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Electrical Wiring
Ask questions here about proper wiring and electrical installation here.
4,935 Questions
How can you have a ground fault protection in a 3 phase 3W system?
3 phase ground fault detection on a 3 phase system requires that the vector summation of all three phase currents be measured. The vector sum of these currents should equal zero, or nearly zero for a balanced system. If a ground fault exists, then the vector sum will not equal zero. This condition must be validated using i2t techniques in order to eliminate false trips.
What is the correct way to wire an electric motor capacitor since the capacitor is not marked?
Motors that use capacitors are single-phase AC motors.
The capacitor is used to "start-and-run" the motor. The capacitor is wired between the incoming hot service wire and the "start-and-run" terminal of the motor. The other terminal of the motor is connected to the outgoing neutral service wire.
These capacitors are designed to run on AC (two DC capacitors back-to-back) so It doesn't make a difference which way round the two terminals are wired.
If the case is metal it is usually grounded to the ground wire.
Some motor "start and run" capacitors are plastic-cased so don't need any ground wire.
Is it worth fixing an iron that keeps blowing fuses in your house?
It may not be the iron that is the problem. It might be what else is on that same circuit that you plug the iron into. To check the problem out, unscrew the fuse and see what else on the circuit shuts off. If there are any loads that can be unplugged do so. Then try the iron again and see if the fuse blows. Try the iron in another plug from a different circuit, if a different fuse blows then its time to get a new iron.
When telegraph wires are hung sufficient sag is left Why is this so?
The amount of sag is relative to the tension in the suspended cable.
The tension in a cable is naturally distributed evenly along the entire length of the cable, by virtue of the sag. I'm not positive, but I think that the naturarlly occurring shape of the curve is described as a "catenary" curve.
The less the "droop," indicates a greater tension, and the sag versus tension ratio IS NOT LINEAR, meaning that to get ever more sag pulled out of a cable, takes tremendouly increasing higher tension.
The amount of tension required to pull a heavy cable perfectly straight, or horizontal. is ASTRONOMICALLY HIGH, which almost always exceeds the tensile strength of the cable itself.
This means that if one were to try to pull all the sag out of a suspended cable, at some point, the cable would break. So, as a result, a certain amount of sag is left in a suspended cable.
When I was in the Army, the Signal Corps Pole Linemen, had charts which they eventually learned by heart, which indicated, for any given line size/weight per foot, the proper amount of sag to leave in the cable in order to not exceed the safe tension.
Reverse running of three phase meter?
The reverse running of a three phase meter is possible when one of the meter's two potential coils fails. This is a problem found typically on a Delta service. A three phase meter in this condition is damaged and will report lower energy use than actual.
Define median signal strength?
Median signal strength is a number such that the actual signal is higher than that number 50% of the time
and lower than that number 50% of the time.
Plug and socket, plug and socket outlet, plug and receptacle or plain plug and outlet all seem to be in common usage in the US. Plug and socket is possibly the only wording commonly used in the UK. [Plug and socket outlet sounds ok to a me, as a Brit, but we never really use that expression in the UK. Plug and outlet or plug and receptacle actually sound very strange!]
What size of contactors used for 20hp star-delta starter?
The size of the contactors are dependant upon what the voltage the motor is operating on.
c a utility construction electrician
Why does my automatic warehouse door go up but does not come back down?
Check for the mechanical. On the wiring site, it has different cables for up and for down, but same hardware (just switch the phase, then motor got different rotation). So if mechanical is okay, check the cables wiring
How motor can control using timer contactor?
Control means, a timer cant control is speed directly, it can control its operation. A times will have NO nd NC contacts. Connect the motor in series with the timer contacts wrt desired operation
What two things must happen to cause an silicon controlled rectifier to fire?
You must have a voltage on the gate that exceeds the turn-on threshold of the SCR. Typically around 0.65v. Then you must maintain a minimum holding current from Anode to Cathode. Once turned on, the SCR will remain self latched in the on state until the current through the Anode and Cathode falls below the minimum self holding current.
True.... absolutly true... i know because i did the 7.2a worksheet and got it wrong cuz i put false.
Haha, I am doing that right now. Thanks for the answer!
What colors are Hot or Live wires and what colors are Ground or Earth wires?
