Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 39)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 39
Drive Configuration Chapter 1
we have a formula that isolates the connected inertia.
For the variables, Tacc is the 100% rating of the drive in lb•ft. Let’s say I’m using a
10 Hp drive with a 10 Hp motor. We can rearrange the Horsepower formula
below to solve for torque in lb•ft.
My motor is 10hp, 1785RPM,
and rearranging it to
So let’s plug in the numbers. T = lb•ft
And (t) comes from what the drive reports as seconds of inertia after running the
inertia tune. Let’s say that the drive reported 2.12 seconds of inertia. And now
organizing the variables we have
Tacc = 29.42
(t) = 2.12
N = 1785
plugging these into the formula, WK
2
= 10.76
After these calculations, one can conclude that the connected inertia is equal to
10.76 lb•ft
2
. Multiplying by 0.04214011 you get 0.453 kg•m
2
.
What effect can P71 [Autotune Torque] have on these calculations? Regardless
of the value entered here, the drive interpolates as if this value was 100%. So the
seconds of inertia reported by the drive always reflects 100% torque.
CEMF Test
This is a Rotate test used to measure a PM motors CEMF.
Autotune Parameters Information about some other Autotune Parameters not
covered above.
HP
T Speed
×
5252
------------------------- =
T
HP 5252
×
Speed
----------------------- =
T
10 5252
×
1785
-------------------- =
WK 2
Tacc 308
×
t
( ) ×
ΔN
-------------------------------------- =