Jump to content
Mechanical Engineering
  • 0
mehlam hamid

Determine Motor power

Question

I need to select a vertical motor which drives a vertical Rotor weighing approximately 1000 kgs & 6 m in length.

I know the basic power equation P(power)=T(torque) x ω(Angular velocity)

But how to find the torque??  - Given-  RPM(revs. per min) & M(mass) 

Also, I do know that T=I(moment of inertia) x  α(angular acceleration)

But, again how to know Inertia and Acceleration before even manufacturing the rotor??!! 

the rotor looks somthing like this: https://www.process-worldwide.com/gig-karasek-gmbh/photos-videos/company/235606/500966/#1

 

PS - Im an intern at a company that manufactures ATFEs(agitated thin fill evaporator), reactors ,ATFDs(agitated thin film dryer)....etc for chemical processes

Share this post


Link to post
Share on other sites

4 answers to this question

Recommended Posts

  • 1

Well, are you trying to accelerate this rotor, or are you concerned only with steady running? You have to define the problem before it can be answered.

As  for the mass moment of inertia, you can't calculate such until you have a proposed design. After you define a design, you can calculate the MMOI and see if the system performance is satisfactory or  not. On the first try, it often is not, so you propose a better design and try again. This is why design is described as an iterative process.

DrD

Share this post


Link to post
Share on other sites



  • 0

Thankyou DrD for replying,

well let me describe you the procedure i)The process department defines the tip velocity & OD of the rotor required to  process a substance.

ii)So, Well get the required RPM of the rotor (v=rω) ,and we need the rotor to run steadily at this rpm

iii)Rotor Design is Confirmed, and say I find a rough MMOI 

.......................................................................................................................

Now, How do I find the Power Required to run the rotor steadily at say 1400 RPM??

And I do know that a high initial torque is required to get the rotor from 0 to 1400 RPM, How to find this initial Torque??

I did try using T=I(moment of inertia) x  α(angular acceleration)

I know the MMOI , and α = dω / t where dω will be 2*pi*(1400-0)/60

Now here's the problem HOW ON EARTH WILL I BE ABLE TO GET THE TIME 't' ??!

Share this post


Link to post
Share on other sites
  • 0

If you are looking for steady operating power, the SumTorq = I * alpha does not help. In steady operation, all of the power input must be converted to heat. Where is it going? What are the torques that act on the system in steady state? Perhaps some viscous drag? Is there a brake? Is there a friction rub? Find these and figure out how much power they consume at operating speed. That is the required input power.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.







×
×
  • Create New...