data plate directly or calculate it from the RPM stated on the data plate or you can count the coils and divide by 3 (poles per phase) or by 6 (pairs of poles per phase). Where the power of the induction motor is constant, the torque increases at the rate that the speed decreases....
There are most commonly three types of ECMs: constant cubic feet per minute, constant revolutions per minute and constant torque. For HVAC applications, it’s the controls built into the ECM that determine its type. The motor is the same. These aren’t the only types of ECMs in the world...