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500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 1:33 AM

We are having a brand new 500HP motor of Seimens which when run on no load all the parameters are normal and running fine.

But when coupled and run on load (Load= Shipping pump of crude) its speed reduces and and getting stopped.

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#1

Re: 500 HP Motor good with NO Load, but stops at load

01/10/2012 2:50 AM

What if the load is 600kw? (We don't know, no calculations having been given.)

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#2

Re: 500 HP Motor good with NO Load, but stops at load

01/10/2012 3:16 AM

If it stops, does the overload device operate or does it just sit there and make smoke?

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#3

Re: 500 HP Motor good with NO Load, but stops at load

01/10/2012 3:24 AM

Probably the load torque is more than the motor rated torque. Improper selection of motor.

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#4

Re: 500 HP Motor good with NO Load, but stops at load

01/10/2012 4:32 AM

We are actually replacing a new motor of same capacity with the existing load

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#5
In reply to #4

Re: 500 HP Motor good with NO Load, but stops at load

01/10/2012 5:46 AM

Why did you replace the motor?. Is the pump OK?.Did you check the amp drawn with nameplate amp?. Did the earlier motor take same amp?. Is the alignment OK?.Check the starter contacts,Try throttling little.

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#6

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 8:43 AM

Have Seimens been contacted? If not why not, I know they are the first people I would be jumping up and down, screaming at!

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#7

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 8:46 AM

first cheak your load....usually pumps have jamming problem due to gland,bearing and so may problems which jam the pumps rotor...if your pump is ok then change the inrush current setting from your motor control circut i.e improve starting current setting from your tripping relay

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#8

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 9:10 AM

All most sounds like you have lost a phase going to the motor.

Large unloaded induction motors will often times run minus one phase and appear to be normal. But... once connected to a load they usually will not start turning or act the way you have described, especially if there is any drag supplying torque to the motor by way of crude flowing in the system.

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#10
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 10:04 AM

This answer sounds very plausible. GA You've answered all of the symptoms with this proposed missing phase. The missing phase can be anywhere in the wiring outside or inside of the motor and can easily just be a poor connection that opens when heated.

I would put three current transformers on your three phases of power and measure with an oscilloscope what happens to the three currents with respect to line voltage as the mechanical load gets applied. This will immediately identify if you have a phase wiring failure or an excessive mechanical load. The OP must then do an appropriate tear down of the relevant parts to find out what is wrong.

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#12
In reply to #8

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 12:15 PM

So, why did the overload device not operate to protect the motor?

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#13
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 12:23 PM

Obviously I'm speculating but I have a proposed scenario. The torque required to move the load was less than the overload device would allow but more than this motor with only 2 phases could produce.

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#14
In reply to #12

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 1:52 PM

There is no mention of what the OL device did or did not doin the original posting.

I agree with you though. It is a valid question, OP... what did the OL unit do?

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#28
In reply to #8

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/12/2012 3:56 AM

Actually we are having 3 shipping pumps running parallel to it of same capacity (pump and motor).....

so we even changed the bed and connected to another pump its same issues.

other 2 motors are running fine with that pump and if we put this motor, it trips on high current of about 300Amps (it supposed to be 75Amps)....

IR and WR everything normal...

i guess something should be wrong with the winding...

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#9

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 9:30 AM

If it stops, does the overload device operate or does it just sit there and make smoke?

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#11

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 12:02 PM

North of 60 made a good point as to loss of a phase. Had this happen many times. Checking all 3 phases just like checking for a blown fuse with a voltmeter to insure proper voltage from line side to load side across different legs. Generally could always hear the difference in speed if you were nearby when you lost a phase.

Did you check to see if the specific gravity of the crude was the same as the pump-motor load was designed for or the discharge pressure didn't change. Sometimes a Process Engineer can set the parameters wrong although most installations require a 10 to 15% safety factor to allow for increased capacity. I'm more inclined to go with the loss of a phase although incorrect Overloads in the circuit can also trip the motor. Even if one of the three was too small you can have a problem.

