0
What else can I help you with?
What is the need of extra high voltage transmission lines?
it is cheaper to use high voltage of transmission because, it is cheaper to boost the voltage up really high and keeps the current low, also the big pylons with huge insulators will reduce the energy wasted. the transformer have to step the voltage up for efficient transmissions and it bring back down to safe usable levels. the voltage is increase by a step up transformer it's then reduced again at the consumer end using a step down transformer. The only thing missing from the above narrative is the reason itself: Every conductor has some resistance. When an electric current flows through a conductor, the resistance of the conductor causes loss of some of the energy. The loss is LESS when the voltage is higher and the current is smaller. The big pylons, the huge insulators, and all the step-up and step-down transformers wouldn't be necessary if the voltage was the same 110 volts all the way from the generating plant to your house. But shipping it at high voltage saves more energy than the cost of all that extra infrastructure.
Causes of over temperature of induction motor?
the main reason is the amount of current flowing in the motor's winding is huge (over current) that why temperature begins to build up, continues using may end up to a burned motor. over voltage, defective bearing / bushing, shaft misalignment, defective insulation are some of the reason why motor experience over current.
Why is the voltage stepped up prior to the transmition across the national grid?
Electrical generators work at about 11,000 volts which is not enough to transmit power over long distances over about 5 miles. Therefore step-up Transformers are used to connect them to the local grid on 132 kV or the supergrid on 275 or 400 kV (in the UK)
What is the role of a transformer in the national grid?
A transformer changes electricity from one voltage to another - and in doing so, the current was alter in proportion (losses ignored) There is more than one reason why we need these. For example, to start with, the voltage which comes from most of the three phase alternators at power stations is often as "little" as 15,500 volts - but at very high current. This requires VERY thick windings, capable of handling many thousands of amps - even for quite a small power station alternator. Typically, this voltage will go through a "step-up" transformer which gives out around 400,000V which is then tied to the supergrid. This huge increase in voltage means that the cable can now be MUCH thinner. In addition to the reduction in copper/aluminium conductor sizes required, losses are also reduced as they are a function of I squared R (Current * Current * Resistance). So if you halve the current (by doubling the voltage), you reduce the losses to a quarter. A ten fold increase in voltage = 100 fold decrease in transmission losses (in a perfect world). Now, 400,000 is an efficient way to cart electricity around but is way to high for even heavy industry to use directly - so near cities you start to find substations which take in the power from the grid at 400,000 and transform it down to more manageable levels - first perhaps to 275,000 volts and 132,000v for some small pylons off to towns. Further substations then also take down to much lower levels for local industry and power transmission out to villages - 33KV and 11KV Finally when the power gets close to your home, it is transformed yet again right down to 415V which will also provide the regular 0-240 (230 soon) we all know and love. Keeping the voltage as high as possible until the end keeps losses to a minimum. The reason we do not operate everything at a high voltage is partly for safety and partly because high voltages can arc-over if the conductors are not kept very far apart. Something which is not practical or safe in the home. Some industry (eg: aluminium smelting) takes HUGE amounts of power and they DO take power from the grid at very high levels - even though they still end up using HUGE transformers themselves as the actually process uses quite low voltages - but at around a hundred thousands amps. (As and aside, they also have to rectify this, as the smelting process requires DC - not AC). DC does not work with a transformer, so all power is delivered to consumers as AC (Alternating current). *Final note* There are also some HVDC systems which use extremely high voltage DC to transmit power - and inverter systems to enable them to convert to AC and link to the grid. Advantages of HVDC links are that they can enable 50Hz and 60Hz systems to be linked - which using regular transformers is impossible. Using AC > DC ======= DC > AC however permits voltage AND frequency to be different at both ends of the system.
What voltage would you expect to measure across closed switch?
