The best I've seen and heard so far notably on the How the low voltage setting differs from the high voltage setting for fault detection and its effect on the needle sweep This truly makes the Megger unique
Halfway through I was saying "Such a fault would show up with a common DMM!". Ha! Very good explanation of HV insulation testing and its value. Still valuable 5 years on (and for as long as we'll be using induction motors...)
The low voltage used by a standard multimeter in the "resistance" mode may not detect certain insulation breakdown faults like a megger will. The difference has to do with the non-linear behavior of insulation faults: they don't exactly follow Ohm's Law (current proportional to voltage) like a conductive connection does. Compromised winding insulation may register as "inifinite" ohms (open) when tested with low voltage, but will "break down" and conduct when subjected to a greater voltage.
"Ground resistance" in a power system usually refers to the low expected resistance between the grounding conductor and earth ground. This is different from insulation resistance which is expected to be very high.
A fuse or breaker will most often trip on a wye connected transformer, however on a delta-delta connected transformer it will not trip, instead you will have one leg (on a 3-phase) with no or very little voltage and the other two phases (lest say its a 3 phase 480v system) would read 480 volts to ground rather than phase to phase. just thought I would point that out to all the troubleshooters out there.
Good & useful device. My concern is knowing which setting to use. Use the 500V & up for high powered motors & 100V or lower for low powered motors, the right?
The test voltage should go up with the devices voltage. 1/4HP motors can be made 120 volts, 240 volts, 480 volts One tests the higher voltage units are a higher voltage. Thus a 2HP motor for 120 volts can be tested at a lower voltage than a 1/4HP motor for 480 volts electrical-engineering-portal.com/measurement-of-insulation-resistance-1
A faulted motor winding may act like this, but it's unlikely. The voltage output by an inverter even at low speeds will likely cause excessive current with a faulted motor winding. There isn't any harm in doing a megger check of the motor (be sure to disconnect it from the inverter first!), but the problem most likely lies elsewhere.
Is it also possible that you can demonstrate how to perform the "No-Load Test (AC or DC)" , Load Point Test (AC or DC) & Locked Rotor (AC) on motors. bdw, thanks for sharing the video.
Often, it will trip the overcurrent protection device (e.g. breaker or fuse) if the fault is phase-to-phase. A ground fault on its own may blow the fuse or trip the breaker, but only if the three-phase power system is hard-grounded (e.g. a Y-connected source with the center point firmly bonded to earth ground).
I have been using a 500v megger on 240 and 380 volt motors for years without problems (though i am not an expert on this) Just be careful there are no temperature sensors or thermistors in the winds as these will fail if tested to such a high voltage.
A good motor would be over 20M ohm, may even be in the Giga ohm range. A motor that has damp in the windings would probably run ok if it was over 1.5M ohm and then dry out as it warmed up. It depends on the supply voltage the motor is designed to run on a bit, this is for 240V 50hz motors.
That meter is a fantastic bit of kit, a generic copy of the Robin / kewtech from the 80s/ 90s. There now made by a number of manufacturers and use different brand names Fad demo and video
I just want to clarify something, which somehow has to do with IR testing. If a windings resistance testing fails, the insulation resistance test must not be carried out. Is this true ?
Im confused;At the high voltage setting the tester shows a short 0 ohm to ground and the short is detected.On the lower voltage or green setting the tester shows 0 ohm too.Does that not mean that even on the green setting lower voltage the short is still picked up by showing 0 ohm.Is 0 ohm not a short?If the meter did NOT swing over to 0 ohm that would be a high resistance indicating a open circuit and that would mean that the short is not detected at the lower voltage green setting ,the short is only detected at the higher voltage or red meter setting?
Ok I get it now I forgot the meter reads ohm differently between green mode and red mode, Maybe a digital meter will be less confusing.Sorry I got everyone upset,kick me.lol.
High voltage causes some leakage current between the live and ground, as a result, the reading can be obtained in Megaohm. However in the low voltage mode, the open voltage is about 5 volts, such voltage couldn't "drive" the leakage current to be flown, therefore, the reading couldn't be obtained
Another interpretation: At the low voltage mode, the range is in few kilo-ohms. However, when there is a fault, it sometimes has a reading of 0.1-1 Mega ohms. Therefore, the meter reading is "infinite". However, in the high voltage mode, the range is in mega-ohm order. Such fault, which is generally assumed to be 0.1-0.9 Mega ohms, can be obtained by the meter in the high voltage mode.
ei technical people.. can i ask what is the least or range value in Megs the motor should have for it to be Workable. (or lets say still in good condition).. sorry for my english... lol..
+Romeo Jr. Dacuno Phase to Ground = OL or OPEN Phase to Phase = OL or OPEN Phase A start coil to Phase A end coil = Resistance Phase B start coil to Phase B end coil = Resistance Phase C start coil to Phase C end coil = Resistance Any other thing readings than the ones above is a result of a Bad motor or Transformer.
