Can an Industrial Motor Be Modified for EV Conversion Efficiency?

[yikes]

I am planning an EV conversion and have been looking at different motor options that would be feasible to use. One possibility that i have been investigating is using a standard industrial motor. The main limitation encountered with these motors are the weight and the rated rpm and hp. On another forum there has been discussion about rewiring a standard motor for a lower voltage and then driving the motor at a higher frequency to obtain the needed rpm and hp requirements. In theory this should work, but some unanswered questions remain. What efficiency loss will be experienced as a result of this modification? Will ther be increased I2R losses? What about any other losses due to magnetic changes. What increases could be achieved with a standard 230/460v, 1800 rpm, 15 hp motor. Ideal parameters would be in the 5-6000 rpm range with a rated hp/kW rating of 40-50. I greatly appreciate any advice, help, or smacks in the face to wake me up from a possible dreamworld scenario.

 

[Chuck WI]

Induction motors run quite well above nameplate frequency an constant V/Hz providing rated torque and increased speed and horsepower. A 230/460 volt motor can be run on the 230 volt connection up to 460 volts, 120 Hz. Bearings, balance, and centrifugal force on the rotor would be issues to check. Many 1800 RPM motors can go to 3600 RPM without difficulty, but running a 3600 RPM motor at 7200 RPM would be more difficult. A TEFC motor might need a smaller fan. You should use a motor designed to run on a variable frequency drive. That may mean that the fan will be oversized to start with.

You might want to consider running an 1800 RPM motor to 120 Hz at constant V/Hz and at constant voltage, constant power, from 120 Hz to 180 Hz.

A condensed version of the NEMA motor standard is available as a free download:
http://www.nema.org/stds/mg1condensed.cfm

The NEMA Application Guide for AC Adjustable Speed Drive Systems is available as a free download:
http://www.nema.org/stds/acadjustable.cfm