Determining Efficiency, P.F., L.F. of loads

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excited_electrone

excited_electrone

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Electrical E.I.T
Hello all,


Before posting my question, I request your pardon if you find anything useless/foolish content as I have just started my practice as an EIT in Ontario.

So, my question is for the project that I am working on for creating a load list for one of our clients. Referring to old documents of company, I found some excel sheets for the load calculation for similar project. In here, the calculation is based on the information given in Read Me sheet, where I find the values of efficiency, p.f., l.f.(load factors) predetermined based on the power rating only of motors, VFDs, Power Loads such as X'mer.

Without having nameplate of any load(let's say motor) how is possible to determine such values? Is there any standard/code to determine them just from power ratings?

Ex. Efficiency for loads,
Power(HP) Eff
0-4 0.79
5-9 0.84
10-19 0.86
20-49 0.89
50-99 0.9
>100 0.92
VFDs 0.95
Others 0.85

Seeking Help from Experienced!

Thank you.
 
Shockerzz said:
Without having nameplate of any load(let's say motor) how is possible to determine such values?
Click to expand...
Shockerzz: The answer is you can't.
It is of utmost importance for the crew in the field to get accurate nameplate information.
Before I get a call from the field about a piece of unknown or new unfamiliar equipment, they will text me a photo of the nameplate becasue they know that is the first thing I ask for.
Cheers
 
Shockerzz said:
Hello all,


Before posting my question, I request your pardon if you find anything useless/foolish content as I have just started my practice as an EIT in Ontario.

So, my question is for the project that I am working on for creating a load list for one of our clients. Referring to old documents of company, I found some excel sheets for the load calculation for similar project. In here, the calculation is based on the information given in Read Me sheet, where I find the values of efficiency, p.f., l.f.(load factors) predetermined based on the power rating only of motors, VFDs, Power Loads such as X'mer.

Without having nameplate of any load(let's say motor) how is possible to determine such values? Is there any standard/code to determine them just from power ratings?

Ex. Efficiency for loads,
Power(HP) Eff
0-4 0.79
5-9 0.84
10-19 0.86
20-49 0.89
50-99 0.9
>100 0.92
VFDs 0.95
Others 0.85

Seeking Help from Experienced!

Thank you.
Click to expand...

Congrats on your EIT. What is the reason for determining the efficiency, pf, l.f., etc?
 
When in the beginning stages of a project, motor load data is preliminary. Default values have been established for the motor loads based on the HP / KW motor size. These value include PF, EFF and LF.
Do you know what motor LF is ? I would be surprised if you do. Contact me for clarification.
 
JEFF MILLAR said:
When in the beginning stages of a project, motor load data is preliminary. Default values have been established for the motor loads based on the HP / KW motor size. These value include PF, EFF and LF.
Do you know what motor LF is ? I would be surprised if you do. Contact me for clarification.
Click to expand...
It is load factor if I am not wrong! Power used divided by its peak demand! {Or is it a calculation based on code/standards, (calculated load-10000)*0.5+10000, isn't it load demand factor?}

About the default values, is it established by my company or it's something generalized for everyone? (I mean if it's only determined based on HP/kW then it must be generalized, is what I think!) And if that's the case would you please elaborate more about how to find it/where to find it?

Thank you in advance!
 
Last edited:
Some low tech equipment can often provide high tech answers. Comparing a motor's actual RPM to it's synchronous RPM and it's rated full load RPM can tell you a lot. In other words, measure the motor's "slip".
 
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