Electronic – Motor Induction motor design specifics

50 RPM suggests that the motor is actually a gear motor. So the rated speed of the gearmotor is 50 RPM, the rated torque is 15 in-lbs and the rated current is 0.9 A. As a sanity check, 50 RPM at 15 in-lbs gives you an output power of ~8.9 W. The input power is 24 V * 0.9 A = 21.6 W. That gives an efficiency of 41.2% at the rated load, which is not unreasonable for a gearmotor of that size.

Motor regulation is a figure of merit for DC motors. It can be thought of in a number of different ways. Some people like to think of it as the slope of the speed torque curve. What it tells you is the motor's ability to turn electrical power into mechanical power. It can be calculated by \$\frac{R}{k_t^2}\$, where \$R\$ is the terminal resistance of the motor and \$k_t\$ is the torque constant of the motor. A lower value indicates better heat conversion.

Some people also use a similar figure of merit called the motor constant (\$K_m\$). \$K_m = \frac{k_t}{\sqrt{R}}\$. As you can see, this is just the reciprocal of the square root of the motor regulation that I talked about in the previous paragraph.

In the last 25 years there has been an enormous amount of evolution and technology that has gone into controlling 3 phase Variable Frequency Drives. Discussing any details around how to do it in a new method or better exceeds the scope of a forum such as this, but would be a good basis for a PHD thesis.

A good starting point in your study is Vector mode control, which is typically one of 3 standards modes to run an off the shelf VFD drive in.

Constant Torque is a standard mode in most VFDs - BUT if you are talking a 50 or 60 hz motor - why would you choose to run at 100 hz UNLESS you had a reduction in torque requirement in your 60 hz - 100 hz range. In my experience every 3 phase motor rated at a base speed of 60 hz has a reduction in torque capability for speeds above 60 hz.

You will also want to do some reading and study the Pull up torque curve which has been a staple in motor theory and motor manuals for 75 years. If you get a good grasp for how Vector control modes manipulate this Torque curve at various speeds - you will have a foundation to start with.