amps, assuming the crosssection of one strand of cat 6 is of .5 sq mm and four strands are twidted together.

Because the supply voltage is common to each branch of a parallel circuit, each appliance receives its rated voltage which is necessary for the appliance to operate at its rated power. This is the main reason. Another reason is, should one appliance fail, then -unlike a series circuit- the other appliances will keep working.

The squirrel cage is skewed so that the force applied to the rotor it continuous. If they were straight then the force would be jerky, as whole of the bar is cutting the magnetic field lines at the same time. With the bars skewed the amount of the bar cutting the field line grows continuously and the next bar starts cutting the field lines as the first finishes.

also, slots are skewed to get uniform torque ,reduce the magnetic locking (also called COGGING EFFECT) between stator and rotor,and thirdly to reduce the magnetic humming noise during running condition

Firstly the suffix '-ance' in each of those three words indicate the properties the material exhibits.

Therefore resistance is the property by which any material tends to oppose the flow of current through it.

Inductance is the property by which a material opposes the change in current, or opposes an alternating current. An inductor can be appreciated simply using a coil of insulated wire, or a solenoid.

Capacitance is the property by which a material opposes the change in voltage across its ends, ie how it opposes alternating voltage. A capacitor comprises of, essentially, two metallic plates separated by a dielectric (a medium which may/may not be non-conducting, but is capable to contain charge).

cheers!!

A moving coil microphone is used for a variety of audio applications primarily for recording and sound reinforcement. It can be used in a wide range of situations from professional recording studios to live performances and is the most common type of microphone in use today. Its versatility and reliability make it a great choice for many different applications.

• Recording: Moving coil microphones are used to capture audio in the studio such as vocal and instrumental performances spoken audio and sound effects.
• Live sound reinforcement: Moving coil microphones can be used in live sound reinforcement situations such as concerts theater performances and public speaking events.
• Broadcast: Moving coil microphones are used in broadcasting applications such as radio and television.

Moving coil microphones offer a number of advantages including high sensitivity low self-noise and low distortion. They are also relatively inexpensive and easy to use making them a popular choice for many different audio applications.

Adding a resistance in parallel to another resistance will reduce the equivalent resistance.

Parallel Equation:

R1 = 10Ω

R2 = 20Ω

Req = R1R2/(R1+R2) = (1/R1+1/R2)-1

Req = 10•20/(10+20) = 6.67Ω

If you are dealing with AC voltage, you can use a transformer. You can find transformers at places like Radio Shack, Jaycar and some online sites like eBay. Transformers have to be connected in the right way. You have to connect the voltage you are going to increase to the low voltage side and on the high voltage side will be the voltage which has been stepped up by the transformer. (If you want a DC voltage out, you will need to connect a bridge rectifier to the output, followed by a large capacitor and then a voltage regulator of the voltage you want out.)

If you are dealing with DC voltage then you will need a chip to step the voltage up. These chips can step voltage up from around 1 to 10 volts to at least 20 to 30 volts. These chips also need to be connected correctly. You will need more components than using a transformer. You will probably need some capacitors and some resistors. Depending on the IC you choose, you will find many circuits on Google for it and how to build them.

By far the easiest type of voltage to step up is AC. If you have the option of AC, and need to have a very high voltage output, you are better off using a transformer, bridge rectifier and a rectifier.

With increasing torque load the armature tends to slow down; the motor draws more current to compensate, and if there is armature resistance the back emf generated by the armature falls to allow the increased current to flow, which causes the motor to settle at a lower speed.

The mechanical output power is the speed times the torque, and increasing the torque increases the power output provided the speed does not drop much.

The motor needs the current and magnetic flux to create

motion

The magnetic field is created by field winding where as

armature carries the current resulting into the rotation of

armature

because in laboratory almost we are using only three phase equipents,so we require more pewer in laboratory, thats why we are generating high voltage in laboratory.

Single phase motor will not start automatically unless it has a start and run winding.

This is also known as spread spectrum. It's a method of encoding a signal using a changing carrier frequency. FM radio is incoded using a single carrier frequency which is varied slightly to encode the information. Think of frequency hoping as FM, but with the carrier changing quickly. So instead of staying on 88.1, the signal starts on 88.1, then jumps to 95.2, then to 101.3, then to 81.5, etc. etc. Each transmitting and receiving device knows the pattern of carrier jumps, so it knows where to look for the information. This is how bluetooth works.

resistance is directly proportional to wire length and inversely proportional to wire cross-sectional area. In other words, If the wire length is doubled, the resistance is doubled too. If the wire diameter is doubled, the resistance will reduce to 1/4 of the original resistance.

Incorrectly connecting a multi-phase motor could potentially cause a huge problem. Inside of the cover where the motor leads reside (we call them 'pigtails') is a diagram of the lead connections. They are wired for typically either 230V or 460 Volt AC operation

There are a number of advantages why three phase (delta or Y configuration) is preferred over single phase circuit. The best advantage is that the each of the three lines in a three phase circuit can act as single phase thus effectively getting three single phase circuits in one transmission. Another advantage is whether it's single phase or three phase, the generation is the same, therefore three phase has more practical value. Also, the instantaneous power in single phase falls to zero but in three phase system, the net power from all the phases is continuous.

Injecting power into the higher voltage winding of a transformer will make it act as a step down transformer; injecting power into the lower voltage winding will make it act as a step up transformer. A transformer can be used both ways.

Hi first of all Vector group used to determine the PHASE shift of the TRANSFORMER as well as the PRIMARY and SECONDARY connection information.

Let taken an example:-

YNyn0d1 It means CAPITAL LETTERS indicates the primary side of winding detail's small letters for secondary side detail's DELTA CONNECTION Symbol D OR d is used and connection WYE used Y OR y for PRIMARY and SECONDARY.

If WYE connection is their neutral always come so we used suffix N OR n.

Now check PHASE angle Difference (PHASE ANGLE) see the last NUMERIC VALUE give correct information.

Suppose we connect/compare two TRANSFORMER we first see its VECTOR GROUP if they matched then we do move to any connection.

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to be protect the motor and electrical equipments.some circuit provide to protect the motor.for exm.DOL starter, OLR to protect the motors....