exactly a week ago one of my compresor motors went down; 1700 HP, 6300 Volt, 2 poles
as I could not perform an on-line ESA / MCSA I grabbed my off-line MCA instrument and off I go;
Result of the low voltage testing:
- possible overheated winding
- check impedance and inductance pattern:
pattern shows possible rotor damage
- no obviouse short circuit; Fi, I/F and ground
resistance O.K.
(see attachment)

next step: I performed an off-line inductance rotor test: non conclusive (see attachment)

I dismanteled the motor: an obviouse short "turn to turn" (pictures in the attachment)

Why did this short not show up ? Why did the rotor test fail ?

How reliable is the low voltage winding testing ?

HELP is apreciated

MOGLI

REPORTE_MCA_y__Rotor_Test_Compresor_1700_HP.pdf (643 Kb, 143 downloads)

MOGLI,
I AM NOT THAT FAMILIAR WITH ALL-TEST, BUT IT DOES APPEAR TO SHOW SOMETHINGS NOT RIGHT WITH THE POWER CIRCUIT. (RESISTIVE IMBALANCE IS >3%, IMPEDANCE IMBALANCE ? IS > 5%). IS THE ROTOR TEST SIMILIAR TO THE PdMA RIC TEST? IF SO, IT APPEARS TO BE A LOW INFLUENCE ROTOR. CAN A CASE BE MADE FOR THE "TWO PHASES DOWN, ONE UP" PATTERN? IF THERE IS A STATOR FAULT (SUCH AS A SHORT) THE ROTOR TEST WILL NOT BE ACCEPTABLE. WHAT DOES YOUR TREND DATA SHOW? I AM LOOKING FORWARD TO OTHER POST BY SOME OF THE FORUMS MORE EXPERIENCED MEMBERS(EPETE, MOTORDOC, ETC...); BUT WANTED TO THROW MY THOUGHTS OUT.
THANKS, JEFF

I can sense frustration from your post. However one should not be too surprised by not finding a turn to turn short with low voltage tester.
If you calculate what voltage you will impress on the turn to turn insulation with your 9 Volt tester, you will find out that it is something like 50 millivolts (I have calculated it somewhere in the past).
Anybody who has ever held a voltmeter in his hand has to laugh at such a voltage. Just try to take a reading with your Fluke voltmeter on a 1.5 Volt battery. If you really want to get a reading, you have to press the test leads very firmly to break the layer of oxide on the surface of the metal contacts of the battery. And this is 1.5Volts!
In your case you want to analyze with 0.050 Volts a turn to turn short. In the damaged area there was all kind of arcing, heating and oxidizing. Unless the turns welded together, you do not have a chance with your millivolts. Yet use the surge tester and you will find immediately what is going on!
Your MCA tests results are also interesting: The resistive imbalance is 3.21%. The inductive imbalance is 4.82%. Yet the impedance imbalance is 36.62%. Considering that the impedance is: Z= sqrt(R^2+X^2), the result is really puzzling. (X=2*pi*f*L).
Taking into consideration all the above, you are probably using a wrong technology.
jank

Thanks for sharing that case. Out of curiosity, how did you conclude turn-to-turn short. Is there molten copper? Or just the fact that a fault happened far out on the knuckle where there is assumed no ground plane close or other phase (adjacent knuckle) close by. To what do we attribute burning on that phase at those three locations... very high current in that phase?

I am not at all familiar with the All Test Pro equipment. Like Jan, the data doesn't make sense to me.
R = 0.698 0.674 0.718
|Z| = 140 75 140
L = 27 29 27
Phase Angle = 83 83 83

I am utterly unable to construct any vector diagram that would match this data (using the relationship Z= R+jwL). It would be educational if someone familiar with this equipment could show us a vector diagram or explain for us how this data is self-consistent. The conflict that I see I think is the same as Jan, but let me say it a different way. As a rough approximation, the phase angle close to 90 tells us the impedance is primarily inductive and so the ratio between the three impedances should be not too far from the ratio between the three inductances. But the inductances are balanced much closer than the Z. Already it doesn't make sense. The only possible explanation is that the imbalance comes from the R. And it must be a very very dramatic imbalance in R since R has relatively little effect on a primarily-inductive impedance. But no... the resistance are balanced much closer than the Z also.