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#15

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 2:27 PM

If there was a loss of phase BEFORE the motor was started, it would not turn at all. It would have to start turning and THEN lose a phase for that scenario to be valid.

It's much more likely that you have mis-connected the motor, i.e. it is a dual voltage motor and you have connected to the HIGHER voltage winding pattern while applying the LOWER voltage. For example, let's say it is a 690/400V motor. The Y (Star) winding pattern would be for 690V, the Delta winding pattern would be for 400V. But if you are more commonly connecting smaller motors that are 400/230V, then the Y would be 400V and the Delta would be 230V. So if, out of force of habit, you connected this motor in Y because that is how you normally connect 400V motors, then you are reducing the motor torque by the square of the voltage reduction. So effectively, you are giving this motor 58% of the voltage it expects to see, so the torque is reduced to .58 * .58 or 33% of normal torque and you effectively have only 165HP available. Unloaded it will start and run and look normal, in fact it will not trip on OL. But as soon as you apply a load, for which you BOUGHT a 500HP motor, then have only 165HP available, it slows down and stalls. But because the current is also artificially reduced to 33%, it will take much longer to trip the OL relay.

Check your motor connections again.

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#16
In reply to #15

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 7:17 PM

Yes... and no. The lost phase could turn this setup into an open delta config. Anything could happen then.

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#17
In reply to #15

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 9:10 PM

I said this earlier but I did not make a full explanation. If the OP measures in a time based method the currents and the voltages applied to the motor they can then calculate how much real power is drawn from the mains during this mechanically loaded slow down. Comparing actual power drawn with expected power drawn while a motor is obviously overloaded will show if the motor is properly sized for the actual load, if the motor is wired properly, if the motor is itself electrically failing.

When one is baffled why anything isn't working as expected, measure and analyze what is really happening before you change anything. Only once you know what you actually have instead of what you expected to have can a real, reliable repair be attempted.

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#18
In reply to #15

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 10:36 PM

He didn't mention the type of starter used or the connection.

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#21
In reply to #15

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 9:34 AM

J,

While the second half of your reply is a very plausible answer, I have to disagree with you on the first part.

"If there was a loss of phase BEFORE the motor was started, it would not turn at all. It would have to start turning and THEN lose a phase for that scenario to be valid."

I have seen many 3-phase motors start and operate under light loads with only two legs available - vacuum pumps, oil heaters, mixers, blowers for AC units...

In one instance I discovered that three 240 volt, 3-phase AC units were running on single phase power while trouble-shooting single phase devices in the building that were not working. The blowers for the AC units seemed to start up normally and ran quietly on 240 volt, 1-phase power. I would have never guessed that anything was wrong if I had not checked voltage at the distribution panel with a multimeter.

The blower overloads did not trip because the temperature in the building was moderate, so the thermostat was shutting the units off after only a few minutes of operation. If it were hotter then the blowers would have needed to run longer allowing more heat to build up.

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#25
In reply to #21

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 12:33 PM

"While the second half of your reply is a very plausible answer, I have to disagree with you on the first part."

Look, I'll acknowledge that there are exceptions to every rule, but it's never a good idea to first assume your situation is the exception, not the rule. It can lead to a big waste of time and / or compounding mistakes. The OP already has problems, he doesn't need to be chasing phantoms.

The only time I have ever seen a 3 phase motor START when there is single phase, is if some outside force was spinning the motor before it was energized. That can sometimes happen on pumps and fans if there is a common header that they feed in to so that product flow that already exists in the system is pulling the motor. But if you apply single phase power to a 3 phase motor that is not already moving, there is no relative rotation of the magnetic fields. It just sits there and vibrates back and forth.

