Wound motor torque formula

I need to replace 3 phase wound motor (with reostat) with a squirel-cage motor feed via inverter.
Got to choose a motor capable to start moving the load (high inertia load).

How to determide the actual torque needed to start moving the load?

Determine the torque to accelerate a mass in a given time..
This is dealing with inertia by using torque to get acceleration.

First determine the moment of inertia, which depends on the shape. For a cylindrical solid flywheel:

Moment of inertia...
I_flywheel = (m x r^2) / 2
Where:
I is the moment of inertia in kg.m.m
m is the mass in kg
r is the radius in m.
Look up moment of inertia for formulae for other shapes.
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Determine the angular velocity of the flywheel in radians per second.
Omega = (2 x pi x RPM) / 60
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For interest...
Rotational Energy in flywheel (in Joules)...
E = (I x Omega^2) / 2
In KWh...
= (J/3600)/1000
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Getting the motor to accelerate the flywheel...
The torque that can be sustained continuously over time is according to the torque (or power)of the motor at full speed. As the flywheel accelerates over a long period of time, it can be a combination of this "continuously rated torque" and a short period at "pull-up torque" say 10 seconds at 3 x rated torque. More torque can be obtained over a limited time according to the motor class. Look up the characteristic curves for your motor. Safest and simplest is to stick with "full speed torque". This can be set as the rated current or rated torque using a variable frequency drive (VFD).
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Determining the rated motor torque from power and speed...
Motor torque...
Power_KW = (torque_N.m x 2pi x RPM) / 60000
Transposing..
torque_N.m = (60000 x Power_KW) / (2pi x RPM)
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