On 6/16/22 20:54, John Dammeyer wrote:
OK. I realize this will be a dumb question but please bear with me especially
since I've included the ability to accelerate in my Electronic Lead Screw
project.
A friend and I were discussing bringing a 300 pound flywheel up to speed.
Vz=0 RPM, Vf=50 RPM. Reduction drive to the flywheel shaft is 32:1 so final
speed of motor is 1600 RPM.
Assume we're happy with 5 seconds to accelerate for Tz to Tf. Motor voltage is 12V.
We have the mass, we have the velocity, we have the time and motor voltage. The question is what are the calculations to determine how much current the motor will require to create this acceleration? Assuming of course the motor is 100% efficient.
We're getting all confused with F=ma and 1/2*a*t^2 etc.
What size motor is actually needed to do this?
Thanks.
John
That John, is going to be determined by where that weight is.
If 270 lbs of it is in a rim 4 feet in diameter and the other 30
is in the spokes supporting that rim, its going to take a lot
more torque to get it up to speed in 5 seconds than it would
take if its only 2 feet in diameter, its the linear speed of the
outer diameters major mass that has to be moved to twice
as many feet per second needing 4x the torque to do it for
the 4 foot example, and Einstiens E=m*v*v comes into the
picture, cuz v=2*2 is 4, but v=4*4 is 16, not 8.
That's as close as I can get to the math, sorry. I'd have to
ask someone else for a SWAG or more knowledgeable
answer too. This is a case also, of doing a bit of cheating
with a bigger vfd running at a higher voltage and the low
speed current boost could, if enough line voltage is present,
bang a 1 horse motor hard enough to natch a 3 or 4 horse
motor, knowing the overdrive will only last a few seconds.
But, if going to machine cut with that motor, I'd have an
amprobe or equ watching the motor currant to make sure
the steady load is within the FLA on the motors nameplate.
I hope the real answer means you've a motor and vfd in
stock that will do it.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
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