Can someone explain it? What is the frequency associated with this test data?

Another question I have about the All Test Pro is this I/F test. It doesn't seem to have shown anything on this machine (48 48 48). But I would never condemn a test based on one machine (I think almost any test out there can be fooled in one case or antoher).

But shouldn't the I/F logically be a subset of the results seen on Frequency Response Analsyis testing of transformers? FRA is a test has been studied and documented in many papers and is becoming more and more widespread. But strangely enough, they view it as a test primarily to detect winding movement (not turn shorts). Detection of turn to turn fault is rarely discussed in connection with FRA. Transformer turns ratio is the primary tool for detection of turn shorts in a transformer. But TTR relies on current flowing through the short. If the I/F and frequency response provides an ability to somehow see the latent turn-to-turn flaw before it becomes a short (and therefore before the TTR can see it), then why aren't the transformer guys talking about this aspect or using this aspect of the FRA test?

This message has been edited. Last edited by: electricpete,

Mogli

Jeff4 is correct. The impedance and inductive patterns indicate overheating of the insulation system. As you know, impedance consists of resistances, capacitive reactance and inductive reactance. Overheating or damage to the insulation system will cause a change in the capacitive reactance of the circuit.

The unbalanced inductances indicate that something has occurred with the phases, as well.

I am surprised that the phase angle and current/frequency response did not detect an inter-turn short. Do you have a picture of the actual fault point (where it has shorted) as what I see is mechanical damage to the insulation system. The times I have seen this type of situation, there is usually just a portion of the insulation of an individual conductor that has shorted to ground, and not between conductors. The I/F and Fi are normally affected when there is inter-turn failures.

Howard

[QUOTE]Originally posted by MotorDoc:

The impedance and inductive patterns indicate overheating of the insulation system.
__________________________________________

The inductive imbalance is in green, yet you say that there is an indication of overheating. The winding does not seem to be over-heated from the pictures. How would overheating change the reactance? (See the next sentence first!)Explain!
The winding seems to be pretty even as far as the color is concern. If it were overheated it was overheated evenly with the exception of about 4 short spots. No reason for any unbalance!

quote:_______________________________________________
As you know, impedance consists of resistances, capacitive reactance and inductive reactance. Overheating or damage to the insulation system will cause a change in the capacitive reactance of the circuit.
_________________________________________________________________

Everybody knows, that the temperature will change the properties of any material. If you say that the capacitive reactance has changed, say also by how much! Did the permitivity of the insulation changed from 4 to 64 or 256? If you do not know how much, you should not have said anything! Now is the chance to explain. I have heard that “something has changed” without explanation too frequently from you and other low voltage proponents.

quote:_________________________________________________________
The unbalanced inductances indicate that something has occurred with the phases, as well.
_________________________________________________________________

We could have all seen that something indeed happen. The motor has failed turn to turn in the knuckle. That is what the picture shows. But your gadget basically shows that nothing happened: little resistive imbalance (in green), little inductive imbalance (in green), no phase imbalance, no I/F imbalance. I discount the impedance unbalance because you cannot explain it (maybe just a glitch?).

quote:_____________________________________________________________
I am surprised that the phase angle and current/frequency response did not detect an inter-turn short.
_________________________________________________________________

I am not surprised at all! That motor is 6300 Volts line to line. Somebody used your gadget of 9 Volts RMS and did the ” testing” according to the instruction manual.
Just imagine that you are in business of making the pressure vessels. You have just finished one for 6300 PSI pressure. You are in process of testing the vessel. So you intend to impress pressure of at least 9000 psi an check for leaks. But all of a sudden an expert appears saying: 9000 psi cannot test your vessel, you have to go to 9 psi and it will tell you everything!
You will listen to him politely and when he is persistent you will throw him out of the door (closed).
Incredibly it will not happen when the electricity is involved!


quote:____________________________________________________________
The times I have seen this type of situation, there is usually just a portion of the insulation of an individual conductor that has shorted to ground, and not between conductors.
____________________________________________________________________

The insulation resistance to ground is >99 Mohms. Your gadget clearly shows that. There is no ground. And even if there were one, it would not matter. The test was performed “ line to line“, not ”line to ground”.

jank

Mogli

I will contact you via email on Monday.

