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When using a megger at 1000v and your reading is 2700 megohms is it a problem?
Wiki User
∙ 15y ago
What is the acepable rating on a #3 wire when meggering @1000v
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∙ 15y ago
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What does 4007 represents in 1n4007 transistor?
A 1n4007 is a diode and not a transistor, the 4007 don't really represent anything, the 1n4007 is a axial lead standard recovery rectifier, working peak reverse voltage = 1000V, the forward current for this device = 1 Amp. More data about it can be find in the data sheet.
Why are power lines more dangerous than the electricity wires in your home?
Higher voltage and effectively unlimited current.house wiring is 120V to 240Vneighborhood distribution power lines are 1000V to 5000Vcity and industrial distribution power lines are 20,000V to 50,000Vintercity high tension transmission power lines are 100,000V to 1,000,000V
Why to use centre tapped transformer in bridge wave rectifier?
In a rectifier, a center-tapped transformer and two diodes can form a full-wave rectifier that allows both half-cycles of the AC waveform to contribute to the direct current, making it smoother than a half-wave rectifier. This form of circuit saves on rectifier diodes compared to a diode bridge, but has poorer utilization of the transformer windings.
What is the highest reading you can achieve with a 1000V Megger?
It reads 100, 250 1,000 DC for both 200MΩ and 2000MΩ ranges.
When to use 1000 volts megger?
to measure insulation resistance in devices that operate below 1 volt for practical insulation like 300v building wire you need a 1600V megger 2 * operating voltage + 1000V a vom that uses 9V or a 1000V megger wont tell why a GFCI is tripping it wont see pinholes or air gaps it wont see carbon tracking or flashover
What is the output voltage of an insulation tester which is required to test a 230v circuit?
On a hand crank megger which is used to test insulation breakdown, use the 300V setting. If the megger does not have that setting use 500V as opposed to 1000V for the test. The output of the megger is a DC voltage.
What is the standard reading in megger testing to conclude that the equipment is passed and or failed?
Meggers send voltage thru the cables to determine the resistance between, meggers like the mj145 have multiple settings from 100 volts to 1000v, a Megger showing a good reading will show megaohms thru its full band, a bad one reading will be indicated by it either reading 0 ohms or less then 30 ohms (depends on the circuit and what's between the wires) a bad indicator can also be a steady reading at low voltage then at higher voltage it spikes to a low ohm, or a low voltage, like as if u just created a short. What that shows is at low voltage your insulator is fine, but at high voltage it blows thru it, normally that means your Insolator around your wire is damaged.
What should be the minimum insulation value of a 20 kw 415v phase motor?
415V commonly available wire is 300V or 600V so that would need to be 600V wire to use a megger or a hipot tester (2* operating voltage +1000V) 2000 volt megger or hipot should verify the wiring in this instance 2500v megger will be necessary for 600V wire and wiring devices you also must look and ambient temperature and humidity a test after some operation time can verify this
Is there a standard and safe range for insulation resistance of motors or it's dependent on type of motorsif 30 Mohm is safe for a motor with 1000 Mohm of insulation resistance in normal conditions?
"INSULATION resistance is not about standard nd safe range because resistance value depend upon the application for which we are providing it in what range the current flows." The answer above is incorrect. Application and current rating & range have nothing to do with insulation resistance. There are standards available for insulation resistance testing both in terms of the test procedure and the values. IEEE Standard 43 provides a basis for insulation resistance testing. Both NETA ATS (Acceptance Testing Specification) and NFPA 70B gives criteria for insulation resistance testing. Insulation Resistance (IR) testing, also known by the slang terms meggering or megging, is a procedure where the quality of the electrical insulation is evaluated to determine if it is acceptable for service. It is also used to compare against previous measured values to determine if there has been any degradation to the equipment being tested. In this case we are talking about motor insulation. The question deals with two comparative readings and wants to know if the value of 30 megohms is acceptable. First we should clarify the test methods and results. NETA ATS 2007. Section 7.15.1 covers AC induction motors and generators. The testing involved is broken down into those motors 200 hp (150 kw) and less, and those > 200 hp (150 kw). The test voltage value is based upon the voltage rating of the motor's winding and is found in table 100.1: Rating = 250V; Test Voltage = 500 VDC; Minimum Resistance = 25 megohms Rating = 600V; Test Voltage = 1000 VDC; Minimum Resistance = 100 megohms Rating = 1000V; Test Voltage = 1000 VDC; Minimum Resistance = 100 megohms Rating = 2500V; Test Voltage = 1000 VDC; Minimum Resistance = 500 megohms Rating = 5000V; Test Voltage = 2500 VDC; Minimum Resistance = 1000 megohms Rating = 8000V; Test Voltage = 2500 VDC; Minimum Resistance = 2000 megohms Rating = 15000V; Test Voltage = 2500 VDC; Minimum Resistance = 5000 megohms Rating = 25000V; Test Voltage = 5000 VDC; Minimum Resistance = 20,000 megohms Rating = 34500V; Test Voltage = 15000 VDC; Minimum