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What is the formula to check insulation resistance of 3 phase ac motor with insulation tester?
Wiki User
∙ 13y ago
you would want to use a meg-ohmeter (to measure high values of resistance)
you would test from each phase wire to the motor housing frame (to check for unwanted ground faults)
if the windings are isolated, you would also check between each set of windings (if the winding are internally connected as part of the manufacturing process, you will read low resistance between the windings because they are in essence spliced to each other and therefore this test would be meaningless)
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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.
Wiki User
∙ 12y ago
Wiki User
∙ 13y agoMinimum insulation resistance of motor
20*en
insulation resistance = ---------------
1000+2p
en - rated voltage of motor
p - rated power of motor in kw.
Wiki User
∙ 13y agoThere is no such thing a polarity in AC voltage or current. It changes back and forth 60 cycles a second.
Wiki User
∙ 12y agoCheck all 3 wires for shorts to ground (motor case).
check all 3 wires for continuity to each other.
Check for proper voltage at the leads
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How do you measure insulation resistance between windings for 120KVA alternator?
Use a megger or a insulation tester. Place one lead on any of the phases nd other lead the alternator boy. Observe the indicator. In megger it s good with infinity or it must be minimum 100M OHM, IF IT SHOWs 50 it could be coz of moisture in winding by heating the alternator the insulation resistance value may improve
How do you identify a burnt out motor without meggering?
If the motor is still connected to its electrical supply and it is safe to do so switch it on and check for an odour of burning insulation and or the presence of smoke. A burnt out winding can cause a motor to run very slowly and make a unusual humming noise, if this cannot be achieved safely then make sure the motor main switch is isolated and sniff around any ventilated area of the motor to check for the smell of burning insulation. If you have a circuit tester that will check for continuity then use this after firstly completely isolating the motor from its electrical supply and disconnecting the wiring to the input terminals. You may see and open circuit reading between the live and neutral terminals or a short circuit between one or the other terminal when the tester is connected between the terminals and the metal case of the motor, remember that a circuit tester will read resistance so try the test on the appropriate setting, example; RX10K
When are megger testers used?
On the whole megger testing is a non destructive test. 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.
How do you Secure insulation to interior of rectangular metal duct work?
I really dont know but I will tell you to check out some articles at www.High Beam.com and you can check out HGTV on TV and they always put in insulation!
What are the approximations of open circuit and short circuit tests?
Firstly turn of the power before this test...Using a resistance or continuity tester you should get the following results:Short circuit: Very low resistance (nearly 0 ohms) or the bell will ring.Open circuit: Very high resistance (Somewhere in the range of Mega ohms) or the bell will not ring.The reason for this is because and open circuit has a gap in it (which has high resistance).The short circuit has wires that are crossed and so has a really low resistance.
How do you measure insulation resistance between windings for 120KVA alternator?
Use a megger or a insulation tester. Place one lead on any of the phases nd other lead the alternator boy. Observe the indicator. In megger it s good with infinity or it must be minimum 100M OHM, IF IT SHOWs 50 it could be coz of moisture in winding by heating the alternator the insulation resistance value may improve
How can you know that power cable need to be replaced?
you check the insulation and it is degraded,hole in it or it does not have a very high ohms of resistance,which means the insulation is bad.
Can insulation resistance of cable be checked with a volt meter?
No. A volt-ohmmeter will not check insulation. To check cable insulation you need a special device (called a megger) made for the purpose that imposes a high voltage and measures current leaks.
How accurate are the readings of a megger test?
While using megger we only have to see whether resistance breaksdown at the upper value mentioned. Since megger generates high voltage we can check whether breakdown takes place or not.Megger has a range from o to infinity.So it is not possible to find accurate resistance,hence it is used as an insulation tester
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 .
Why 5KV voltage is applied to Megger for insulation resistance measurement?
It is a easy voltage to obtain and can check for breakover in the insulation. The voltage is higher then what would be put through most wire and shows any weakness.
What is the function of a insulation tester?
An insulation tester is s meter used by electricians and cabling technicians to check the quality of the electrical installation. The insulating materials coating the copper conductors can be nicked, chafed or nibbled by rats either during installation or during it's lifetime. The tester generates a high DC voltage of around 500V to 1000 V. This high voltage is applied in series with a sensitive ammeter to one conductor to electrical earth or between two open circuit conductors. Any current flowing through the meter wiil be effectively via the insulation or perhaps through a water ingress fault. Any value of leakage current above a recommended threshold has to be investigated,repaired and tested again. The unit is also used to check the quality of the copper terminations and resistance of the conductors. Again,any high resistance reading will need to be checked to ensure tight terminations otherwise a fire may ensue during periods of heavy current load on the cable.
Is r-value good or bad?
it is a good thing i think R Value is the thermal resistance of a given material. The higher the R Value the more thermal resistance and the better the insulation. So, an R48 roof system is warmer than an R32 roof system. All insulation materials are rated by their R Value. An inch of rigid insulation has a higher R Value than an inch of fiberglass insulation. Check with the insulation manufacturer for the R Value.
What is meggers?
A megger is an electrical instrument that is used to measure the resistance of insulation by applying a DC voltage to the conductor. One lead is connected to the conductor and the other lead is connected to ground. Safe insulation reading to ground should be above 2,000,000 ohms or 2 megs.
How to check for an ungrounded wire?
You can use a wire tester to check for a ungrounded wire. Attached the wire tester to the battery posts. The tester will show you if the ground is weak or strong.
What is a land tester?
land tester is use for check a utp cable..if is worth
What does a portable appliance tester do?
A portable appliance tester is a device used to check the safety and electrical integrity of electrical appliances. It typically performs tests such as insulation resistance, earth continuity, and polarity checks. This helps ensure that appliances are safe to use and comply with electrical safety regulations.
