Message Board Thread - "formula for energy loss"

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formula for energy loss scott waterman 12/8/2004
is there simple formula for calculating the cost of a over heated bearing, motor or anything causing resistance?
thanks
scott from line locators inc.
 
Re:formula for energy loss gwebb 12/8/2004
Where I work we figure by lowering the amps by 1 = $200 a year
 
Re:formula for energy loss electricpete 12/8/2004
I believe in general the energy cost of hot bearing or hot electrical connection is small. The motivator for repair would normally be cost of failure: possible disruption of process, increased damage/repair cost as compared to preventive, possible personnel injury etc.

It was mentioned above, motor power would be one good way to attack the problem if you want to and if you have two comparison motors under identical conditions except for the fault. Best estimate of power includes measurement of voltage and power factor along with current.

It is also possibly you can generate a s.w.a.g. of the energy produced using heat transfer calculations, and the temperature profile, again with a known reference to compare it to.

For a hot connection, you can measure on-line millivolt drop or off-line resistance to estimate power consumption.

In general, it would not be worth the time to do the calcs in my opinion because these losses are generally small, but I may be wrong.
 
A great question, and one I've been asking for a long time Scott Willits 12/9/2004
I recently got my hands on a loaner PowerSight 3000 energy analyzer, which has four voltage probes and four current transducers so you can monitor the entire circuit in real time and log data across various load conditions. It registers not just voltage and current, but also true power, VA power, VAR, and calculates power factor, both indepentently for each leg and combined for total power factor.

I didn't get a chance to collect enough data to discern which came first, the chicken or the egg, but I can say conclusively that for every single motor I polled data from where a significant thermal anomaly was present anywhere in the circuit, the power factor for that motor was horrible -- for several it was well under 50%.

Again, I have no way of knowing low power factor is a function of the thermal anomaly, or the other way around -- or even if they were unrelated. In most cases the overall plant system power factor was less than it could be, but it was generally always worst within the circuits where the hot spots were manifested.

While poor power factor isn't necessarily associated with increased peak power in true kW, it can affect demand charges. But most of the costs associated with it are external, in as much as it increases the current in the system and thus puts serious constraints on system capacity and puts system integrity at greater risk.

I do suspect there are direct energy efficiency costs associated with this dynamic, but I don't know enough at this point to say so definitively. My review of the literature thus far leads me to believe it's an area ripe for further investigation, and I welcome further inquiry or sources of better information.
 


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