Electric motor - Force / Torque 1

[killtill92]

Hello fellows,

So I am sorry for my bad English

I have a problem to understand how I can calculate the forces or torque at an electric motors stator. I need to join the stator into the housing.
So I know the torque which should react at the rotor.
I need a formula because I don't know how the torque from the rotor attacks the stator. I was thinking about 'actio reactio' but it was not possible for me to find a satisfying solution for the problem yet.
Is there some literature for this subject?

Many thanks in advance

KillTill92

 

[MintJulep]

All of it.

The connection between stator and housing transmits the full torque the motor can produce.

 

[electricpete]

I agree with MJ. I'll say it my own way...

Assuming no mechanical transmission losses and assuming steady state, there is a single torque transmitted throughout all the machine train components as follows:

Load rotor -- motor rotor -- motor stator -- foundation

There is electromagnetic torque between the rotor and stator which is equal / opposite (just imagine two adjacent magnets... the force on each is equal / opposite).

The stator doesn't roll away, so we know that it is also restrained by an equal/opposite force from the [tt][/tt]foundation/support.

Spoiler

op - Why isn't there anything in your spoiler?

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(2B)+(2B)' ?

 

[handleman]

Spoiler

Incompetence is rarely limited to a single category of endeavor

 

[IRstuff]

Spoiler

All of which the OP could have gotten from the motor specifications

That's the real spoiler

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

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[electricpete]

Yeah, the reaction torque transmitted to the foundation from the motor is an easy one (same as that load torque that is transmitted throughout the machine).

A trickier question is whether that same torque would be transmitted to support/foundation at the load machine if that load machine is something like a pump.

It was discussed (my question) here: thread404-259495

The reference I quoted and the majority of respondents in that thread seemed to think that the answer is yes, the same torque that is transmitted throughout the machine train is also transmitted to the pump to the foundation. (if common foundation, the pump and motor exert equal and opposite torques on the same foundation).

I've thought about it some more and I'm still thinking the answer is no. Draw a box around the pump and look at the torques associated with that box during steady state operation. Yes there is a torque in from the shaft and another unknown torque from the foundation (which would be equal and opposite in the absence of any other torques). But there is also fluid crossing the boundary of that box which carries angular momentum about the shaft axis. If the angular momentum of the pump discharge is different than the angular momentum of the pump sucition, then there is a torque required to cause that change in angular momentum. I say we look at the suction and discharge pipes, if they are the same direction, then maybe there is not a lot of torque associated with change in angular momentum about the shaft axis. If they are at right angles (such as an end suction overhung pump), there is a large change in angular momentum of the fluid entering and exiting the pump. The torque required to accelerate that fluid to cause the change in angular momentum must be vectorially subtracted from the shaft torque to determine the foundation reaction torque. That's just my two cents on a question that was never asked (but one that I find interesting). I might be wrong (given that other posters and references disagree it seems likely I'm wrong). If anyone wants to explain why I'm wrong feel free (it wouldn't be the first time). I realize there may also be large forces from the attached piping, but to separate out the torque effects I'm assuming the force from attached piping will be equal/opposite to the pressure-times-area force of the pipe opening at that location, which seems like it would be true if the pump is rigidly supported by its foundation and the pipe is flexibly supported from another location (in that case it is like you have a pressure vessel hanging off the pump... all forces required to contain that pressure are transferred to the pump foundation... the net force on a pressure vessel from the contained fluid is zero). There may be further forces transmitted from attached piping to the pump foundation in the real world but one design objective of the piping support is to minimize those forces.

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(2B)+(2B)' ?