Howard

DrPenrose
the same kind of thing i m experiencing during the motor testing .
WAT IS YOUR RECOMMENDED METHOD TO FOR DOIN ROTOR TEST. ALSO WOULD LIKE KNOW WATS YOUR RECOMMENDED TOLERANCE LEVEL?
I CHECKED THE INSTRUMENT ON THE SAMPLE MOTOR PROVIDED BY ATP. AT POSITION 2 WHICH IS T TO T SHORT BUT DURING TEST WITH ATP IV IT SHOWING ONLY IMPDENCE UNBALANCE,INDUCTANCE UNBALANCE . I/F AND FI ARE UNDER ITS TOLERANCE. HOW ANY ONE CAN CLARIFY IS IT T TO T SHORT OR WINDING CONTEMINATION????

JUST WOULD LIKE TO KNOW THE EXACT DATA ENTIPRETATION OF TESTING.
I ALSO WOOULD LIKE TO HAVE YOUR EMAIL ID IF POSSIBLE.
THANKS & REGARDS

Level1

My email is howard@motordoc.com

As an FYI, I am not with ATPro. However, I am very familiar with the product as I was the GM from '99-'04. I continue to do training on all of the motor diagnostic technologies including ATPro, Baker, Areva, PdMA, etc. I am also the Executive Director of the end-user driven Institute of Electrical Motor Diagnostics, Inc. who is working on the development of the certification programs for electrical motor diagnostics with ANSI and ISO.

Now, as far as the demo motor - the M2000, it is a 'training' motor which has a modified electronic package to simulate different types of problems. The interesting thing about the training motors is that up to early 2001 the motors were almost identical. After that point, the motor manufacturer moved their plant to another location with lower labor costs. From that point on, the motors would test dramatically different making it more and more difficult to 'tune' the training motors to work with the instruments.

To my knowledge, the ALL-TEST IV PRO 2000 platform (electronic package and EEPROM) has not changed since 1997. As long as things are continuing correctly, the tests are NIST traceable and during the time I was there, we would be able to get identical results from any two instruments. I can only assume that things have not changed. The low voltage technologies used by ATPro and PdMA and online technologies, including electrical signature analysis, motor current signature analysis and torsional analysis are covered under IEEE Std 1415-2006, including pass/fail values.

As far as the problem that MOGLI is experiencing, the Fi and I/F change when there are changes to the capacitive reactance between conductors, such as carbon tracking. A 'hard short' results in changes to all of the test results. What is interesting, in this case, is that it appears that something occurred on the outer skin of the knuckle of one coil. The question, because the I/F and Fi did not change, was where the location of the short occured. In all of the cases where the technology has resulted in unusual answers, such as the report at the beginning of this string, there has been a logical answer. What I am expecting to see is that something outside came into contact with a single conductor, or the outside of two conductors, or something else similar which did not cause a change to the insulation between conductors. I would have suspected a broken conductor, or two, however, I would also have expected to see a sizeable difference in the resistive balance. Without knowing the circuit in this motor, I would keep that as a possibility.

As outlined in the IEEE Std 1415-2006, as well as work on machines of all sizes and voltage, a 'collapsing' impedance as it relates to inductance means that there has been a change to the dielectric (electrical insulation). When you send me your question via email, I will also include a paper on the reactance changes to the insulation system.

I do prefer answering these questions on this forum. I am more than happy to answer those questions via email. Unfortunately, it also means that others do not get the benefit of the explanations.

