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Electrical Wiring
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4,935 Questions
Would 8 kva generator run a small house?
Yes, an 8kVA generator can run a small house. A generator this size should be able to adequately power a one ton air conditioner, 18 cubic foot refrigerator, and other small appliances normally found in a small house.
What are the calculation for overload relay for three phase motor?
If a motor 3 phase or single phase goes above the full load amps that is on the nameplate of the motor then it is in overload condition. This is usually caused by trying to drive machinery with less horsepower that the manufacturer recommends To protect the motor from this condition overload heaters are put in series with the supply voltage and the motor leads. If the current from the motor draws more that the motor's nameplate FLA then the overload heater opens the supply voltage through use of a motor contactor. The contactor can not be closed again until the motor overload heaters cool down and by the same token the motor gets a chance to cool down. This condition is rectified by either using a bigger HP rated motor or lowering the load on the machinery that the motor is driving.
What is the difference between a single phase compressor and a 3 phase compressor?
One uses single phase AC current (120/240), the other uses 3 phase AC current (most households will not have 3 phase in their home) One uses a 3 phase motor the other a single phase motor. 3 phase is usually used in industrial applications while single phase is used in home or small business apps.
Why three phase meter is better than single phase meter?
A three-phase meter can be used for single phase while the reverse is not the case.
What does ohm's law depend on?
The law applies to all temperatures, even when the material properties change with temperature; the temperature characteristics of the material are assigned to the resistance, so that the law still holds.
AnswerThe original answer isn't quite correct.
As temperature affects resistivity, the resistance of a conductor may change if its temperature is allowed to increase. For pure metal conductors, the resistance generally increases as the temperature increases.
Ohm's Law ('the current flowing along a conductor, at constant temperature, is directly proportional to the potential difference across that conductor') only applies when the resistance of the conductor is constant so, when verifying Ohm's Law, the temperature must be kept constant, in order to keep the resistance constant.
It should be pointed out that the ratio of voltage (U) to current (R) is called resistance (R), and the resistance of a circuit can be found from the equation, R = U/I whether Ohm's Law applies or not -but Ohm's Law itself only applies when the ratio is constant over a range of voltage variation.
Read more: What_is_the_significance_of_the_constant_temperature_reference_in_ohms_law
What size breaker is needed for feeding 10 kva transformer at 460 v single phase?
One horsepower (electric motor) is 746 watts, so ten horsepower is 7460 watts. Divide that by a power factor (assumed) of 0.8 and you get 9325 volt-amps. Divide that by a voltage (again, assumed) of 240 and you get 39 amperes.
For calculation purposes the electrical code book states that a 10 horsepower motor at 240 volts will draw 50 amps. The motor's nameplate amperage that is driving the rotary phase converter should all ways be used first.
The electrical code requires a breaker for a motor to be 250% of the motor's operating full load current. 250% of 39 amperes is 97 amperes. I would use a 100 ampere breaker for a 10 horsepower motor.
If the motor rating is used from the code book values, then 50 x 250% would equal 125 amps and that is the size of the breaker that must be used. This is the reason that the motor's exact name plate amperage rating should be used. In the long run feeder wire costs could make a saving in the overall projected costs.
An appliance that takes 120V, like a toaster, is connected to one half of the split 240 volt single phase and to the neutral. The neutral should always run at zero voltage and is required to return the current which comes back from the load to the power station.
A large appliance, like an electric stove or a clother dryer, is usually of the type that needs a lot more power, so - to keep the current draw as low as possible - it requires more voltage. This is supplied by connecting it to the full 240 volts single phase service by using both "split phases": the 120V "hot" with red insulation and the 120V "hot" with black insulation, along with the neutral. The neutral is used to provide power at 120 volts to a time clock and/or an appliance programmer (e.g. for the drying cycle time on a dryer) which don't usually run on 240 volts.
Some 240 volt appliances, like water heaters and some air conditioners, take the full 240 volts from both red and black hots but don't need a neutral.
Equipment having much larger motors, like elevator motors or motors driving machine tools in factories, usually use a 3 phase service, either with no neutral - called a "delta" configuration - or with a neutral, which is called a "star", "Y" or "wye" configuration.
For more information see the Related link and the answers to the Related questions shown below.
How a generator changes rotary motion into electricity?
Mechanical energy is the energy of work. Back in the olden days, brave inventors used steam to power turbines, or used water to turn wheels in a river. These are examples of putting mechanical energy to work. The gears inside a wind up clock need mechanical energy to function.
How insulation test is prform on megger?
A megger test is used to look at the insulation properties of motor windings, electric wiring, high power antenna mounts, and other similar items. The voltages are a lot higher than they are with a normal Volt-ohm meter. You will turn the device off and connect it to a source of power. The circuit breaker being testing should be closed and then disconnect the line-side circuit. Connect the output terminals and turn on the test set. Get the desired current and make any necessary adjustments. Then, you will hit the 'start' button and get your readings.
