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New motor for new load ?

New motor for new load ?

New motor for new load ?

(OP)
hello,
   i have a quistion,i want to select a motor for a new load i don't know its power.
How can i calculate the load power to select the motor?
in another meaning i want to calculate the mechanical power of the load and then convert it to electrical.
thanks every one

RE: New motor for new load ?

The first things you need to know is what the characteristics of the load is. Is it high inertia, linear, difficult to start because of sticking load or bearings and many such things. Then decide what speed range you need or if you will run constant speed DOL. Next thing is what torque does it need when running, how torque depends on speed. Will it run 24/7 or just a few minutes now and then or anything in between. Will it plug brake? Environment? Dirty, hot, wet? Lots and lots of things to consider.

The more of these questions you can answer the better your choice will be.

The conversion from mechanical power to motor rating is the least problem. We do that when you have given us more facts about the application.

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

RE: New motor for new load ?

(OP)
thank you my friend,
i will tell you some data,
i have a manual sliding gate and i want to make it to opend with a motor.
the gate mass=600 kg
the suitable speed=30 rpm
i thought about gear motor.
now how can i determine its power to select?

RE: New motor for new load ?

It would be better to know the linear speed of the gate. I assume something like 1 m/second and acceleration to that speed in one second. It also helps to know what force is needed to move the gate. I assume (again) that the gate cam be opened manually and that you do not need to apply superhuman forces. So, something like 300 N seems plausible.

The force needed to accelerate the gate is then 600*1=600 N [kg,m/s^2] and the power needed to move it is 300*1 W [N,m/s]

Assuming again that gear and motor are 50 % efficient, you will need around 600 W input to the motor. That is just below 1 HP. I would select a 1 HP motor.

Now, can such a motor apply sufficient torque to accelerate the gate in 1 second? There are motors with a starting torque that is around 3 times the rated torque. The efficiency is a little lower for those motors (high slip) but efficiency doesn't count if the gate doesn't open/close continuously - which is seldom the case.

Combining static (300 N) and acceleration force (600 N) gives you a total force equal to 900 N to accelerate the gate. That is clearly within reach with a 1 HP motor.

One problem that you may have to think about is how to stop the gate. I would use a motor with integral brake - especially if you need to stop quickly when a 'squeeze bar' on the gate contacts animals, humans or vehicles.

The gear ratio is something you need to calculate yourself. You will probably have a motor speed between 1400 and 1470 RPM if 50 Hz and 20 % higher if 60 Hz.


 

Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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