Original Correct Answer:The voltage across an open switch should equal the supply voltage.More Detailed Answer:The above answer is basically correct. However, it may not be EXACTLY the supply voltage.This is counter-intuitive at first glance and confuses a lot of people, including electrical engineers. The reason is this. Voltage, Current and Resistance are all interrelated by Ohms Law. Voltage equals Current multiplied by Resistance.It is easy to think that since a switch is open, then you do not have current flow through the circuit. Thus, current times any Resistance is equal to zero volts because the current is equal to zero. Thus, by this logic, you would expect to find zero volts across the switch. In actuality this is true.But, when you insert you meter, you change the conditions of the circuit, and the following is the result.Let's say that you have a circuit with a resistance load like a heater, and a inductive load like a motor. The switch that powers these devices is open, thus their is no current flowing through the resistance or inductive loads.Now you put the meter across the open switch. When you do, you insert a very large resistance in parallel to the open switch. Why? Because to get volts, the meter measures current flow through a known resistance, and then calculates voltage. To keep the resistance from impacting the circuit performance, the resistance is very large. Therefore, when you insert the meter, you will get a flow of current through the meter.Because of this large resistance, the current trough the resistance load, inductive load, and wires is very small. Thus, the voltage drop across the loads and wiring is very small. Therefore, it appears that the entire voltage in the circuit is across the huge resistance in the meter. The result is a voltage reading that is very near the source voltage.Let's do the math. Let's assume you have 120 volts. You also have a resistance of 500 ohms, and a motor winding that has 0 ohms resistance when DC is applied (This is true for motors). The meter has a 10 million ohm resistance.If these loads are in series, the total resistance is 10Million 500 ohms. The 11.9 microamps. By multiplying the current flow to each resistance, you get 6 millivolts across the resistance, no voltage across the motor winding, and 119.994 across the open switch or meter. Since a meter rounds it reading, you would get 120.If the loads are in parellel, you would get the same thing, becuase the switch is in series with both loads. In this example, the motor winding would have all the current flow through it since it is zero ohms, and the parallel resitance load is 500 ohms. Thus, the total resistance is the 10 million of the meter, and this resistance drive the current, and thus the largest voltage drop is at the swtich/meter. You could decide to remove the motor from this parellel circuit. If you did then the then the result is the series circuit above.
What is the need of extra high voltage transmission lines?
it is cheaper to use high voltage of transmission because, it is cheaper to boost the voltage up really high and keeps the current low, also the big pylons with huge insulators will reduce the energy wasted. the transformer have to step the voltage up for efficient transmissions and it bring back down to safe usable levels. the voltage is increase by a step up transformer it's then reduced again at the consumer end using a step down transformer. The only thing missing from the above narrative is the reason itself: Every conductor has some resistance. When an electric current flows through a conductor, the resistance of the conductor causes loss of some of the energy. The loss is LESS when the voltage is higher and the current is smaller. The big pylons, the huge insulators, and all the step-up and step-down transformers wouldn't be necessary if the voltage was the same 110 volts all the way from the generating plant to your house. But shipping it at high voltage saves more energy than the cost of all that extra infrastructure.
Is led bulb resistive?
LEDs are semiconductors, diodes in particular. The current flowing in an LED is an exponential function of voltage across the LED. The important part about that for you is that a small change in voltage can produce a huge change in current. That is the most important concept of this article. Resistors aren't like that. The current and voltage in a resistor are linearly related. That means that a change in voltage will produce a proportional change in current. Current versus voltage is a straight line for a resistor, but not at all for an LED.Because of this, you can't say that LEDs have "resistance." Resistance is defined as the constant ratio of voltage to current in a resistive circuit element. Even worse, there's no real way to know exactly the relationship between current and voltage for any given LED across all possible voltages other than direct measurement. The exact relationship varies among different colors, different sizes, and even different batches from the same manufacturer.
What is a carry on champ?
The person who carry huge luggage into the aircraft cabin.
How did ancient Egypt carry the huge bricks?
How did the egyptshions carry the big bricks?
How you would use the water flow to demonstrate a high voltage of electric current?
Electricity and water are often compared to help explain how electricity works. Voltage is like the speed of water in a river, and electrical current is like the amount of water in the river. Resistance can be compared to the physical width of the river. Power is voltage times current, or the speed of the water times the amount of water. Electricity is usually most dangerous when it is available at high power - similar to a huge, fast moving river.
Why do the transmission cables need to be thicker when power is transmitted at a lower voltage over long distances?