Yeah. Nice addition to an ordinary multimeter. Got two. A fairly modern late 80es original Megger and a vintage local made. Btw. a little chicken aren't you? ;D Voltage might be high but amperage is quite low. I'd just hold the probe and wires in one hand on that occasion (as it's not connected to mains). Or you could put the crocodile on the wire and the probe to the motor chassis - it's easier :)
Order a replacement motor ASAP, and then have a candid discussion with the managers about the cost of downtime for this particular machine, and the wisdom of keeping a spare motor (as well as other critical parts for this machine) on hand. There is no "quick fix" for your problem.
Orange button need to be "hands free" like mine. So much easier. Also when it swings to the right, it's it actually zero? Or say 10K? Which would still work (although not healthy)
+james randolph Insulation has a specified temperature, humidity, voltage and current rating. At a low voltage we are not stressing the insulation. At a high voltage, if the insulation is bad, we will detect low resistance or a short to ground. Motors that are being controlled by Variable Frequency Drives are not being fed straight AC voltage. They are being fed AC voltage plus a PWM high DC voltage as well. This is what will stress the insulation and if the insulation is bad, will cause the VFD to fault out on overcurrent or phase fault.
used on a low setting "lower test voltage from the megger" the insulation in the motor is not leaking current to the motor frame ,, but higher setting (higher voltage supplied during the test from the megger) the insulation cant handle the extra electrical "pressure" and a weak spot in the winding insulation will allow a "leak" to the motor frame "the megger stress tests the insulation under higher voltage to reveal the fault that does not show up with a normal low voltage ohm test.. an important note with a megger ,, make sure you don't test circuits through a motor start or run capacitor on high voltages or one will ruin the device.
Oftentimes you don't have access to stuff like that on the job site - especially when working on the motor of a piece of machinery. The jaws of the clip penetrates the paint anyways.
Hi, it's simple. If it failed on painted motor. it will fail on bare body. Yes, off course you're right, working with clean motor body is the best way :)
well we indians we learn things earlier than you people , so i need not to make any effort . that i had in my class 5 ..... and now i am a marine engineer ..... well you people need to improve on grammar and etiquette.
Tom Jerry S.Storm( Blackfoot) I have seen bad times also, but now hope to finish up my electrical engineering degree in a couple of months. So that my kids can have better but not forget who they are.
The best I've seen and heard so far notably on the How the low voltage setting differs from the high voltage setting for fault detection and its effect on the needle sweep This truly makes the Megger unique
Thank you for the video, It just goes to show how important it is to use a meg ohm meter. Any tech who doesn't use one is a disgrace!
Halfway through I was saying "Such a fault would show up with a common DMM!". Ha!
Very good explanation of HV insulation testing and its value.
Still valuable 5 years on (and for as long as we'll be using induction motors...)
reviving a very old vid! thanks for the info. I was just given an old crank megger and wanted to see how they work.
The low voltage used by a standard multimeter in the "resistance" mode may not detect certain insulation breakdown faults like a megger will. The difference has to do with the non-linear behavior of insulation faults: they don't exactly follow Ohm's Law (current proportional to voltage) like a conductive connection does. Compromised winding insulation may register as "inifinite" ohms (open) when tested with low voltage, but will "break down" and conduct when subjected to a greater voltage.
Very good point -- ground faults don't blow fuses in ungrounded systems! Thanks for the clarification.
Best explanation on youtube for this testing.
"Ground resistance" in a power system usually refers to the low expected resistance between the grounding conductor and earth ground. This is different from insulation resistance which is expected to be very high.
That's a very good explanation. Thnx.
Very well illustrated and described. Thanks much!
Thank You for the demonstration!
A fuse or breaker will most often trip on a wye connected transformer, however on a delta-delta connected transformer it will not trip, instead you will have one leg (on a 3-phase) with no or very little voltage and the other two phases (lest say its a 3 phase 480v system) would read 480 volts to ground rather than phase to phase. just thought I would point that out to all the troubleshooters out there.
Very good demonstration thanks
Similar to a Dielectric Withstand Tester aka Hipot. What is used to detect phase to phase faults?
What type of chemical do they put on winding
.you on the copper Waring inside of a electric motor winding such as a Armature also a stator
Good & useful device. My concern is knowing which setting to use. Use the 500V & up for high powered motors & 100V or lower for low powered motors, the right?
The test voltage should go up with the devices voltage.
1/4HP motors can be made 120 volts, 240 volts, 480 volts
One tests the higher voltage units are a higher voltage.
