retrofitting electric motor 1

[AT1000]

Hope someone out there can point me in the right direction.
At the moment there is an old ac variable speed motor (with the moving brush gear to vary the speed)It needs to be updated to 3ph squirrel cage motor with an inverter. variable speed motor is 33 h.p. 25oo r.p.m. at top speed. Need to replace with 2 pole motor. Problem is no information is available for the torque requirements. How can you be sure new motor will be ok.
thanks
at1000

 

[electricuwe]

Calculate the torque available from the old motor:

torque(old) = power(old)/rotational speed(old)

power(new) = torque(old)*synchronous nominal rotational speed(new)

This will lead to a slightly higher power rating of the motor and the inverter.

Maybe there were some kinds of variable speed AC-motors providing more torque at lower than nominal speed (like a DC motor with series connected field). In this case you have to be careful ! I will check if such motors have been used in the past.

What type of load is the motor driving ?