High-voltage transmission relies on the fact that for a given amount of power (watts), as the voltage goes up, the current (amps) goes down. The main issue with long distance transmission is voltage drop, which is proportional to current. Consider a transmission system supplying a 1 megawatt load. At 132,000 volts (3-phase), the current will be about 4.4 Amps (132kV X 4.379A X 1.73 = 1MW). Now, even 14 gauge wire would carry 4 or 5 amps, But the wire will have to be much larger than that to limit voltage drop to an acceptable level. The cost of the line itself is relatively small, BUT you have to buy transformers, one for each end! Utility-grade high voltage transformers are enormously expensive, and the hardware for high voltage transmission is also more expensive. Now consider a hypothetical transmission system supplying the same 1MW load, but now our transmission voltage is 4,160 volts. The current would now be 139 Amps! (4,160V X 138.9A X 1.73 = 1MW). You can see that the conductors must be very large to carry that much current. The problem is we still have to make the conductors larger to make up for voltage drop, and we end up with huge conductors. Of course, now you don't have to buy expensive high-voltage transformers! This is an extreme example just to make the point, by the way. At some distance, the cost of the transformers and associated hardware will equal the cost to eliminate them and just use larger conductors. At any distance less than that, it will be cheaper to use the low-voltage, high current setup. At any greater distance, the cost of the transformers, etc. will be more than offset by the cheaper transmission infrastructure (smaller conductors, etc.).
Why transformer not allow DC supply?
Transformers require changing magnetic flux to operate. DC current provides a steady current, with no changes in magnetic flux that can be picked up by the output coil. Alternating current has continuously changing direction which produces continuous changes in the magnetic flux. This induces changing voltage in the output coil. This is (or was) the huge advantage of AC power systems worldwide: The voltage could be easily changed from high voltage for generation and transmission into low voltage at the consumer. DC generators had to run at the voltage required by the consumer and powerlines could not be higher voltage / lower current than the consumer. Today, switching systems easily convert DC to other DC voltages, DC to AC, etc. This is done in most computers, telephones, stereos, etc. It can even be done on a grand scale, allowing use of high voltage DC power lines in selected places.
Is led bulb resistive load?
No, LED bulbs are considered as a non-resistive load. They are semiconductor devices that convert electricity into light using a diode. LEDs operate by controlling the flow of current through the diode, rather than resisting it like traditional incandescent bulbs.
How do you know which direction current flows in?
We always visualize, and assume, current to be flowing from the positive terminal of the power supply or battery to the negative terminal, through the conducting path provided by everything that's connected between them. In reality, though, the thing that's doing the actual physical flowing is huge numbers of electrons, which happen to carry negative charge. So the actual physical flow is in the opposite direction.
What is a Kiloampere?
It is a HUGE amount of current 1000 amps
Why ac transmission voltage is 765 kv?
For a given load, the higher the supply voltage, the lower the resulting load current. So high voltages are essential for electricity transmission, in order to avoid enormous voltage drops, a need for conductors for huge cross-sectional areas, and to reduce line losses. Actual transmission sytem voltages are determined by the electricity-supply standards used in the country in which you live.
Why don't we try to capture the huge amounts of electrical energy available in lightning?
I wondered about this myself. It may be a technical challenge, I am not sure. You don't actually need to capture the lightning itself; the lightning is the result of a huge voltage difference between the upper atmosphere, and earth. A current might be generated from that.The things that would have to to be researched are:1) How significant is the energy density really?2) Is it possible to overcome the technical problems related with the huge voltages (millions of volts)?3) Would there be any ecological problems if mankind saps large amounts of voltage, thus reducing the stored energy?I wondered about this myself. It may be a technical challenge, I am not sure. You don't actually need to capture the lightning itself; the lightning is the result of a huge voltage difference between the upper atmosphere, and earth. A current might be generated from that.The things that would have to to be researched are:1) How significant is the energy density really?2) Is it possible to overcome the technical problems related with the huge voltages (millions of volts)?3) Would there be any ecological problems if mankind saps large amounts of voltage, thus reducing the stored energy?I wondered about this myself. It may be a technical challenge, I am not sure. You don't actually need to capture the lightning itself; the lightning is the result of a huge voltage difference between the upper atmosphere, and earth. A current might be generated from that.The things that would have to to be researched are:1) How significant is the energy density really?2) Is it possible to overcome the technical problems related with the huge voltages (millions of volts)?3) Would there be any ecological problems if mankind saps large amounts of voltage, thus reducing the stored energy?I wondered about this myself. It may be a technical challenge, I am not sure. You don't actually need to capture the lightning itself; the lightning is the result of a huge voltage difference between the upper atmosphere, and earth. A current might be generated from that.The things that would have to to be researched are:1) How significant is the energy density really?2) Is it possible to overcome the technical problems related with the huge voltages (millions of volts)?3) Would there be any ecological problems if mankind saps large amounts of voltage, thus reducing the stored energy?