- the Hot or Live wire is a color other than white, green or gray. The most frequently used color for a hot wire is Black, followed by Red, Blue, Yellow, Orange, Brown. Some colors are conventionally used for specific types of hot wires. For example three-phase connections.
- the Neutral wire is colored White or Commercial Gray
- the Ground or Earth wire is colored Green or is bare wire. Sometimes the Ground is Green with a yellow stripe--this is most often used for isolated grounds.
- the Live or Hot wire wire is coloured Brown
- the Neutral wire is coloured Blue
- the Earth or Ground wire is coloured Green and Yellow
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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 is the minimum clearance of service wires above a sidewalk in feet?
The point of attachment of service wires shall not exceed 9 m (30 ft.) above grade or side walk.
The clearance of supply conductors at any point above finished grade will not bet less than, 5.5 m (18 ft.) across highways, streets, lanes, and alleys, 4m (13ft.) across driveways to residential garages, 5m (16 ft.) across driveways to commercial and industrial premises and 3.5 m (12 ft.) across ground normally accessible to pedestrians only.
How do you install a hitch on a 2002 Dodge Durango?
I just did this for my 2002 SXT. Go to etrailer.com, buy the custom "Hidden Hitch" brand receiver. It is a direct bolt in that you won't even have to drill a hole for. They also sell the plug in trailer wiring harness. I bought both and the 7 flat-pole round adapter. For install, remove spare tire, have someone help you lift the hitch into position. It will be obvious where the bolts go at that point. Put the flat threaded steel plates on top of the factory frame holes and tighten all 6 bolts. The wiring harness has great instructions, I threaded mine through the sub frame of the bumper. A little more work, but I know the wires will never droop down and get torn up. Then put the spare tire back in.
How do you convert Amps to KVA for a single phase system?
use 1.0 as your PF Understand that K=1000, so KVA simply means thousands of volts times amps. First, multiply KVA by 1000 to get VA, then divide by the voltage of the system to get amps. Example: 6KVA, 240V single-phase. 6 * 1000 = 6000 VA 6000 / 240 = 25A
What happens to the current Amps flowing in a circuit when you raise or lower the frequency Hertz?
<> <> <> This question is not asking about household power circuits which typically have an almost constant frequency of 50 Hz or 60 Hz. If a circuit includes inductance and capacitance then the answer below, marked by *** is incorrect. That answer is correct for purely resistive loads only.
An electric motor has inductance as well as resistance. The circuit inside a typical fluorescent light fixture contains a ballast - which has resistance and inductance - and a tube, which has capacitance, inductance and resistance. The currents flowing in the motor and the fluorescent light fixture would vary considerably if the frequency of the applied alternating voltage was allowed to alter.
Two other common examples:
i) a Hi-Fi or similar audio amplifier, driving a loudspeaker: the speaker has a coil in it which has inductance. The current (and hence the output power) of the speaker varies considerably with the audio frequency, typically between 20 Hz and 20,000 Hz (20 kiloHertz). For that reason different sized speakers - such as tweeters, mid-range, woofers and sub-woofers - each having different sizes of inductance and capacitance, are commonly used to produce the best "total overall sound output" from an amplifier.
ii) a tuning circuit for a radio: this must use both an inductance coil and a tuning capacitor. The current flowing in those components varies enormously between "out-of-tune" and "in-tune" settings of the tuning capacitor which makes the circuit tune "in" and "out" of radio frequencies in a specific range which the tuning circuit was designed to handle. Radio frequencies range between 50 kiloHertz and hundreds of GigaHertz or more. <> <> <> Changing the power source from AC to DC may have an effect on the current drawn but is dependent on the nature of the load. Any device is designed for AC or DC operation but rarely both. <> <> <> *** Note: the following answer is incorrect except for purely resistive loads. ***
The frequency of an AC voltage line has no effect on the current drawn for any given power. Voltage does have an effect on the current. <><><>
What is the difference between the voltages in the coils A and B in three phase generator?
I assume that you are referring to phase A and phase B? So what happened to phase C, in that case?
The answer is that the magnitudes are the same, but phase B (and phase C) are displaced by 120o. The normal phase sequence (the order in which each voltage would reach its peak value) would be A-B-C.