Howard

[QUOTE]Originally posted by MotorDoc
__________________________________________________________________________
Now, as far as the demo motor - the M2000, it is a 'training' motor which has a modified electronic package to simulate different types of problems. The interesting thing about the training motors is that up to early 2001 the motors were almost identical. After that point, the motor manufacturer moved their plant to another location with lower labor costs. From that point on, the motors would test dramatically different making it more and more difficult to 'tune' the training motors to work with the instruments.
________________________________________________________________________

Response:
The idea of tuning the motor to the testing instrument is utterly ridiculous. The variations of the motor failures are absolutely limitless. If you have to tune a “training” motor to your instrument, how do you expect to test all the “un-tuned” motors in the field?

quote:_____________________________________________________________________
As outlined in the IEEE Std 1415-2006, as well as work on machines of all sizes and voltage, a 'collapsing' impedance as it relates to inductance means that there has been a change to the dielectric (electrical insulation).
_________________________________________________________________________

Response:
There are 3 wires sticking out from the Mogli’s motor, phase A, B and C. The only possibility to test the impedance is by connecting a power source to two of those 3 wires, record the voltage and record the current (then you repeat it 2 more times). From the known voltage and the current you can calculate the impedance Z=V/I.
The impedance of the circuit is:

Z= sqrt[ R^2 + ( Xl- Xc)^2].

R is resistance, Xl is inductive reactance, and Xc is capacitive reactance.
By MEASUREMENT only, it is IMPOSSIBLE (I repeat: IMPOSSIBLE) to separate the inductive reactance and the capacitive reactance. In order to arrive at different impedance if the inductive reactances (or the inductances) are equal (as in the Mogli’s case), they would somehow gain the knowledge of the capacitive reactance. (Please note that the resistances are very close enough not to play any role.)

BUT !!!:
1) It is IMPOSSIBLE to MEASURE the turn-to-turn capacitance (however it is possible to calculate that from the dimensions).
2) It is IMPOSSIBLE to measure the capacitance to ground separately for each phase on an ASSEMBLED motor with 3 wires out only.

In other words, they only had one chance of calculating the inductance: By neglecting the resistance, as it is being done every day with only a tiny error. Somehow the error in their case was approaching 50% (see 140 Ohm and 75 Ohm). And if they somehow managed to gain the knowledge of the capacitive reactance, how did they find the inductive reactance only? (Please answer this one!)
There will be no answers to any of those above questions, period.
Any answers are given only to people who know less than they do, and it is done over a private E-mail.

quote:____________________________________________________
When you send me your question via email, I will also include a paper on the reactance changes to the insulation system.
___________________________________________________

Response:
He can post the “paper” on the net just as good as E-mailing it to you. I bet the “paper” has been posted several times already.

quote:____________________________________________________________________
I do prefer answering these questions on this forum.
_______________________________________________________________________

Response:
So please, do!

jank

I think it's a great discussion by all and I hope it continues.

I will repeat that I have never even laid eyes on an All Test Pro test box. But I am very curious to understand the claims. I would also like to see the questions discussed here for everyone's benefit. Clearly there are differences of opinion, but in my opinion it is healthy to discuss those differences of opinion help clarify the picture, rather than to simply ignore the differences of opinion. Also I am personally less inclined to believe a claim when those that make the claim won't answer questions or address objections.

Question EP1 - Is it correct that the R, L, Z, and Fi measurements for a given "phase" (i.e. T1-T2) all come from a single measurement of voltage and associated current under single-frequency sinusoidal excitation?

Question EP2 - What is the frequency used for this measurement? (R, L, Z, Fi.....not I/F).

If the answer to question 1 is yes as I suspect, then the only info available to the test box is an impedance magnitude ( |Z|) and an impedance phase angle (Fi) We can transform those two variables into another set of variables resistance R and reactance X using R = |Z| cos (Fi) and X = |Z| sin (Fi)

And we can transform the X into an equivalent L or C using frequency. For arguments sake, assume as Howard has indicated that the capacitive reactance effect in this circuit is not negligible. Then the X is a combination of the of inductive reactances and capacitive reactances. Assuming the inductive reactances dominates the combination, we can calculate an apparent inductance as follows:
Lapparent = X/(2*pi*f)

The Lapparent is a function of the true inductive and capacitive elements of the motor. But assuming the answer to question 1 is yes, the test box can't discriminate between those and it doesn't know anything about them. All it knows is Lapparent which it would report as L.

