ID Fan efficiency questions. 1

[Andy]

I am interested in the practicality of monitoring the efficiency of a large (~1.5MW) ID fan by looking at the ratio of electrical power in to hydraulic power out.<br>
<br>
I guess I have two questions - can I assume a fairly fixed power factor in a motor of this size (it's not measured and it's been a *long* time since university!), or will it vary if the motor speed stays the same ?<br>
<br>
.. and can anyone point me towards a formula for the hydraulic power supplied by a fan ?<br>
<br>
thanks,<br>
<br>
andy

 

[man99]

I wish I had the formula right here with me but i don't. I suggest you refer to the Vickers hydraulic manual. If you can wait till next week I will find the formula and send it to you.I did some work on fluid power while in school.

 

[man99]

I was able to find the formula to help you with, the formula is HP=(Tn)/(63k or 63,000) <br>
<br>
where T = Torque <br>
n = rotational speed (rpm)<br>
HP = horsepower<br>
As the motor rotates, a load resistance and sometimes friction is overcome, so work is done and power is transmitted. Also, you may want to find the efficiency of the pump if you desire to and here is a formula to find that<br>
n(m) = ((theoretical power required to operate pump)/(actual power delivered to pump))*100<br>
or<br>
n(m) = ((pump output power assuming no leakeage)/(input power delivered to pump))*100<br>
<br>
Use these aforestated equations to find mechanical efficiency which tell you the amount of energy losses due to reasons other than leakage. <br>

 

[JoeA]

Regarding the power factor of the motor. Assuming it an AC Induction Motor, then it definitely is not a constant or almost constant. It is very low at low loads and improves as the load on the motor increases. For this reason, it is usually best to size a motor close to the full load requirements of the application. Most motor manufacturers can provide the relationship between load and PF.<br>
<br>
Best Regards....Joe Agro<br>
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