As to the "open delta" issue, that can only happen IF the supplying power system was an ungrounded delta system to begin with. That still exists in some areas of the US and Canada as legacy systems, AND in small installations where you have a 240/120V 4 wire (Red Leg) Delta feed (which might explain your example), but that would NEVER apply to something as large as 500HP and never in a petroleum facility. For the most part new systems are Wye now in North America and everywhere else in the world. In a Wye system, there is no open delta possible.

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#26
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 1:22 PM

Point taken - power for his facility should be pretty well balanced considering his industry requirements.

I am inclined to think that the most likely problem is that the replacement motor has been miswired, but we don't really have enough data to rule out all other possibilities.

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#19

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/10/2012 10:51 PM

If the OP could perform some current measurements and share them with us it would eliminate a lot of guess work.

More information please.

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#20

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 12:33 AM

Hi Prabut29, I would have a look at your parameter settings, it sounds to me like the VSD Controlling this motor has a setting that can be set to: Increasing Speed Reducing Torque, I think that could be the problem, You Need to change this parrameter to Increasing Speed, Increasing Torque.

Check it out and let me know.

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#22

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 11:37 AM

It looks as though you might have changed the motor and that was not the problem!!!

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#23
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 11:41 AM

Could be.

Hey, where have I seen that signature before?

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#24
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 11:57 AM

I forget where I saw it some years ago, and I saw it again somewhere recently and liked it enough to copy and use......neat isn't it?

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#27
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/11/2012 7:54 PM

That's really good, Andy - congratulations.

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#30
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/12/2012 7:14 AM

Actually my youngest daughter (26) has been ambidextrous as long as I have known her(!!).

She can write with either hand, with a similar style, can write with both hands simultaneously the same sentences.

Eats with the knife and fork (together, not what the people in the US sometimes do!!) and can swap hands/implements and carry on eating and swap again.

We worked out the reasons for that go back to when she was tiny and sitting opposite me (that's important) at the table and was always asking what was the "right" way round? I was worried that "forcing" would cause stuttering or other problems as I though she was left handed, so I just said "Whatever feels best for you".

So she copied me, but "mirror image" and generally she eats the opposite way round to most people. People sort of "half notice" but do not understand till told as to what is different!!

Over the last few years I have trained myself to do many things with my left hand as it is sometimes easier to do something with the other hand. It has proved beneficial.

Marking as off topic as it is.

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#29
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/12/2012 4:08 AM

i mean we used the probleming one in the place of a good one....

we have 3 motors running of same capacity everything (pump,same crude,same motor capacity)...

so the load is not a problem....

motor is the problem....

my friend said that it could be some winding mistake (in lap/wave winding)....

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#31
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/12/2012 7:17 AM

Are they running in parallel and outputting into the same pipe?

Have you tried running the "bad" pump on its own?

Did it run ok?

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#34
In reply to #31

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/13/2012 11:21 PM

ya we tried.....and it didnt and wont be different...

i am sure the problem is not from the load side..its in the motor...

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#35
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/14/2012 11:11 AM

You could still have a partial blockage in the output of the problem pump, especially if there is an isolating valve......the valve itself may be out of adjustment, the foot(?) is loose maybe.......visual proof is needed that everything is OK.....

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#37
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/14/2012 12:18 PM

Hi Andy; are 'shipping of crude' pumps positive displacement?

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#38
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/15/2012 12:46 PM

No idea....

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#40
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/15/2012 2:15 PM

Oh - I thought you must as you keep on about a blockage - which would have the opposite effect in a centrifugal pump situation.

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#41
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/15/2012 3:12 PM

Opposite effect to what? We have not had an answer back that the pipe/valve has been checked yet.

If the outlet is blocked, the load will usually be higher.....

If the inlet is blocked, the load will be less in most cases that I am aware of......

Have we been informed what type of pump it is? If yes, I seem to have forgotten.....

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#44
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/16/2012 10:17 AM

All the crude oil pumps I have ever dealt with were centrifugals. The S.G., TDH and viscosity never required a positive displacement pump and the capacities were always large enough that P.D.'s would not have been economically attractive. Often a little bit of preheating to the crude makes it quite suitable for centrifugal applications.