Why is an ordinary transistor known as a bipolar transistor?
because once saturated it will conduct current both way
raja TOQEER (Pakistan)
Megger test
On the whole megger testing is non destructive. What happens is a DC voltage is applied to the device or winding under test. It is an insulation test to see is the insulation has been injured in any way to cause a short circuit when normal power is applied to it. On my megger there are 3 ranges 300V, 750V, and 1000 volts. Applying the proper voltage is essential to not damaging the device you are testing. Working voltages up to 240 volts should use the 300 range. Working voltages up to 600 volts use the 750 volt range and working voltages above 600 use the 1000 volt range. As you can see if you used the 1000 volt range on a device that had a working voltage of say 24 volts you could damage the insulation just by testing it. So meggering a device is non destructive if you use the tester as its instructions tell you to.
What are the advantages of 3 phase generators as compared to single phase generators?
For those who need a three-phase supply, they are essential. If a single-phase supply is needed, a three-phase generator is uneconomic.
Three-phase is used for loads of more than about 15-20 kVA.
A: Brown B: Orange C: Yellow Neutral: Grey Ground: Green or Green with a yellow stripe.
Since power is current times voltage, doubling current while keeping voltage the same will double the power. Ignoring slight non-linearity, if the power doubles, the heat will double.
Is there a difference between a mains adapter and a power adapter?
The English term mains electricity usually refers to the general purpose alternating current (AC) electrical power supply. The term is not often used in the USA and Canada. There, mains power has a variety of names: These include household power, household electricity, domestic power, wall power, line power, AC power, city power, and grid power. So you see, that a mains adapter must be a power adapter.
What are dangers of stealing electricity from the national electricity grid?
The same as stealing anything else.
With the exception that you're deeling with high voltages and power. To steal electricity, you'd need to modify or create a connection to the electric grid. Depending on the magnitude of power you pull, this can be detectible by the power company immediately, or will be detected given enough time. But the main point is you have to get close to the line, which is a bad idea to say the least, unless you are trained, and have the proper protective equipment.
Besides this, you face prosecution when (not if) caught.
What is the function of the junction box on a three-phase motor?
Junction Box - an octagonal shaped electrical material where the connections or joints of wires are being done. It is also where the flush type lamp holder is attached. This could be made of metal or plastic (PVC) Polyvinylchloride.
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The function of a junction box is to suppress the spread of fire. In an electrical system the most likely spot for a fire to start is where wires are connected together. Loose connection of joined wires will create a resistance point. Over time with the current flowing through the connection it will heat and cool. This increases the resistance. Without repairs to this situation there will come a time when this heat will reach a combustible temperature. The junction box will suppress the spread of this fire by cutting off the oxygen supply to the fire. If the wire connection junction was in an open wall adjacent to combustible products, the fire could spread to wall studs and then combustion could overtake the whole house.
How do you convert 5kW to amps if your voltage is 120?
P, the power in kW (kilowatts) is related to V (the supply voltage) and I (the current in amps) by the Power Law:
P = V x I
So, to get the current:
I = P / V
If you have something that uses 5 kW (which is the same as 5000 watts) and the source voltage is 120 V,
then the current drawn in amps = 5000 / 120 = 41.67 amps.
This is probably a high-power industrial kiln intended for use in a factory where a 3-phase power supply would regularly be installed. The cost of getting such an industrial kiln converted to run on a normal house mains 240 Volt power supply (even if conversion were possible, which is not certain) would probably not make sense as it would be cheaper - and safer - to buy a secondhand kiln that was designed to run on 220 - 240 Volts.
A specialist supplier of such equipment might be willing to take the 3-phase industrial kiln in part exchange. <><><>
As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized.
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
What lasts longer a series circuit or a parallel curcuit?
They will both last for the same amount of time. In both situations all of the battery's power is being used, but in parallel, you can separately control the individual loads that you put on the circuit with switches.
Hope that helps
Permanent magnet field motors. With a these motors, a permanent magnet is used to replace the field coil. DC power is connected via the brushes, to the armature only. Reversing the polarity, will cause the motor to reverse its direction of rotation. It is very common to use a switch to intentionally reverse to the polarity, to allow reversal of the motor if desired.
How many watts of electricity are used for a stadium?
The input voltage can vary, in 230V countries the gear tray (which converts the supply into a controlled voltage and current suitable for the bulb) may have an 230-240V or 380-415V input.
The voltage at the lamp itself depends on the size of the lamp, smaller ones may run at about 90 volts, larger ones at 220-270 volts. However, in order to start (strike) the lamp a high voltage pulse is applied, this may be up to 30,000 volts.
What are high voltage electric wires made of?
Primary utility wiring uses an ACSR cable, (Aluminium Conductor Steel Reinforced). The multiple strands of aluminum wires are wound around a center steel cable. The steel center is used to allow longer spans between poles or towers. Ordinary aluminum wire can not be long spanned because its weight would break the wire. All other high voltage wiring is done with different insulation thicknesses dependant upon what the voltage is. The higher the voltage the thicker the insulation. Insulation of the wires stops when the conductors carry kilo voltages usually above 5000 volts.