This leads back to the question of my previous post, amended slightly to change L into Lapparent:

Question EP3: Are there any coherent set of circuit parameters Ra, Rb, Rc and Lapparent_a, Lapparent_b, Lapparent_c which would create the reported values of Za, Zb, Zc, Lapparent_a, Lapparent_b, Lapparent_c, Ra, Rb, Rc, Fia, Fib, Fic?

(Using the known relationship Z=R + j*2*pi*f*Lapparent, these data don't seem self-consistent to me.)

Now on a different subject:

quote:

motordoc 04 November 2007 08:45 AM
The low voltage technologies used by ATPro and PdMA and online technologies, including electrical signature analysis, motor current signature analysis and torsional analysis are covered under IEEE Std 1415-2006, including pass/fail value

IMO, the most surprising claim for the All Test Pro is that the I/F test can detect "developing" turn-to-turn shorts before they happen as Howard has claimed many times. So, I looked with interest to see if IEEE1415 supported this claim as might be inferred from the above comments. What did I find to support that claim? Absolutely nothing!. All the standard does is list the test, say how to perform it, and list some limits. But the standard doesn't even mention what the test is supposed to accomplish! It doesn't even MENTION the term turn-to-turn shorts in connection with I/F test (they call it variable frequency test). In contrast, the standard IEEE 1415 tells us directly that surge test is performed as a check of the turn insulation. (search your standard for "turn" and you will see it pulls up many times in connection with surge test but not one single time in connection with I/F). So, IEEE 1415 is acknowledging that there is a test out there offered by a vendor, but they won't go out on a limb to even mention what it's supposed to detect? Doesn't sound like an overwhelming endorsement to me.

Now on table 1 of IEEE 1415, in the row for Variable Frequency (I/F) test, they list a reference to IEEE 389. One assumes since they haven't even told us the purpose of this test, that IEEE 389 will reveal the purpose. I looked up IEEE 389-1996 section 11. It begins by giving an overview of the test an it's purpose:

quote:

IEEE 389 (1996) – "IEEE Recommended Practice for Testing Electronics Transformers and Inductors"
Section 11.1 "Transformer frequency response"

When transformers are designed to operate over a fairly wide range of frequencies and serve the function(s) of matching a load to a power source with a linear response over that range, to provide voltage isolation between source and load, or to provide rejection of common-mode voltages between source and load, such transformers are usually tested to determine their frequency response characteristic over a specified range when operated in an amplifier circuit for which they were designed. Also, where transformers are used in control systems, the transformer frequency response is often valuable in evaluating the stability and other dynamic properties of the control system.

Note that this applies to electronic transformers that are subjected to a range of operating frequencies. The test description shows the purpose of the test is simply to ensure the transformer output characteristics remain stable over this range of frequencies. It is natural to wonder about this because the response will be affected at low frequencies by saturation effects and at high frequencies by leakage reactance effects.

I don't see any discussion whatsoever connecting this test to the detection of existing or developing turn to turn faults. In fact the whole section 11.1 doesn't even mention turn to turn faults. So if I read the entire body of IEEE guides/standards referencing motor variable frequency testing (I/F test) – namely IEEE1415 and the referenced IEEE 389 - the only thing I know about the purpose of the Variable frequency test is that it's supposed to check that transformers perform satisfactorily over a frequency range?