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#45
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/16/2012 5:50 PM

Thanks and me too but I began wondering if Andy G had come across 'nodding donkeys' or similar used for transfer, as his continued insistence on a blockage problem makes no sense at all in a mass flow hp performance context.

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#46
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Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 6:04 AM

Even a centrifugal pump experiences extra load when the output is stopped/slowed (let us ignore the possible over heating effect for some liquids which may prove eventually dangerous).......which is simply why I was hoping that the OP would check that everything was in order at some point)

Why are you making such a "song and dance" about this???

It comes over to me as an unnatural animosity on your part, not a personal trait that I myself have any respect for at all.......I am sure I am not alone.

Try calming your aggressiveness down a little please. I am always fully prepared to learn something new from someone who knows better, but not in the manner you use.....(up to now you have not really made a proper attempt to "educate" me or anyone else with pertinent infos, why is that?)

Most but probably not all vacuum cleaners are basically centrifugal (air) pumps (centrifugal fans). Blocking the outlet slows the motor down as the pressure rises......that is an easy example that most have either experienced in their lives, or can test it themselves easily....its not a myth that blocking the output causes extra load.......

(Of course blocking the inlet tends to unload the motor and therefore the motor speeds up, sometimes considerably and as some may have found to their cost with home built CNC machines (using a vacuum cleaner), it will eventually overheat due to reduced cooling air flow......in a liquid centrifugal pump, this may possibly also happen once the maximum vacuum has been drawn, if that does not allow all the liquid to exit fully......this depends heavily on design and efficiency of course - but not needed in this discussion really.)

Have a really good day anyway, everyone here.

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#47
In reply to #46

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 10:41 AM

I got tired of waiting for real information on this thread, so I finally did consult my Ouija board for some answers. Here's what I found out:

Management got tired of waiting for prabut29 to solve the pump problem after four days of downtime without even a plausible diagnosis. Management paid for a service team from Siemens to examine the installation. The team consisted of just one engineer with three current transformers, a tachometer, three high voltage oscilloscope probes and a four channel oscilloscope. The first thing the engineer did was examine the operating speed of one of the working pump motors. The engineer quickly found that the rotational speed of the working motor was half that of the new motor's data sheet. The new motor was trying to do four times as much work as its rating. This explained the higher current draw of 300A instead of 75A. The thermal overload protection was preventing the motor from destruction. The engineer arranged for a gratis swap out of the wrong new motor with a correct new motor. The correct motor was delivered in just three days. Troubleshooting time took only two hours with the correct equipment and a knowledgeable person to analyze.

prabut29 is now refining his resume.

This fantasy is just an honest reporting of what my Ouija board told me.

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#49
In reply to #47

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 11:04 AM

LOL!!!

and possibly fully correct!!!

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#51
In reply to #49

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 11:31 AM

Thanks

By the way, did anybody notice that for a three phase motor to produce 500 horsepower with only 75 amperes of current per phase at an ideal phase angle requires some considerable voltage.

500HP≈373kW

373,000W/(3*75A)≈1,660V

Unqualified people should not be trying to troubleshoot a cathode ray tube TV that has these voltages. This high of a voltage and hundreds of amperes of current available is not a safe place for an unsupervised novice.

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#63
In reply to #51

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/18/2012 3:51 AM

i couldnt able to get what u trying to explain here.

better read it completely.

the other motors took 75Amps for that load.

so we expect approximately same current when we use the new in that place.

and its 3.3KV supply.

its SHOULD BE the problem in the motor internal things.

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#65
In reply to #63

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/18/2012 7:10 AM

This calculation is a basic calculation of power. I performed this in an attempt to fill in some of the information that you did not provide us until now. It is not an accurate calculation because I had to assume additional information that you still have not provided. The fact that you do not recognize this basic equation and that you do not provide us additional information when we ask for some is why this thread has reached an impasse.

