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What is the maximum insulation resistance for a 230 volt 50hz domestic circuit if there is one Explain your answer?
Wiki User
∙ 11y ago
This maximum insulation resistance is in the order of Mega-ohms there's a good chance the insulation resistance tester (Megger) will max out it's display to look similar to this: >99MΩ
or whatever your display can show. The one we used frequently in work did. It was calibrated regularly to Irish electrical standards.
*Warning* If you leave lamps in place or don't disconnect electrical equipment from the wall socket you risk pumping high voltage into your device and destroying it. You must also disconnect your main earth from the board you are testing or you will back-feed to the mains incomer transformer where the Earth is neutralised and it will show a false short circuit. It goes without saying do not remove the earth if the board is live. In this case remove the earth belonging to the circuit you are testing.
So, the meter tests the insulation resistance, and it does this by V/I=
R or Ohm's law.
Important: Voltage here is not 230v
The meter should have selectable voltages dependent on what you need to meter. But it is generally 250/500/1000 volts. For this problem we'll use 500 volts to test our cables.
I (the current flowing between insulation sheaths of 2 cables, which is hopefully incredibly low, otherwise you have a short circuit) hence
500/some really small number =
R =
Insulation Resistance
500/.0001 =
5,000,000 Ω
5 million ohms won't register on any meter properly so you end up with the maxed out scale as discussed.
Check your local Regulations for details on what is considered a pass/fail in your location. In Ireland the current Regulations say the test is fail when producing a result lower than 0.5M
Ω or 500,000
Ω
In theory the answer to your question is this:
Infinity is the maximum insulation resistance for any circuit, however that is based on absolutely no flow of current between the two cables, which will never happen, so You'll have to do with M
Ω.
The only time you should be worried about insulation resistance test values is where
the meter starts to properly register them. The smaller the final resistance, the worse the insulation is on your cable and the more likely you have a problem. Approaching 0
Ω
resistance it becomes clear there is a short circuit.
Wiki User
∙ 11y ago
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What is the cause of unsymmetrical three phase short circuit?
By definition a short circuit is the path of least resistance of current flowing through a circuit be it three phase or single phase. The main cause of this condition in electrical circuits is an insulation break down. This break down can be caused by overheating of the insulation to a point where the insulation disintegrates from the conductor that it is supposed to be protect. With the insulation missing from the wire there is the possibility of a short circuit to surrounding grounded material. The other cause of insulation break down is from vibration. Unsupported conductors can vibrate against their metallic enclosures to a point where the insulation is just worn away. Once the insulation becomes thin enough the voltage will bridge the insulation threshold and take the path of least resistance to ground and a short circuit will occur.
What does it mean to say that a conductor is grounded?
the hot wire in the circuit has come in contact with a ground ------------------------------------------------------------------------------- not true, if a circuit is grounded properly the outside ( as in the outside of a drier ) is connected to the ground to prevent shocks . it gives electricity a route to go that is away from you. <<>> The first answer is correct, because the circuit is grounded. The second answer refers to equipment grounding for safety reasons. <<>> The first answer is a short circuit which will blow a fuse or trip a circuit breaker. If a circuit is grounded in AC it's for saftey like the second answer, in DC it's the route the electricity takes back to the battery from the circuit.
The number of ohms in a circuit is a measure of the?
The electrical resistance of the circuit
How does the loading effect of an ammeter in a low resistance circuit compare to the loading effect in a high resistance circuit?
The voltmeter has an internal resistance, which should be as high as possible. As this resistance draws current from the circuit under test, it will affect circuit operation. This is more pronounced in a high impedance circuit because the current drawn flows through higher resistances.
Open circuit and short circuit test?
Open circuit means the circuit is not continuous . A short circuit is continuous but has a fault connecting between either live to neutral or earth .As result of this we saw that this answer is unsufficent to explain short and open circuit on the other hand you can use this answer also like i did:)
Why you do insulation resistance test?
in order to avoid unwanted short circuit break downs.... short circuit can burn the transformer and motor winding.... Megger is the device used to check the insulation .
What test would identify a short circuit in a lighting circuit?
earth continuity insulation resistance polarity
What is the cause of unsymmetrical three phase short circuit?
By definition a short circuit is the path of least resistance of current flowing through a circuit be it three phase or single phase. The main cause of this condition in electrical circuits is an insulation break down. This break down can be caused by overheating of the insulation to a point where the insulation disintegrates from the conductor that it is supposed to be protect. With the insulation missing from the wire there is the possibility of a short circuit to surrounding grounded material. The other cause of insulation break down is from vibration. Unsupported conductors can vibrate against their metallic enclosures to a point where the insulation is just worn away. Once the insulation becomes thin enough the voltage will bridge the insulation threshold and take the path of least resistance to ground and a short circuit will occur.
What would happen to circuit if there was no resistance?
a circuit with no resistance or zero resistance can be considered as open circuit in which the current is zero. without resistance the circuit just becomes open ()
What is the purpose of earth connection in a domestic ring circuit?
To provide a low-resistance return in the event of a earth-fault current occurring anywhere in the circuit. The requirement for a low-resistance return is to ensure the resulting fault current causes the relevant protective device to disconnect the faulty circuit.
Explain the utility of fuse with propes example?
when high voltage creats in circuit board then fuse difused him self and save the circuit board. for ex>>>>wire resistance....
What is difference between Hipot and IR test?
With Hipod leakage current of any circuit (HT Distribution/ Transmission Lines) can be determine and with IR Test insulation resistance between two circuit or parts of machine is determined.
What are the types of power transformer test?
open circuit & short circuit test, insulation resistance test, turns ratio, efficiency, if it is oil cooled then breakdown voltage of oil, voltage regulation and definitely visual inpection...
Is the increase in voltage causes a greater electric resistance in a circuit?
No, the resistance in a circuit does not change when voltage changes. Resistance is an inherent property of the circuit.
Explain how changing the resistance in a circuit chages the current?
Ohms' law says if voltage stays constant resistance controls the current flow. Resistance goes up, current goes down. E/I*R.
How is the total resistance in a series circuit is determined?
The total resistance in a series circuit is determined by adding (summing) the individual resistances of each component in the circuit.
Why you Removal of lamps from lighting outlet points When carrying out an insulation resistance test on this installation?
I'm not sure exactly what you're asking, but it sounds like you are wanting to test for any potential weak spots in insulation which would allow for stray current to pass through. You would want to set the circuit so that it would be an open circuit, so that if it was truly an open circuit, no current would be flowing through the circuit, where if some breakdown in the insulation allowed for a current flow, then you would be able to detect it.
