# Datasheet help!

Discussion in 'General Electronics Chat' started by mereldawu, Aug 5, 2013.

1. ### mereldawu Thread Starter New Member

Aug 5, 2013
2
0
Hi,

I have a 2.2kW squirrel-cage induction motor which comes with a datasheet as attached, the machine I'm looking at is highlighted in green.

I need to know the rotor inertia, but there's a bracket that says X.01 after the normal kg.m^2. What does this mean??

I've checked the datasheet of some other induction machines with the same power rating, and it's at 0.089 kg.m^2, which is over 15 times more.

I've got all the equivalent circuit parameters and I tried to reverse-engineer the DOL starting torque and current, and I get about 0.03 kg.m^2 as the inertia.

p.s. I know I could always just calculate the inertia from the motor decelerating curve, but with the equipment I have it's not the easiest thing to do

Any help is much appreciated, thanks in advance!!

Regards,

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2. ### #12 Expert

Nov 30, 2010
16,704
7,354
For local denizens: Click the drawing to get it to open in a new tab. Go there, right click, save as, open it in a media viewer, then rotate counterclockwise to read the chart.

Can't help further than that. You're over my head.

3. ### crutschow Expert

Mar 14, 2008
13,505
3,378
Offhand I would think the X.01 means you divide the value shown by 100 to get the correct value. But that would give a value of 0.55 kg.m^2 which seems rather large compared to the other typical values you show.

4. ### #12 Expert

Nov 30, 2010
16,704
7,354
That's what I came up with. About 7 times as large as it should be, but I do not have the expertise to back up this claim.

5. ### wayneh Expert

Sep 9, 2010
12,391
3,246
Having written many data sheets myself, I certainly would not rule out an error. They persist until someone points them out. I've had some errors go years. You just hope it's not a critical customer that finds it, but it usually is.

6. ### mereldawu Thread Starter New Member

Aug 5, 2013
2
0
Thanks everyone!
I'll just have to experimentally verify it then.
I guess it's good practice anyway