Motor Sizing
Motor Sizing
(OP)
Can someone help on how to select and size ac electric motors? Assuming you want to select a squirrel cage induction motor, how do you go about getting the actual size. You may assume any mechanical load, please.





RE: Motor Sizing
Once you have calculated the load there are other factors like enviroment(heat), speed range required, response required(inertia matching), number of starts per hour, if you need to produce torque at low or high speed, the type/condition of the voltage you have available and the type of drive or starter you use.
But if you ignore all the above and have put a torque wrench on a wheel of your cart and have measured 40 in-lb of torque to move the cart and you know the wheel needs to spin 1200 rpm the equation would be.
Torque(in-lb) x RPM
------------------- = HP
63,025
40 x 1200
--------------- = .76 HP
63,025
Most likely the motor would have a very hard time starting in the above example and would trip the overload relay.
Hope this helps.
Barry1961
RE: Motor Sizing
Define the load operating speed in rpm and get the torque required (Lb*Ft).
BHP= rpm*Lb*Ft/5252 (break horse power)
Assume a service factor around 1.10
Motor required HP= 1.1*BHP
After a motor HP is defined, the speed-torque curve of the motor is required as well as the reflected inertia of the load to the motor shaft (WK^2). Whit that information the starting analysis is done to ensure satisfactory motor life and performance.
Most motor manufacturers will provide support to potential customers.
RE: Motor Sizing
http://www.patchn.com/motorformula.htm
RE: Motor Sizing
RE: Motor Sizing
the motor will be used. This identifys the Design of the motor, which will be used. This is an addition to what has all ready been said.
RE: Motor Sizing