gearmotor max torque

[GrizzlyRancher]

We're using a 15-hp gearmotor (3-phase, 1730 rpm, 460 V, ratio = 165) on an auto-depalletizer machine. I need to find out the maximum torque produced by this motor at startup, in order to calculate the maximum shear loading on a lock pin. I've looked for start-up torque equations and tables but have come up empty-handed so far. I have no way of finding the circuitry of this particular motor, as we cannot conduct locked-rotor or similar tests (we're in full production). Does anyone know of equations, tables, resources where I can find the maximum torque of this motor? Any help would be greatly appreciated.

Thanks!

 

[ozmosis]

GrizzlyRancher
The basic calcualtion for nominal torque will be:
T=(Hp x 5250)/motor speed
in your case, T= 15 x 5250/ 1730 = 45.52Lb-Ft
Then you multiply by your gear ratio =7511Lb-Ft
A typical maximum torque rating on startup would be 150%
so this gives about 11,266Lb-Ft.
This is theoretical torque exluding the effects of efficiency loss and also the maximum torque rating of your gearbox.
You may need to advise the type of gearbox to determine the eff loss.

 

[ozmosis]

I ought to add that the starting torque I mention of 150% is a typical NEMA B motor. Other types will typically have a higher starting torque (NEMA C, D will be 220~280%)

 

[GrizzlyRancher]

Thanks very much for the quick response - it's exactly what I needed!