I enjoy helping people solve their engineering problems. I cannot help a person that does not understand my questions.

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#67
In reply to #65

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/18/2012 10:23 AM

GA

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#64
In reply to #51

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/18/2012 3:57 AM

we are dealing with 5000HP motors in out plant.

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#53
In reply to #47

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 11:43 AM

what is that ouija board?

i am new to this forum.just found lot of good discussions and posted my issue.

i really couldnt able to get what you trying to say.

i hav posted a comment of the problem.

let me know if you need any other details.

and thanks for the answers/explanations.

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#54
In reply to #53

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 12:17 PM

I posted a Wikipedia link to a Ouija board earlier and again just now. In this case I'm just humorously saying that I'm making up information to try and explain your motor failure.

The information I'm making up are some plausible reasons why your new motor is not identical to your old motor. (Don't say that they are because the new one doesn't work.) Since my parody got your attention, here's what I want to know.

First, what is the running speed (RPM) of your old motor shaft and your new motor shaft? Another way to answer this is how many poles do each motor have?

Second, what voltage and currents are running through the old and new motor windings when not connected to the pump load and when free running. The voltage and frequency of the AC across each winding should be specified and the magnitude and phase of the current should be specified. This will allow us to say how much real power each of your motors is drawing and is capable of providing to the rotor.

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#55
In reply to #53

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 12:19 PM

When the pump stopped, did the overload device operate or did the motor just sit there, hum and make smoke?

Come on. Answer the friggin' question!

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#58
In reply to #53

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 1:52 PM

prabut29,

You still have not addressed the issue I raised, and am still convinced is the nature of your problem. I still believe you will find that your motor connection is not correct for the applied voltage. As I suggested, it could easliy be that you are connecting in Star because that is what you usually connect to for 400/230V motors, but this may be a 690/400V motor, in which case connecting in Star would give you almost no torque under load but would appear normal if there is no load connected. This is exactly the symptom you are describing.

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#48
In reply to #46

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 10:54 AM

Actually with a centrifugal pump when the discharge is blocked or the valve closed, as during start-up, the flow is reduced and the pump climbs back up on its curve with higher TDH and the BHP/KW requirement is reduced considerably.

A good presentation is at http://www.gouldspumps.com/cpf_0009.html.

I doubt very much that they would be using either a Radial Flow Pump or a Mixed Flow pump for a Crude Pump application where the BHP/KW would rise to Shut-Off/Blocked Flow conditions. You are correct that operating for too long a period at Shut-Off means that all that BHP/KW draw is going into heating up the fluid. I wouldn't be as worried with crude as I would with a lighter hydrocarbon like kerosene, naphtha or gasoline etc. since it has a much higher flash point.

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#50
In reply to #48

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 11:05 AM

Many thanks and very interestingly put....

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#60
In reply to #46

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 5:31 PM

"It comes over to me as an unnatural animosity on your part, not a personal trait that I myself have any respect for at all.......I am sure I am not alone".

If being wrong so upsets you - try getting it right

I look forward to the "always happy to admit I'm wrong", "I am sure I am not alone" in waiting for.

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#66
In reply to #60

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/18/2012 10:20 AM

Big error, I am not upset (I never get upset by complete morons on a blog, its simply not worth getting upset over any blog entry, surely you agree?).

I was just trying to improve your manners....

Probably a lost cause......I have now given up on you completely.....you may go your own way on anything....

Your problem not mine.

I learnt what I needed to know from another here with far better knowledge, good manners and a friendly word or two!!!

Note. It can be done!!!

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#68
In reply to #66

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/19/2012 2:01 AM

Ok, we can go the "personal" route if you insist

Factually, you learned what you need to know because I knew you were wrong. Now if a "complete moron" can see it, where does that put you?

It's your "absence of manners" in jumping into threads you know zero about and holding forth repeatedly with oppressive "authorotay", that ruins dialogue between serious and knowledgeable members, which needs the attention.

