load inertia is greater than NEMA MG 1
load inertia is greater than NEMA MG 1
(OP)
Hi,
I am working with a spec that states "Load inertia within NEMA MG 1 (when load inertia is greater than NEMA MG 1, use API STD 541 motor)." I've looks through NEMA MG 1, and I'm having trouble understanding exactly what to look for. I've calculated that my Load Inertia is 246.03 lb-ft² for a particular 300HP 3600rpm motor, but do not know if that is considered greater than NEMA MG 1. Would someone please explain?
Thank you!
Ian
I am working with a spec that states "Load inertia within NEMA MG 1 (when load inertia is greater than NEMA MG 1, use API STD 541 motor)." I've looks through NEMA MG 1, and I'm having trouble understanding exactly what to look for. I've calculated that my Load Inertia is 246.03 lb-ft² for a particular 300HP 3600rpm motor, but do not know if that is considered greater than NEMA MG 1. Would someone please explain?
Thank you!
Ian





RE: load inertia is greater than NEMA MG 1
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: load inertia is greater than NEMA MG 1
I find it s tad suspicious that your calculated load inertia is exactly what is permitted by NEMA MG-1 (Table 12-7). Is this a coincidence.?
GG
"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)
RE: load inertia is greater than NEMA MG 1
THanks!
RE: load inertia is greater than NEMA MG 1
But here's the process:
WK2 = W (weight in lbs.) x K2 (radius of gyration)2 = lb. ft.2 (moment of inertia)
W = weight of the load in pounds
K2 (radius of gyration) = (radius of disc. in feet)2 / 2
But if you have gears and such, you have to determine the total WK2 for each one. Same for any belt drives / sheaves.
This is why it's better to get a value from someone who knows it, because in order to size the power train components, they had to know all of this too.
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington
RE: load inertia is greater than NEMA MG 1
Do you suspect there might be an issue with your load having high inertia?
What type of load is it (ie centrifugal fan, pump, compressor, conveyor)
?Is there a gear-box in the drive train?
Do you have the option for a VF Drive, or is DOL starter the preferred option?
GG
BTW a API 541 motor is lotsa more $$ than a standard NEMA MG-1.
"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)
RE: load inertia is greater than NEMA MG 1