Electrical Engineering - Moment of Inertia of a motor

Author

Moment of Inertia of a motor

Govind

2007-08-19, 3:25 am

Govind
View profile
More options Jun 24, 5:06 pm
Newsgroups: alt.engineering.electrical
From: Govind <govinda...@gmail.com>
Date: Sun, 24 Jun 2007 12:06:38 -0000
Local: Sun, Jun 24 2007 5:06 pm
Subject: GD Square of a motor
Reply | Reply to author | Forward | Print | Individual message | Show
original | Remove | Report this message | Find messages by this author
I want to know about what is the GD square ( Gyrational Torque) of
the motor. I am aware that higher kW motors for e.g 5MW motors load
torque curves are checked by overlapping with the load curves i.e, for
e.g pumps to check weather the selected motor will able to start the
load or not. in this scenario i want to know very particularly about
the meaning of GD square of the motor and a Pump and also the Wk^2
(Moment of inertia J ) of the motor / load ----- Finally how i have to
cross check the values with motor and with load.

How those values are calculated - can anyone suggest a formula to
arrive those values for a motor please.

dave y.

2007-08-19, 5:25 pm

On Sun, 19 Aug 2007 08:03:54 -0000, Govind <govindarul@gmail.com>
wrote:

>
>
>Govind
>View profile
> More options Jun 24, 5:06 pm
>Newsgroups: alt.engineering.electrical
>From: Govind <govinda...@gmail.com>
>Date: Sun, 24 Jun 2007 12:06:38 -0000
>Local: Sun, Jun 24 2007 5:06 pm
>Subject: GD Square of a motor
>Reply | Reply to author | Forward | Print | Individual message | Show
>original | Remove | Report this message | Find messages by this author
>I want to know about what is the GD square ( Gyrational Torque) of
>the motor. I am aware that higher kW motors for e.g 5MW motors load
>torque curves are checked by overlapping with the load curves i.e, for
>e.g pumps to check weather the selected motor will able to start the
>load or not. in this scenario i want to know very particularly about
>the meaning of GD square of the motor and a Pump and also the Wk^2
>(Moment of inertia J ) of the motor / load ----- Finally how i have to
>cross check the values with motor and with load.
>
>How those values are calculated - can anyone suggest a formula to
>arrive those values for a motor please.

So what exactly is 'Gyrational Torque' or GD squared? Sounds like
some nonsense you made up just to troll. Or maybe you got it from
some other troll. If you'r serious, and since you throw in Wk^2,
maybe you're getting the idea of inertia mixed up somehow?

daestrom

2007-08-23, 5:25 pm

"Govind" <govindarul@gmail.com> wrote in message
news:1187510634.584224.308600@x35g2000prf.googlegroups.com...
>
>
> Govind
> View profile
> More options Jun 24, 5:06 pm
> Newsgroups: alt.engineering.electrical
> From: Govind <govinda...@gmail.com>
> Date: Sun, 24 Jun 2007 12:06:38 -0000
> Local: Sun, Jun 24 2007 5:06 pm
> Subject: GD Square of a motor
> Reply | Reply to author | Forward | Print | Individual message | Show
> original | Remove | Report this message | Find messages by this author
> I want to know about what is the GD square ( Gyrational Torque) of
> the motor. I am aware that higher kW motors for e.g 5MW motors load
> torque curves are checked by overlapping with the load curves i.e, for
> e.g pumps to check weather the selected motor will able to start the
> load or not. in this scenario i want to know very particularly about
> the meaning of GD square of the motor and a Pump and also the Wk^2
> (Moment of inertia J ) of the motor / load ----- Finally how i have to
> cross check the values with motor and with load.
>
> How those values are calculated - can anyone suggest a formula to
> arrive those values for a motor please.
>

A good applied physics text will explain the concept. Think of 'moment of
inertia' as the rotational equivalent of simple inertia.

For a pair of masses suspended on a cross-arm with the pivot point in the
middle, the moment of inertia is the sum of mass times distance from pivot
squared. (used to use 'weight times k^2' hence Wk^2). For more complex
shapes such as cylinders and disks, there are various formula derived from
calculous. A simple uniform cyclinder spinning along its axis is 1/2wd^2.

For large motors with fans, spider-web iron with holes passing through the
length of the iron punchings it can be quite a bit more complext a
calculation. But basically find the moment of inertia for each individual
component relative to the shaft (don't forget the shaft itself) and sum them
up. If driving a load through gearing, one must account for the gear ratio
as well.

daestrom

LinkBot