However, what I note "can be done" is this process of me pointing it out, you do the tantrum, and then you "learn from it others". At least you learn.

Of course it means they, and many others, now realize you are "full of noise", but yep, the methodology seems to be your choice and seems to extrude tiny factoids through the egocentric rinohide.

I.e. I don't see the "I am wrong" you are very fond of spouting, even to the 'others' who have 'learnt you' what you had wrong.

You may have ground down numerous others on numerous topics until they just can't cope with the relentless noise - but as you observe I care nothing for 'popularity' - just the facts - so for you and your personal-fall-back-when-wrong - I'm not such easy meat.

Do continue

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#69
In reply to #68

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/19/2012 8:06 AM

Blah Blah Blah.

....and still not nice in any way.......give up and go home.

I certainly will not be bothering to read any more of your posts!!!

So a very positive aspect for me!!!!!

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#70
In reply to #69

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/19/2012 6:36 PM

Um-mm - the only thing in that post resembling a 'fact' is Red Fred's Sig line, which apparently you are too ill-mannered, or too obtuse to realize you have pirated, or too bloody minded to admit it, because of, or despite, forum wide hints for weeks.

Yes, I'm sure many would agree your 'reading' the posts of others is indeed very selective.

But now I have 'learned you' something new - I'm fascinated to see if you;

1. argue some pathetic excuse

2. refuse to change

3. admit your were too thick to comprehend Fred's comment at the time.

4. change it and pretend you never bungled / it never happened

5. change it and apologize to Red for your mistake

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#36
In reply to #34

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/14/2012 12:16 PM

So what have you measured? To say that it has to be the motor, implies to me that something was measured. What did you measure and what was the result? Did you think that we can devine what and where your motor is failing by consulting our ouija boards?

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#32
In reply to #29

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/12/2012 10:11 AM

Has anyone megged out the windings and checked for a short?

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#33
In reply to #32

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/12/2012 10:24 AM

I certainly haven't.

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#39

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/15/2012 1:15 PM

I still think it is misconnected. The symptoms still all fit. Runs NORMALLY when decoupled, stalls when a load is applied. A partial blockage however is a good point IF it is in fact a Positive Displacement pump. If not, then the lack of flow would mean LESS load on the pump and would not cause a stall.

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#42

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/15/2012 3:20 PM

It seems the OP has bailed out, leaving the rest of us guessing.

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#43
In reply to #42

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/15/2012 3:34 PM

Then he has probably found his problem and not had the decency to tell us what it was.........typical!!

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#52

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 11:40 AM

not sure how many got the issues.may b something wrong in my english.

let me make it elaborate:

we are using 3 shipping pump of 500HP each.

we have not used one pump for a long time (may b a year)

winding resistance and insulation resistance where checked and its same for all the 3 motors (new and the 2 old-exixting)

so we installed a new 500HP seimens motor in that place and when we done no load test. results are good with proper current,wdg temperature.

then we coupled with the pump and hav run the motor. it got tripped with high current (300Amps)

we are using MP-3000 relay for protection.

after repeated runs we got same result.

so we replaced this new motor in the place of existing motors (as we thought it might b pump/load problem in that bed)-we used the breaker of that old motor-everything kept constant except motor was replaced with the new one.

but still same results.it got tripped.

again when we do no load test.its working fine.it runs for hours without any issues.

so its the problem is not from the load side.

now we are sending to the vendor to check the internal coil.

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#56
In reply to #52

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 12:23 PM

Ok. What is the mechanical load? Is the motor appropriately sized to drive it? If it is connected to a pump, what is the operating flowrate and pressure rise through the pump?

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#57
In reply to #52

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 12:24 PM

Did you check all of the jumpers and connections inside the motor's make-up box to ensure that they match the original motor exactly? Do the legend plates on the motors match exactly?

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#59
In reply to #52

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 3:42 PM

To say:-

again when we do no load test.its working fine.it runs for hours without any issues.

so its the problem is not from the load side.

