Electrical Wiring

It resist the flow of current according to the resistance value.

In India maximum generation is 21.5kv

Care must be taken to ensure that the relay does not operate from the spill current resulting from unequal CT saturation during motor starting, where the high currents involved will almost certainly saturate the motor CT's. It is common to use a stabilising resistor in series with the relay. The effect of the stabilising resistor is to increase the effective setting of the relay under these conditions, and hence delay tripping. When a stabilising resistor is used, the tripping characteristic should normally be instantaneous. An alternative technique, avoiding the use of a stabilising resistor is to use a definite time delay characteristic. The time delay used will normally have to be found by trial and error, as it must be long enough to prevent maloperation during a motor start, but short enough to provide effective protection in case of a fault.

Inductors in Series - L total = L1 + L2 +L3. Inductors in Parallel - 1/Lt = 1/L1 + 1/L2 + 1/L3 Resistors in Parallel - 1/R total = 1/R1 + 1/R2 + 1/R3 Resistors in Series - R total = R1 + R2 + R3

Most electrical wires use unalloyed copper. The exception is high-power overhead lines that use aluminium for its low density, which means there is a lot less mass for the towers to support, so they are lighter and less expensive.

Aluminium overhead cables are either ACSR - aluminium core, steel reinforced, which uses multi-strand cables with steel strands in the centre; or AAAC which is all-aluminimum alloy conductor.

AAAC cables use an aluminium-magnesium-silicon alloy with silicon 0.5-0.9%, magnesium 0.6-0.9%, iron 0.5% max, copper 0.1%, manganese 0.03%, chromium 0.03%, zinc 0.1%, boron 0.06%. The purpose of adding other elements is to increase the tensile strength of the conductors so they can be tensioned up without too much dangling.

The incoming voltage from the source goes to L1,L2 and L3 terminals. The Load connects to T1, T2, and T3. The coil voltage goes to A1 and A2. The stop ,start circuit is in series with the N.C. contacts on the contactors overload block. Usually numbered 95 and 96.

z=rl +XL in a series circuit. if XL increases and r remains the same, z will increase. z is a complex number and the magnitude is z=(r^2 + (XL)^2)^.5. if the vector part of z increases z increases.

Yes, IF the motor is a dual-voltage motor to begin with. There should be re-connection instructions on the motor nameplate, or available from the manufacturer. The motor will list both voltages on the nameplate. If it only lists one, then the motor cannot be re-wired to a different voltage.

Two voltage sources in series can either add up or cancel out depending on which way round they are orientated. If the two positive or the two negative terminals are connected together, the overall voltage is the subtraction of the two. If the positive terminal from one supply is connected to the negative terminal from another, the overall voltage is the sum of the two.

This could be a sign of stress or something more serious. If this persists, it would be wise to see your doctor.

No. The amperage isn't high enough for you to be harmed by it.

No, across the tongue it can't kill you. If someone opened up your chest and put the battery across your heart then you might be in trouble...

Possible. If you have a heart condition, pace maker, etc. then there could be problems any electrical voltage no matter how minor. Also, if the battery touches a nerve close to the surface of your tongue, it can cause other issues.

On top of that, not all batteries are made to specs, just ask Sony. With manufactures farming out to other vendors, they loose track of quality control. A battery that is not to spec will provide the jolt to seriously injure someone.

A ring main circuit for example is:

key:

circuit breaker=0

cable=----

socket=[]

bends in cable=/ and \

Using the key this is a demonatration.

0---[]-----[]-------[]------[]---[]---\

\---[]-----[]-----[]----[]-------[]---/

Just imagine that there is only 1 circuit breaker in that circuit, both ends of the ring main should link up to that 1 breaker.

A radial circuit consists of just 1 cable going to the circuit breaker with sockets on the cable but there is no return path on a radial.

A ring main is just like a big circle with 2 ends of cable and sockets around the circle=both ends of the cable linking to the circuit breaker.

Inductor impedance is given by jwL, where w=2*pi*frequency. Therefore as the frequency increases the impedance of the inductor increases, causing a larger current flow and a larger power dissipation across the inductor

They shouldn't, usually it is the other way around. As with all wire, the temperature effects wire lengths. When wires become warm as in a hot summer day the wires expand and droop and likewise when they become cold as in winter they contract and tighten up. The wires have to be installed to take this condition into consideration. There is a specific engineered sag allowed for each type of conductor from pole fix point to pole fix point.

Stranded conductors are made up of many smaller solid conductors. In order to bunch the solid conductors to make the stranded wire they have to be held together. The simplest way of doing this is to twist them together. Once the solid wires are twisted together they are drawn through a machine that applies the insulation coating which holds the solid wires together. The final result is a insulated stranded conductor that has good flexibility. With this flexibility multiple stranded conductors can be easily be drawn through conduit systems that incorporate up to four 90 degree bends between junction boxes.

The question you pose doesn't make a lot of sense. An RPM is a unit of rotation and an amp is unit of electrical current. You can't convert these units just willy-nilly. Now if you were wondering about the correlation of RPMs in an electrical dynamo and the current produced, that would make more sense... I'm just not sure what you're asking.

It does not matter to the motor, just as long as the three phase voltage is what the motor specification requires.

HOWEVER..... While the motor will run in either star or delta, it will draw 3 times as much current in delta as it does in star, and will develop 3 times more torque (and power) in delta compared to star.

3 phase motors are often started in star, as it draws less current and is less likely to blow fuses, damage contacts and upset the supply system due to voltage drops. When the motor is near full speed, the motor is switched to delta connection for full power. This is called star-delta starting, and is suitable for light, low inertia loads such as fans or pumps. Because of the motor's reduced startup torque, it shouldn't be used for compressors, machines with heavy flywheels, or machines that come onto load before they reach full speed. Motors designed for star-delta starting will have 6 live terminals in their connection box.

Let's get a little bit technical. In star, each winding has L-N voltage across it (about 58% of the L-L voltage applied when in delta) - in Australia, our voltage from the active (live wire) to the neutral (return wire) is 230 volts, and the voltage from one active to another active is 400 volts. (230 / 400 is about 0.58, or 58%. and 400 / 230 is 1.73 or 173%). Connecting a motor in star puts 230 volts across each winding, and connects ONE winding to each supply phase. when running, it draws (say) 10 amps, and develops about 6 kW / 8HP. In delta, each winding has 400 volts across it, and each supply line powers 2 windings, so the current increases by 1.73 (400 volts compared to 230 volts) and again by 1.73 (2 windings on a 3 phase system draw 1.73 times more current than one winding.) 1.73 squared is 3 - so in delta, the motor draws 3 times more current (30 amps), and delivers 3 times more power (18kW / 24HP).

Some motors are designed to be operated ONLY in star - they may have a label advising you of this, or they may have only one value of voltage and current on the nameplate. They will also usually have only 3 terminals inside the connection box. If you suspect that the motor is 'star only', but want to make sure, connect the motor in delta, and check the running current as soon as the motor is up to speed; if it is drawing more than the nameplate current, or the motor is noisy in delta, but not in star, stop the motor immediately and reconnect it in star, or the motor WILL burn out very quickly.

They will not be very different.