out of ideas

[ACFIXR]

The more I re-read thru this thread the more my mind has a chance to look back in my past and see where I have seen this before. I have been working on motors for over 25 years and have never seen a free wheeling motor burn out.They have been warm but not hot enough to trip the thermal overload. The only time that I have seen motors consistently overheat and trip the thermal or burn up is when the capacitors fail and / or when there is a phase imbalance and or failure.There is more to the comment on tight bearings than you realize, wholesalers here in Tucson remove all motors from the boxes and spin the shafts to make sure that the bearings are free.It is easy to tweak a motors bearings by dropping them and or bumping them. All motors that have overheated that I have seen usually have the signs of grease melting and running out of the felts or caps and running down the edges of the mounts.
Lately I have seen a large amount of capacitor failures. I have heard from a very good souce that high voltages can cause cap failures. Your situation has all the signs of a cap causing your problem. High amps/overheating. Could possibly be from being miswired and or high voltage.

[Airmechanical]

here is what was said;


THE OP stated this;

new motor runs the same, 12.6 amps without belt

then, chris stated about how he should check blower curve

then i told chris, the unloaded NEW motor will draw no where near FLA

therefore (chris's) blower curve theory can wait till the motor problem is solved

then we seen the next post;

So your saying an oversized/undersized/caveatting blower motor will not run hot/over amped? I find this hard to believe

so we ALL assumed you new the motor was not hot, therefore no reason to be drawing anywhere near FLA

so were both on the same page right

do you still think there is not a blower motor problem?



.

[timebuilder]

There is more to the comment on tight bearings than you realize, wholesalers here in Tucson remove all motors from the boxes and spin the shafts to make sure that the bearings are free.It is easy to tweak a motors bearings by dropping them and or bumping them.

We have started spinning the shafts whenever we pick up a motor. I had one at Grainger just last week. I asked the guy if I could open the box and see if the shaft spins. He gave me a funny look and said "sure."

I opened the box and sure enough, it would not budge. I said "here, you try it." He went and got another, and that one worked just fine.

It is amazing to me how often this happens today.

[tipsrfine]

Ditto on the motor shafts not turning or very hard to turn fresh out the box.

[kdocsr05]

Attached is a spreadsheet to calculate amps vs load. You input the power factor at full load and the amps at full load. It has some assumptions listed (neglect leakage reactance and losses). Under the assumptions the real component of current varies directly proportional to the load and the reactive component of current is constant. The total current is of course square root of sum squares of real and reactive components. If that sounds complicated, remember all you have to do is fill in those green cells labeled FLA and PF (PF corresponding to full load conditions). If there is an efficiency listed on the nameplate, then nameplate data can be used to estimate power factor. If know the horsepower and speed, we can estimate power factor.

In addition, if your voltage deviates from nameplate voltage you would need to correct for that.

Try working the number for the OP’S motor and see what you find. By lowering, the pf to .3 this motor draws close to full load amperage unloaded, and the same amperage loaded.

The answer to this condition now becomes apparent the building has conditions affecting power factor.

In a purely resistive AC circuit, voltage and current waveforms are in step (or in phase), changing polarity at the same instant in each cycle. Where reactive loads are present, such as with capacitors and inductors energy storage in the loads result in a time difference between the current and voltage waveforms. During each cycle of the AC voltage, extra energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric or magnetic, and then returned to the power grid a fraction of a second later in the cycle. The "ebb and flow" of this nonproductive power increases the current in the line. Thus, a circuit with a low power factor will use higher currents to transfer a given quantity of real power than a circuit with a high power factor. A linear load does not change the shape of the waveform of the current, but may change the relative timing (phase) between voltage and current.

You may need the local power company to resolve this one.

Trying to get the file formated to attach please stadnby. I'm not able to upload this spreadsheet i will e-mail to all that request,

[tipsrfine]

In response to plainjs, thanks for your input. You are not the first nor only one with these suspicions. Unfortunately, I can't get back to test these theories just yet. I added in the original post that I had shed lighting, which was very vague. In fact, what I had done was shut down approx. half of the total lighting at a control point in the master suite. I did not disconnect power to the lighting panels as you suggest, and I did not measure for DC voltage as above quote recommends.

I have yet to bench test the motors(lots of opinions on this), which I believe will be informative as to whether I am dealing with motor or power supply issues.

whatever the outcome, I'll gladly join you at the bar. how long is the ride from Buffalo?

http://www.saunderselectric.com/PDFs...-harmonics.pdf

I'm officially casting my ballot for non-sinusoidal load of the new lighting system causing the op's motor problem. The following link is just one of the articles I have read that leads me to this conclussion. Comming from 4 years of experience this may be just a guess and I may very well be mis-understanding what I've been reading.