Thus a 2HP motor for 120 volts can be tested at a lower voltage than a 1/4HP motor for 480 volts
electrical-engineering-portal.com/measurement-of-insulation-resistance-1
A faulted motor winding may act like this, but it's unlikely. The voltage output by an inverter even at low speeds will likely cause excessive current with a faulted motor winding. There isn't any harm in doing a megger check of the motor (be sure to disconnect it from the inverter first!), but the problem most likely lies elsewhere.
Nice video, keep them coming. Thanks
Thank you in advance ! How do you test phase to phase ?
Is it also possible that you can demonstrate how to perform the "No-Load Test (AC or DC)" , Load Point Test (AC or DC) & Locked Rotor (AC) on motors. bdw, thanks for sharing the video.
So should we connect the plus end of the megger to the body or to the winding? so how should the correct polarity be?
You can connect anyway.
How many volt exactly is your low voltage?
I’ve got two words for you.... Alligator Clips! Way safer friend
I just lick the wires to make them stick together
Often, it will trip the overcurrent protection device (e.g. breaker or fuse) if the fault is phase-to-phase. A ground fault on its own may blow the fuse or trip the breaker, but only if the three-phase power system is hard-grounded (e.g. a Y-connected source with the center point firmly bonded to earth ground).
I have been using a 500v megger on 240 and 380 volt motors for years without problems (though i am not an expert on this)
Just be careful there are no temperature sensors or thermistors in the winds as these will fail if tested to such a high voltage.
awesome learning. i have an interview soon! hope I do good.
A motor that shiny was either connected wrong or someone turned the overloads up... Good video.
ground resistance and insulation resistance what is the difference or is it the same? sorrry for my question thanks
A good motor would be over 20M ohm, may even be in the Giga ohm range.
A motor that has damp in the windings would probably run ok if it was over 1.5M ohm and then dry out as it warmed up. It depends on the supply voltage the motor is designed to run on a bit, this is for 240V 50hz motors.
Thankyou. Helps greatly with my studies.
That meter is a fantastic bit of kit, a generic copy of the Robin / kewtech from the 80s/ 90s. There now made by a number of manufacturers and use different brand names Fad demo and video
Thanks a lot man ! clear as water!! that was bad ass.
use ohms resistance check between winding should be the same resistance between L1 L2 L3
How do i megger a 3 phrase motor connected to vfd?
Pls can ou do a video on that.
What is the voltage of vfd
if you find an electric motor that has very low resistance using Megger test, what are the things to be done?
Recovery Files . Unless the fault is in the terminal box, you'll just have to replace the motor Or get the motor rewound.
WOW. very clear!!!
Joe Cast
Joe Cast good
I saw my megger hit 25 on a motor tht a vfd wouldnt run...wodyou replace the motor?
Great video 👍
I just want to clarify something, which somehow has to do with IR testing. If a windings resistance testing fails, the insulation resistance test must not be carried out. Is this true ?
Great explanation. Thanks!
Is there any way to check if a motor capacitor is good or bad?
Looking for megger in salutation check on a DC motor. Help please.
Im confused;At the high voltage setting the tester shows a short 0 ohm to ground and the short is detected.On the lower voltage or green setting the tester shows 0 ohm too.Does that not mean that even on the green setting lower voltage the short is still picked up by showing 0 ohm.Is 0 ohm not a short?If the meter did NOT swing over to 0 ohm that would be a high resistance indicating a open circuit and that would mean that the short is not detected at the lower voltage green setting ,the short is only detected at the higher voltage or red meter setting?
Ok I get it now I forgot the meter reads ohm differently between green mode and red mode, Maybe a digital meter will be less confusing.Sorry I got everyone upset,kick me.lol.
What symptoms would this ground faulted motor exhibit?
Eventually, after insulation has broken down, it would short to ground.
thanks sir.
Can i use a 500 V megger to a 220 or 380 rated motor???
Yup.. When on the low setting but not on high.. Y?
HI,how could i come to know that the MEGGER which i a using is working normally,reply....thankyou
Why is the ground fault only detected on a high-voltage mode? Is there a reason to this?
Many thanks!
High voltage causes some leakage current between the live and ground, as a result, the reading can be obtained in Megaohm.
However in the low voltage mode, the open voltage is about 5 volts, such voltage couldn't "drive" the leakage current to be flown, therefore, the reading couldn't be obtained
Another interpretation:
At the low voltage mode, the range is in few kilo-ohms. However, when there is a fault, it sometimes has a reading of 0.1-1 Mega ohms. Therefore, the meter reading is "infinite".
However, in the high voltage mode, the range is in mega-ohm order. Such fault, which is generally assumed to be 0.1-0.9 Mega ohms, can be obtained by the meter in the high voltage mode.
The insulation is only good for low voltage. At high voltage it breaks down.
Skimtar
Thanks For The Video partner ! Your An Angel !!!
Great work it helps in understanding ..... NICE
Good stuff! Helped me out.
Great vid!!