....is to my mind simply incorrect. Although a no load run test is a good idea, it says NOTHING about the loaded situation, which is plainly the problem......

So your statement has to be wrong as written.

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#61
In reply to #52

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/17/2012 11:00 PM

Give complete nameplate details of the motor. Also obtain from manufacturer the no/full load PF and no load current. Check all three phase voltages before starting and during running/tripping. Record tripping current in all 3 phases. Give full details of starter and trip current setting. Check speed of motor matching to the rated speed of pump.

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#62

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/18/2012 3:43 AM

is that, i am not still clear about my situation?

we interchanged the motors with the near by one (the one which was running fine till now) and when have run with the new motor we got same problem with the new one [tripped with high current].

again when we use the old pump in that place it runs fine.

so there is no way the load details comes to picture.

what more details we need here.

the old and the new are the same/exact same type motors.

the problem should be only from the motor side.

when we check the relay it shows at the time of trip its 300 Amps.

its 3.3KV motor and peoples making calculations without knowing the voltage details.

@redfred: what is that prabut29 is refining resume does means?

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#71

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/19/2012 7:08 PM

With the same kind of moribund curiosity I would exhibit watching a train wreck taking place in slow motion, I trudge on; i cannot let this go!

Here's a good one, it would hilarious it it turned out to be the problem!

What if it's not the motor or the load at all, what if it's the MP3000?! (For those unfamiliar, an MP300 is a Motor Protection Relay made by Solcon.) What if, by chance, Someone forgot to program in the correct CT ratio into the relay, or when the motor was changed, so were the CTs and they used a different ratio? So it isn't really pulling 300A under load, the relay just THINKS it is and is acting on that erroneous information. Worth thinking about and easy to check. God knows I've done it! Left the CT ratio at the factory default value on a Multilin 469 once, that was fun.

The part of this ever evolving yet incomplete story that fits is, if I interpret it correctly, that a DIFFERENT motor was installed in the same place and did the same thing!

The part that doesn't make sense is that the No Load current was supposedly normal. Or was it?

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#72
In reply to #71

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/19/2012 7:59 PM

An uncalibrated motor protection certainly could be the problem. It could be almost anything. Frankly with the sparse information from the OP and the even thiner level of comprehension, I believe what we have here is an ESO problem.

Equipment Superior to Operator

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#73
In reply to #72

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/19/2012 8:53 PM

ESO=??

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#74
In reply to #73

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 12:04 PM

Read it again with your glasses or lenses in!!!

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#76
In reply to #74

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 5:20 PM

Read the posting time difference with your brain engaged Mr Obnoxious

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#77
In reply to #76

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 5:36 PM

DS,

read the ORIGINAL POST fully through before you make such stupid ignorant posts again!!

The original post was:-

An uncalibrated motor protection certainly could be the problem. It could be almost anything. Frankly with the sparse information from the OP and the even thiner level of comprehension, I believe what we have here is an ESO problem.

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Get it now slowcoach?

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#78
In reply to #77

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 6:05 PM

Anonymous Coward is it now Andy?

And you still haven't considered it was clarified in edit time?

I am again amazed at how tiny tunnel your thinking is.

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#79
In reply to #76

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 7:32 PM

Actually your brain and his were BOTH not engaged.

Simple mistake. Anyone could make it!!

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#80
In reply to #79

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 11:38 PM

Got it now.

I could have sworn that the acronym definition wasn't there.... then again I swear a lot for dumber reasons than that.

What are those yellow circles with the dark smudges supposed to be?

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#81
In reply to #80

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/21/2012 10:36 AM

LOL!! Well said!!!

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#75
In reply to #72

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/20/2012 1:34 PM

ESO, that's fantastic! Never heard that before, I have to remember it for future use, comes up a lot.

Thanks!

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#82
In reply to #71

Re: 500 HP Motor Good With NO Load, But Stops at Load

01/21/2012 1:02 PM

we just interchanged only the motor which was already running fine.

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