AIUI, this depends on the driving system. If the control is "V/Hz mode", then the controller is essentially "dumb". This leads to the "slip" (as described in the next point), which leads to less available torque at low end, as the motor is constantly trying to move the power faster than the rotor.
- low end torque (as in below 1/3 of the motors nominal RPM rating) is poor.
If the controller is using "V/Hz mode", then it doesn't know/care where the rotor is, it keeps the voltage static, and varies the frequency to the requested value, which leads to slip and torque loss when the rotor isn't as fast.
- the rotor phase must slip behind the voltage curve to generate torque, the result is a degraded power factor resulting in systemic inefficiencies.
If the controller is using "Vector Modulation mode" or "Direct Torque Control", then it knows where the rotor is (Either through measuring power on the phases, or by a position sensor). This way it can provide the exact power and frequency needed to move the motor, meaning there is no slip, no loss of torque, and no degradation of power factor.
Very true. It's problematic if you're building your own controller from scratch, but if you're buying a controller ready-made, this isn't really much of an issue.
- DSP type solutions required for motor control.
You might want to check that math. I get a final drive speed at the wheel of 2000RPM, which leads to a top speed of ((2000 * 2.136) / (60 * 1000)) = 256Km/h (159MPH)Economics aside, imagine an A4 chassis with one of the 47.6 Kw MSS142F-0700 powering each wheel at a 5 to 1 ratio. The site is wrong in that Max RPM is 10K rather then 28K, FYI.
With 225/55 R17's (84 inches circumference), that means at nominal RPM (7K) the car would cruise at a cool 111 MPG with 255 HP and 958 ft of torque.
Well, you could put a buck/boost converter in front of the controller, which will give you adjustably higher voltage. This isn't typically a part of most inverters, though, which could lead to further issues, including increased complexity.On a side note, the nominal specifications are at 540V DC on the inverter bus. The motors are rated to 750V max... The is running such high voltage a serious problem, even in a well designed EV solution? The motors rated current at 7K is 68 x 4 Amps and the system need some multiple, n, of 45 12V cells to obtain 540V. The question then becomes how many sets of 45 cells to wire in parallel. I clearly need to examine the power source requirements for this solution _way_ more thoroughly.