Submitted by Anonymous (not verified) on Sun, 11/04/2012 - 08:23
This week marks the first step in getting real performance out of our second generation machine.
The EMRAX motor was successful setup to be controlled by the Tritium Wavesculptor200 controller that we will be using. This controller was used on our first machine were It operated very reliably. On that machine it was mated to Remy HVH250 motor which is an Internal Permanent Magnet (IPM) machine. Tritium had to do the setup because this machine does not have a constant torque to current relationship because the there are two torque generating components in the machine. One is due to the permanent magnets and the other is due to the reluctance of the iron core. Each interacts a bit differently with the flux generated by the current through stator windings. All and all it’s a much more complicated, but advanced machine. However for our needs, an electric motorcycle, we believe it was too much motor.
The EMRAX on the other hand is a Surface Mount Permanent Magnet (SMPM) machine meaning a relatively constant torque to current relationship exists. This makes tuning and controlling from the Tritium a lot easier. Additionally the EMRAX is an dual rotor axial flux outrunner electric machine. Both an axial flux and outrunner machines have an inherently high torque to current ratio. With the addition of a halbach array magnet arrangement, which concentrates the magnet flux within the motor and eliminates the need for backing iron on the rotor, a very lightweight, high torque machine is created. This is an ideal motor for an electric motorcycle. Compared to the Remy the EMRAX is 75% lighter and 60% smaller while still delivering the same power levels. Note if a larger controller was used and higher power was available the Remy would begin to outclass the EMRAX.
The EMRAX’s temperature sensor and speed/position sensor were easily adapted to the Tritium interface. A few harnesses were reversed which lead to the some extra troubleshooting. About 8 hours were spent to get the initial setup working, but about 5 were user setup error. Setup with a SMPM on the Tritium is quite simple. One feature has you spin the motor by hand so that the controller can monitor the waveform of each phase in relation to the signal from the speed sensor. The next feature drives 20A through 1 phase and measure the resistance and inductance of the phase. The controller then builds a virtual model of the machine and theoretically has full control of the machine. On the 45V bus used for this setup we were able to get the EMRAX to ~450RPM. Higher no load speed tests will be run (up to hopefully 4500RPM) and then full load (higher torque) tests will be performed on an engine dynamometer. More to come…