[timebuilder]

http://www.saunderselectric.com/PDFs...-harmonics.pdf

I'm officially casting my ballot for non-sinusoidal load of the new lighting system causing the op's motor problem. The following link is just one of the articles I have read that leads me to this conclussion. Comming from 4 years of experience this may be just a guess and I may very well be mis-understanding what I've been reading.

From what I read there, you need loads that interrupt the normal sine wave loading to generate the harmonics. A gate-controlled device like an SCR (silicon controlled rectifier) or its AC cousin, the TRIAC are given as examples of the devices that only flow current during a portion of the sine wave cycle.

Unless these types of devices are in use, they are not the cause of the problem.

I'm leaning more toward the idea that a large number of fluorescent ballasts are putting a lot of inductive reactance on the system, which could be corrected with power capacitors to change power factor to a more acceptable value.

[tipsrfine]

From what I read there, you need loads that interrupt the normal sine wave loading to generate the harmonics. A gate-controlled device like an SCR (silicon controlled rectifier) or its AC cousin, the TRIAC are given as examples of the devices that only flow current during a portion of the sine wave cycle.

Unless these types of devices are in use, they are not the cause of the problem.

I'm leaning more toward the idea that a large number of fluorescent ballasts are putting a lot of inductive reactance on the system, which could be corrected with power capacitors to change power factor to a more acceptable value.

I read that light balast produce non-sinusiodal draws on the supply. No that's wrong, I was thinking about dimmer switches. Maybe that fancy new lighting is converting ac to dc? Maybe this home shares a transformer with someone else that is drawing a large non-sinusoidal load?

[tipsrfine]

I'm leaning more toward the idea that a large number of fluorescent ballasts are putting a lot of inductive reactance on the system, which could be corrected with power capacitors to change power factor to a more acceptable value.
Removed link

The op says the new lighting is all "low voltage" lighting. I don't know what that means, but I'm thinking its not the usual fluorescent with the ballasts. Maybe "low voltage" means also that their converting ac into low voltage dc which means rectifiers which means non-sinusoidal load. Plus, I just like saying non-sinusoidal.

[ChuckHVAC]

The op says the new lighting is all "low voltage" lighting. I don't know what that means, but I'm thinking its not the usual fluorescent with the ballasts. Maybe "low voltage" means also that their converting ac into low voltage dc which means rectifiers which means non-sinusoidal load. Plus, I just like saying non-sinusoidal.

Good stuff Tips, but it doesn't exactly apply here. The relevence of your information is for shared neutrals on 120v loads. Shouldn't apply to 240v loads. If the motors, wiring and test equipment are ok, then I'm sticking with power factor for now.

[Airmechanical]

well was this job figured out yet



.

[timebuilder]

The op says the new lighting is all "low voltage" lighting. I don't know what that means, but I'm thinking its not the usual fluorescent with the ballasts. Maybe "low voltage" means also that their converting ac into low voltage dc which means rectifiers which means non-sinusoidal load. Plus, I just like saying non-sinusoidal.

Low voltage lighting generally uses a transformer and then a full wave rectifier. The part exposed to the power panel is the transformer(s). A full wave rectifier would present a sinusoidal load because the entire wave ("full" wave) is being converted from AC to DC.

[tipsrfine]

Been reading a lot about harmonics, voltage harmonics, current harmonics, single phase, 3 phase etc..., havn't read anything that specifically rules it out in a 240 system. Found one article that mentioned very briefly voltage harmonic distortion in a 240v circuit. Some math about adding 10v to 240v bla bla bla.
Not saying the power factor angle is not the problem, I'm just saying I got side-tracked into harmonics & non-sinusoidal loads and I'm paying hell finding anything specific on it as it relates to a 240v induction motor. I'll keep trying & if I find anything definitive I will post it.

[ACFIXR]

Been reading a lot about harmonics, voltage harmonics, current harmonics, single phase, 3 phase etc..., havn't read anything that specifically rules it out in a 240 system. Found one article that mentioned very briefly voltage harmonic distortion in a 240v circuit. Some math about adding 10v to 240v bla bla bla.
Not saying the power factor angle is not the problem, I'm just saying I got side-tracked into harmonics & non-sinusoidal loads and I'm paying hell finding anything specific on it as it relates to a 240v induction motor. I'll keep trying & if I find anything definitive I will post it.

Have you read this yet?
http://www.aerovox.com/products/shop...t.asp?type=t10

[tipsrfine]

Have you read this yet?
http://www.aerovox.com/products/shop...t.asp?type=t10

Thanks for the link. Yeah I've read similar articles, but I guess I need a real dumbed down version to figure out if this could be a problem in a 240v motor like the op's. chuck the moderator stated it should only be a problem in 120v sharing the same neutral. Timebuilder? stated that a full wave rectifier would not be a non-sinusoidal load, but articles I've read say they are. So far my understanding is that harmonics, whether voltage or current, can affect a motor using 240v due to non-sinusoidal loads and that these loads due not have to even be in the same building-some place down the street could be causing it.
Not trying to highjack the thread, but 'til he gets back to us with more info we can entertain ourselves. I wish Chris would come back. I'm thinking he may know a lot about this & have some good links.