@nahroyo .....Ho would you go about this?
ei technical people.. can i ask what is the least or range value in Megs the motor should have for it to be Workable. (or lets say still in good condition).. sorry for my english... lol..
what is the required resistance if that motor is good?
up to Mega-Ohm or even Infinity between phases and phases to ground
+Romeo Jr. Dacuno Phase to Ground = OL or OPEN
Phase to Phase = OL or OPEN
Phase A start coil to Phase A end coil = Resistance
Phase B start coil to Phase B end coil = Resistance
Phase C start coil to Phase C end coil = Resistance
Any other thing readings than the ones above is a result of a Bad motor or Transformer.
+edge. shouldn't phase to phase have resistance because they have common point connection.
@@MR-nl8xr Yes, low resistance. The bigger the motor the lower the resistance.
@nahroyo ....Thats fantastic! Your a star!
Thans you very much
Thank you!
Yeah. Nice addition to an ordinary multimeter. Got two. A fairly modern late 80es original Megger and a vintage local made.
Btw. a little chicken aren't you? ;D Voltage might be high but amperage is quite low. I'd just hold the probe and wires in one hand on that occasion (as it's not connected to mains). Or you could put the crocodile on the wire and the probe to the motor chassis - it's easier :)
Order a replacement motor ASAP, and then have a candid discussion with the managers about the cost of downtime for this particular machine, and the wisdom of keeping a spare motor (as well as other critical parts for this machine) on hand.
There is no "quick fix" for your problem.
Orange button need to be "hands free" like mine. So much easier.
Also when it swings to the right, it's it actually zero? Or say 10K? Which would still work (although not healthy)
Thank you for the video
Good and useful device
Good video.
Always enjoyed this vid
Ive watched this video and its got me confused why would the megger read it as an open circuit when on the low setting but not on the high
+james randolph Insulation has a specified temperature, humidity, voltage and current rating. At a low voltage we are not stressing the insulation. At a high voltage, if the insulation is bad, we will detect low resistance or a short to ground. Motors that are being controlled by Variable Frequency Drives are not being fed straight AC voltage. They are being fed AC voltage plus a PWM high DC voltage as well. This is what will stress the insulation and if the insulation is bad, will cause the VFD to fault out on overcurrent or phase fault.
used on a low setting "lower test voltage from the megger" the insulation in the motor is not leaking current to the motor frame ,, but higher setting (higher voltage supplied during the test from the megger) the insulation cant handle the extra electrical "pressure" and a weak spot in the winding insulation will allow a "leak" to the motor frame "the megger stress tests the insulation under higher voltage to reveal the fault that does not show up with a normal low voltage ohm test.. an important note with a megger ,, make sure you don't test circuits through a motor start or run capacitor on high voltages or one will ruin the device.
In simple words there wasn't enough voltage to get a good reading.
thnxs bro
have some more videos
on magger
That's why analog meters are called "waggers".
thanks!
A painted motors hoist point is hardly a 'good ground'... would need to clean the paint off or even use a piece of copper tube as a ground source.
Oftentimes you don't have access to stuff like that on the job site - especially when working on the motor of a piece of machinery. The jaws of the clip penetrates the paint anyways.
@nahroyo ....Yep! Your a star!
good. Thanks
GOOD VIDEO
good work po :)
Very glad
A painted motors hoist point is hardly a 'good ground'... would need to clean the paint off.
Hi, it's simple. If it failed on painted motor. it will fail on bare body. Yes, off course you're right, working with clean motor body is the best way :)
There is no such thing as a "Meggar insulation test" Meggar is a brand of electrical testing gear.
N0 Megger is a brand name. Meggar sounds like a lizard of some sort.
Nice
dear,,btc.your video looing good inough ,next time i wil visit again.tk.s so loong.
Plz in Hindi language
thats fucked up
Turkce anladsana megeometir sail ulanylya
Have you ever put the clamp on your pecker and the probe on your balloon knot ? You have not lived sir until you have given that one a whirl !
+tjk. did you really try that.
Yea, it happened to me! I bought this same device from a Chinese website advertised as a penis enlarger.
fed up of us accent ............. dat person shud learn english frnst
I would rather listen to this guys accent than read your terrible grammar!
it needs spoken english to communicate , i am an Indian so my grammar is pretty better than anyone around the globe
I doubt your grammar is better than mines! But I'll give you points for learning English! At least you're making an effort!
well we indians we learn things earlier than you people , so i need not to make any effort . that i had in my class 5 ..... and now i am a marine engineer ..... well you people need to improve on grammar and etiquette.
Tom Jerry S.Storm( Blackfoot) I have seen bad times also, but now hope to finish up my electrical engineering degree in a couple of months. So that my kids can have better but not forget who they are.
You need a low ohmmeter to test that motor
awesome learning. i have an interview soon! hope I do good.