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Electric Motors/Fan motor usage

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Question
If I build a big fan with 5ft blades, what type of motor would I use?...a motor that can turn a heavy load with high torque

Answer
WOW  five foot blades,?  hell of a ceiling fan.

As you described blades,  then this is likely a centrifugal fan not a blower,    and a fan is not a blower,  a blower is not a fan.

Certain restrictions and other considerations are critical,   such as blade pitch, rpm, type and weight, safety covers,   considerations on what could be sucked into the spinning blades,   

Torque is turning HP,    yes there are different DESIGN motors,    same HP, same everything   say a 25HP motor,  might be a B or standard design,    C more starting torque, D even more,  but normally something like this would have some sort of mechanical moveable restriction,  so the motor could start under pretty much no load,  then remove or adjust the mechanical restrictions,

5 foot blades,   sounds like some sort of wind generator,   that gets complicated,       

Over all the best generic options to think about      by just answering what motor for a five foot bladed fan would be some sort of three phase motor, with a variable frequency drive,   

Or a soft start where the motor is fed lower voltage on start to keep the amps down past LOCKED ROTOR,       note  a motor's highest load is at dead stop,   load or no load,   

Just the magnetizing power needed to create rotation is the max the motor will produce    

Now once it is out of locked rotor  then if the load is a long drawn out load,   then it takes time while the motor comes to speed,      

But remember adjustment of the blade pitch, the construction of and the materials compared to the SPEED,        THE NUMBER OF STARTS per hour,     most motors should really not be started more than a few times per hour,     general comment,    and it is mostly ignored

Dynamic balance,  correct alignment of the hub to the driven shaft, be it direct or belted or pulley   whatever,   all need to be straight no side pull, no pulling the motor shaft in ANY direction or plane,   

I really need to know what you are trying to do,  to help you find the right motor,   but also the right starting method,  and what options you might have,      

Just the needed pitch of the blades will make a huge difference,    and change the starting load and the running load,     

Below  motor application GUIDE for ventilation products:

http://www.greenheck.com/library/articles/33

Its a GUIDE with a lot of background info,     good place to start,  and if you want to disclose what you are attempting in detail  I am happy to get into the details and options you can consider,      a fan often needs nothing more than a standard off the shelf motor,   but it depends on the application, and all the considerations meentioned above,    let me know if I can help with the details,  

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Expertise

Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site

Experience

30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.

Organizations
EASA, IBEW [retired], other specialty organizations, Lubrication, Vibration EDI, Tribo-electric Councils

Publications
Currently fielding concerns at this site under "Home Electrical"

Education/Credentials
4 year technical, College level specific courses, EASA repair courses, vibration analysis electronic and electrical trade school.

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