Resistance = 100,000 megohms It is important to note that the values given are based on a standard temperature of 40C (or sometimes 20C depending on the engineer's specification). You must correct your readings to a standard temperature as the value on the insulation's resistance is going to vary inversely with temperature. That is as temperature increases the resistance will decrease. The rule of thumb is that the measured value will halve for every 15C above standard and will double for every 15C below standard. As an example let us say that we have a 25 hp induction motor rated 480 VAC. The ambient temperature is 15C. Using our table we would set the tester to 1000 VDC and take a reading for one minute. At the end of the minute we get a reading of 450 megohms. Per NETA ATS Table 100.14 the correction factor is 0.31 so IR = 450 megohms x .031 = 139.5 megohms. The minimum acceptable value is 100 so this motor is acceptable. On the flip side if the motor is in a very warm process area, say 50C, then temperature correction factor is 1.59 thus IR = 450 megohms x 1.59 = 716 megohms. As you can see the temperature makes a very large difference in the results! This discussion up to this point has been about a spot-reading check. However for a true check we want to know the Dielectric Absorption value. There are two different standard tests for Dielectric Absorption. The first is the Dielectric Absorption Ratio (DAR) and the second is the Polarization Index. DAR = Reading @ 60 sec / Reading @ 30 sec. Let us say that the 30 sec reading = 325 megohms and the 60 sec = 450 megohms. Thus: DAR = 450 megohms / 325 megohms = 1.38 The minimum DAR per NETA is 1.4 so this particular motor is borderline at best and should be investigated further. PI = Reading @ 10 min / Reading @ 1 min. Let us say that the 1 min reading = 450 megohms and the 10 min = 1100 megohms. Thus: PI = 1100 megohms / 450 megohms = 2.44 The minimum PI per NETA is 2.0 so in this case the motors is acceptable. One final factor that should be taken into consideration is Relative Humidity (RH). The amount of moisture present in the air also affects the measured test values. The more moisture then the lower the reading. There is no published standard correction factor for RH however when NETA Techs perform these tests then they always record the RH for baseline comparison. The bottom line is that the readings will vary based upon temperature and humidity. A reading on warm humid day may be acceptable whereas the same reading on a cold dry day may not. So the question asked here is unanswerable as there is not enough information given. What were the temperatures at the time of the readings? Was it dry during one and raining during the other? What does the person asking mean by "normal conditions"? I highly recommend that anyone interested in this subject get the free book "A Stitch in Time" by Biddle at: http://www.biddlemegger.com/biddle/Stitch-new.pdf Please note that I also changed the category from Health/pregnancy to Electrical Engineering.
What is the volume of pyramids?
it depends on the size
Why insulation resistance test is required?
every insulator has its own voltage range depending on its intended use. we test insulation for the required operating voltage range. usa uses a document known as nfpa 7 or nec most common residential wiring 120v to ground is in the 300V class the specified test voltage for 300V wire and wiring devices is 2 times the working voltage +1000v which is 120v x 2 + 1000v = 1240V spec 1600V for industrial wiring its 600V class wire and wiring devices 480V x 2 +1000v = 1960V spec 2200V for most uses a 2500 volt megger is sufficient
Do you have Megger testing procedures and measurement limits for power cables at 600V rating 250mm plus 50mm THHN?
For 600V insulation Megger NETA & IEEE recommends: Test voltage = 1000V Test Duration = 1 minute Test Value = 100 Megohm minimum (corrected to 20 degrees C) Typically you megger conductor to conductor and conductor to ground. Most will not megger for the full minute and it is up to your discretion. Just watch that the resistance continually increases during the test period. If it is decreasing then you should hold the full minute and investigate the reason. For multiple conductor cables then twist all of the conductors together and pull out one at a time and megger it to the bundle. This will expedite thetesting into as few as tests possible while still thoroughly checking the cable. Note that test voltage and values are based strictly on the insulation rating and the conductor size is pretty much irrelevent.
What is high voltage motors and low voltage motors?
None: "high tension" is just another way of saying "high voltage".
How do you set up a megger to test insulation resistance on self regulating heat tracing?
One lead will go on the braided shield (this is essentially the ground), the other lead goes on the heating conductors. Megger either one lead at a time, or both conductors under the same lead. I usually test at 1000v - follow manufacture's spec if unsure. You cannot test line to line with a megger. Testing line to line with an ohmmeter is of some use, as the ohmic value will be dependent on the length, wattage and, to some degree, the temperature of the heat trace. This test is most useful with more than one run of identical heat trace, or to track one piece over time. Values far outside of what is expected will indicate damaged (open or shorted) heat trace.
Can you use 300v cable for 240v?
You most certianly can. Voltage ratings on wires are 300V,600V and 1000V. These are the maximum voltages. 120 - 240 on 300V, 480 - 575 on 600V, 1000V wire is a special order used for specialized equipment.