So why didn't IEEE 1415 tell us that the I/F (variable frequency) test is supposed to detect developing turn shorts (or any type of turn faults for that matter)? I guess it could have been a simple oversight. Hmmm, but Howard has told us how many multiple reviews and drafts were made, so I find that very hard to believe that the committee including vendors would "forget" to describe what the test is intended to do. On the other hand, I can easily imagine that if vendors were clamoring to put in a test but the technically-oriented members weren't convinced of it's effectiveness , this type of wording would be the type of meaningless compromise that might be reached in a committee environment to satisfy everyone. The commercially-oriented IEEE members can go out and proudly proclaim that their standard is "covered" (with the implication that it is somehow endorsed). The technically oriented IEEE members don't make any claim whatsoever about what the test would accomplish. This is pure speculation on my part. After all I wasn't there... maybe there is some other logical explanation. Howard was there, maybe he can explain it for us.

question EP4 – Why doesn't the IEEE 1415 even bother to tell us what the variable frequency (I/F) test is supposed to accomplish?

And now that we have seen how utterly unconnected the IEEE389 standard is from I/F testing for developing motor shorts, some of the quotes we have seen before become even more curious. This IEEE 389 is the exact same standard that Howard himself has cited at least twice as "validating" the I/F test:

http://www.reliabilityweb.com/excerpts/excerpts/low_voltage.htm

quote:

"Low Voltage Vs High Voltage Testing" by Howard Penrose
IEEE Standard 389-1996 is the IEEE Recommended Practice for Testing
Electronics Transformers and Inductors. This is one of the more important standards relating to MCA. Table 1 of the standard provides the recommended tests and specifications for transformer and inductor groups. It also covers impedance and reactance limits as well as conductor resistances. Then, discussed under General Test Methods – Surge Testing -“The test itself is destructive.” Section 6 discusses simple DC resistance tests and limitations. Sections 8 through 11 cover the meat of MCA testing: Section 8.1.1 – calculating winding ratios with inductance. This section was interesting as we had issued a test procedure for transformer testing which required the user to short and ground all of the leads opposite of the side being tested. Standard 389 specifically outlines the same procedure; Section 8.1.2 – Transformation ratio with by impedance measurements; Section 8.3 – Impedance unbalance methods and limits; Section 8.4 – Phase balance tests and limits; Section 10 – Inductance measurements by impedance bridge method; and, the truly interesting find – Section 11.1 – The transformer frequency response, which outlines test methods that validate the Current /Frequency (I/F) test method.

Apparently you felt strongly about it, because you wrote the same thing in another place:

quote:

"Motor Circuit Analysis Standards" by Howard Penrose
http://www.irisgroup.org/downloads/Motor_Circuit_Analysis_Standards.pdf

"IEEE Standard 389-1996 is the .IEEE Recommended Practice for Testing Electronics Transformers and Inductors.. This is one of the more important standards relating to MCA . Table 1 of the standard provides the recommended tests and specifications for transformer and inductor groups. It also covers impedance and reactance limits as well as conductor resistances. Then, discussed under General Test Methods . Surge Testing - .The test itself is destructive.. Section 6 discusses simple DC resistance tests and limitations. Sections 8 through 11 cover the meat of MCA testing using ALL-TEST style methods: Section 8.1.1 calculating winding ratios with inductance. This section was interesting as we had issued a test procedure for transformer testing which required the user to short and ground all of the leads opposite of the side being tested. Standard 389 specifically outlines the same procedure; Section 8.1.2 . Transformation ratio with by impedance measurements; Section 8.3 . Impedance unbalance methods and limits; Section 8.4 . Phase balance tests and limits; Section 10 . Inductance measurements by impedance bridge method; and, the truly interesting find . Section 11.1 . The transformer frequency response, which outlines test methods that validate the ALL-TEST patented Current /Frequency (I/F) test method.

Here the test is not just "covered" but in fact "validated"! And it was not just a passing comment... it was repeated twice in web-articles published with Howard's name. So if we read the above quotes and take the author at his word, we are supposed to believe that IEEE389-1996 "validates" the I/F method which is claimed to provide early detection of developing shorts. But what is not even mentioned in the above articles is that IEEE 389-1996 addresses frequency response on transformers to ensure consistent operation over the range of expected operating frequency, which has nothing whatsoever to do with turn shorts (see excerpts and discussion above). On the surface, it has the appearance of an attempt to mislead people into believing that IEEE 389 says something that it doesn't say at all. But that's just me. Maybe I have overlooked something. Maybe Howard can provide some logical context to explain his comments.