[DeltaT]

Thanks for the link. Yeah I've read similar articles, but I guess I need a real dumbed down version to figure out if this could be a problem in a 240v motor like the op's. chuck the moderator stated it should only be a problem in 120v sharing the same neutral. Timebuilder? stated that a full wave rectifier would not be a non-sinusoidal load, but articles I've read say they are. So far my understanding is that harmonics, whether voltage or current, can affect a motor using 240v due to non-sinusoidal loads and that these loads due not have to even be in the same building-some place down the street could be causing it.
Not trying to highjack the thread, but 'til he gets back to us with more info we can entertain ourselves. I wish Chris would come back. I'm thinking he may know a lot about this & have some good links.

Somewhere on Flukes site they have a good explanation of building harmonics. I went to one of their classes and the guy who taught it was great. Plus they have and HVAC instrument division so they apply their instruments directly to us.

Harmonics, to me, is simply the left over EMF from not using the entire 60 HZ signal which means the power is really not 60 HR to a degree anymore, there is left over voltage in the lines and that shows up primarily in the neutrals of commercial building, which is a very dangerous thing.

I've had first hand experience of this in the many commercial building I work in since we tend to be a large software city of the world and the building are full of computers.

That's why a true RMS meter is now the responsibiliyt of every tech in this world.

Placing bets on the info given by the poster so far as to what might be the problem, if there is one...I'm still riding in a mis-applicaiton and/or a mis-reading of the posted trouble shooting figures.

[timebuilder]

Timebuilder? stated that a full wave rectifier would not be a non-sinusoidal load, but articles I've read say they are.

I do not have an EE degree, so I am open to the idea that someone could convince me that a full wave rectifier could be considered a non-sinusoidal load. Could you give me a link to the doc you saw that suggests this is the case? Thanks!!!!

I'm always learning.

[tipsrfine]

I do not have an EE degree, so I am open to the idea that someone could convince me that a full wave rectifier could be considered a non-sinusoidal load. Could you give me a link to the doc you saw that suggests this is the case? Thanks!!!!

I'm always learning.

I'll retrace my steps, but it might take me awhile. I'm tired, got a pot roast to take out and a live-in girl friend who's feelin' frisky. Will find those articles mentioning full wave still producing non-sinusoisdal load first thing in the morning. By the way it made sense what you said about the full wave thing, but maybe it has something to do with how it goes about fully rectifying the ac current. Here is one I havn't had time to read, but I think it shows how the fully wave is actually worse than the half wave.
http://www.allaboutcircuits.com/vol_2/chpt_7/3.html

I'll find the other I did read tomorrow.

[ChuckHVAC]

I do not have an EE degree, so I am open to the idea that someone could convince me that a full wave rectifier could be considered a non-sinusoidal load. Could you give me a link to the doc you saw that suggests this is the case? Thanks!!!!

I'm always learning.

I understand the principle that a full wave rectifier would not effect the sine wave because it uses both the upper and lower part of the wave.
In actual practice the load is non-linear because it is actually switched by the diodes. Since the load is non-Linear, it alters the sine wave. Harmonics are created and the power factor can be lowered. The problem is increased when a capacitor, or other method is added on the output of the bridge rectifier (full wave) to smooth the voltage output because if you smooth the voltage you amplify the amperage variations. Here is a link which you might find interesting: http://en.wikipedia.org/wiki/Power_factor

[timebuilder]

I'll retrace my steps, but it might take me awhile. I'm tired, got a pot roast to take out and a live-in girl friend who's feelin' frisky. Will find those articles mentioning full wave still producing non-sinusoisdal load first thing in the morning. By the way it made sense what you said about the full wave thing, but maybe it has something to do with how it goes about fully rectifying the ac current. Here is one I havn't had time to read, but I think it shows how the fully wave is actually worse than the half wave.
http://www.allaboutcircuits.com/vol_2/chpt_7/3.html

I'll find the other I did read tomorrow.

While the full wave rectifier does generate second-order harmonics, I'm not sure it this is enough to be of large consequence to the op's motor. It's a shame we did not get a graphic of the effect on the waveform to see how much it may have been distorted.

This makes me wonder about the incredibly large number of motors used in RTU's in non-chiller retail environments such as older shopping malls, and the preponderance of DC power supplies being driven by the mall power grid, especially the newer generation of switching power supplies used in every computer and point of sale terminal in every store. Also, you have fluorescent lamp ballasts that all produce an inductive load on the grid, producing a change in power factor.

In other words, if the second order harmonic being generated by a full wave supply was a real power problem, I would think it would be very difficult to keep the RTUs running for very long.