I recently tried to measure current draw for certain torque values for the VEX 393, and was hoping you could help with a question or two? We connected the 393 to a winch set up and lifted a series of increasing weights. The motor was hooked to a DC power supply and the voltage was set to 7.2-Volts. As each weight was raised by the winch, we were able to record the RPM’s and the current draw. My first question is whether we made a mistake by setting the voltage to remain at 7.2-Volts? It seems like other experiments I’ve seen had the voltage varying as torque changed?
Also, we could not get past about 0.8-Nm of torque. This drew 2.4-amps and we only had the winch spinning at 19-RPM. It just seems like the motor is not as powerful as we expected. We took many measurements from 0.0-Nm to 0.8-Nm of torque. When we plotted the trendlines for torque vs. current & torque vs. speed, we are not getting the same trends/slopes as the published values.
Torque Speed and Power - VEX 393 Measured.pdf (1.61 MB)