Question EP5: Please explain why you believe that the existence of the IEEE389-1996 variable frequency test on transformers (that is intended to ensure stable operation over the expected operating frequency range) somehow validates the I/F test (which is claimed to detect developing detect turn-to-turn shorts on motors)

This message has been edited. Last edited by: electricpete,

ElectricPete and Jank

I understand that you have both have an unhealthy need to drag me into nonsensical arguements for some time, including distrupting legitimate questions within the forum.

I figure, based upon that and some of the direct and desperate methods that have used to attempt to get my attention, that there are one of two reasons for this: 1) You feel that you require my approval for some reason; or, 2) You have some other, more personal, reason.

In either case, I don't swing that way, nor have the desire to waste time.

So please understand why I am ignoring you.

quote:

I understand that you have both have an unhealthy need to drag me into nonsensical arguements

I don't think it's nonsensical to ask for an explanation of the fundamental relationship underlying L, R, Z, and Fi and a reconcilation of how that is reflected in these measurements.

I don't think it was nonsensical to ask why IEEE completely omitted the purpose of the I/F test.

I don't think it's nonsensical to ask for an explanation of claims regarding I/F that appear misleading.

quote:

So please understand why I am ignoring you.

I think everyone here is smart enough to understand perfectly why you always choose to ignore the tough questions.

This message has been edited. Last edited by: electricpete,

[QUOTE]Originally posted by MotorDoc:
ElectricPete and Jank
I understand that you have both have an unhealthy need to drag me into nonsensical arguements for some time, including distrupting legitimate questions within the forum.
QUOTE]

It is not because of you Motor Doc! Don’t be so self-centered! If I saw statements such as yours above, I would object them just as loudly even if they were coming from anybody else. It is not my fault that most of the nonsensical statements are coming from your direction. Do you remember force on bars, contraption, capacitive reactance in the motor equivalent circuit, solid rotor, the gap and of course I cannot forget the “overheating of the disconnected motor”. That one was the best!

jank

Not to throw any water on the fire - Electrical fire, not good with water, but on a side issue.

quote:

(motordo) I am also the Executive Director of the end-user driven Institute of Electrical Motor Diagnostics, Inc. who is working on the development of the certification programs for electrical motor diagnostics with ANSI and ISO.

Do you think this will lead to an ISO cerification?

quote:

R is resistance, Xl is inductive reactance, and Xc is capacitive reactance.
By MEASUREMENT only, it is IMPOSSIBLE (I repeat: IMPOSSIBLE) to separate the inductive reactance and the capacitive reactance.

Another question: You can't vary the frequency or use a special input (transient response and parameter extraction) to separate the two? Measure may be a strong phrasing, but infer or calculate?

Bill

The IEMD team is working hard with TC108/SC5/WG10 to develope the certification program. It is expected that it is still 24-36 months off still due to the politics involved in the working group and the technical documents involved. To make a very long story short, there are now several ISO groups who want to tackle the current signature/electrical signature parts. This, of course, has slowed things down, again.

The team representative has been Ken Culverson.

The good news is that ISO has sent out the certification document last week that outlines the requirements for certification. All of the voting for that ends in February, 2008. I am sending it out to the IEMD membership this week for comments.

Because of the politics and amount of time that we have been working with ISO, the membership directed us to also pursue ANSI certification directly. One or the other should occur, but will still take time.

Howard

This message has been edited. Last edited by: MotorDoc,

One must use care when talking certification; ISO does not certify or authorize groups to certify. This has been a touchy subject. For instance, one should not use "ISO certified."

ISO 17024 gives some of the (gory) details of the processes involved.

Apparently, certifying bodies don't require accreditation (except for credibility) as I understand (don't quote me).

TC108 will create a document containing a body of knowledge to which one can train. I gather that someone like you (or anyone for that matter) could issue certificates if done in accordance to the training and quality standards (additionally follow the body of knowledge). It all seems rather messy to me.

I believe that ANSI is an accrediting organization, not a certifying body, but you should be able to let us know.