Use a Multi-Phase AC induction motor instead of a 3 Phase AC motor
My suggestion for GM is to use a Multi-Phase AC induction motor instead of a 3 Phase AC motor
Although five years ago it would not have been possible to have a practical Multi-Phase AC Induction Motor, this technology which is being certified for aerospace use to drive huge airplanes on the ground, would tailor perfectly for the Volt and significantly reduce its engineering complexity, save weight, and REDUCE COSTS for producing the vehicle.
There are two issues here: 1. Is there a multi-phase AC induction motor? (And what is it called?)
It is called the Chorus® Meshcon™ Motor, and is a high-phase-order motor/drive system that offers ten times the startup or acceleration torque of a conventional motor and drive of the same rated horsepower and base speed
2. Why is it a better motor for use in the Volt?
1) 10x “Burst” Torque for quick acceleration.
2) Low Speed – High Torque operation: (Less Complex Power Train via a “Virtual Transmission”)
1) 10x “Burst” Torque for quick acceleration.
Think of this Burst Torque as the ‘oomph’ needed to go from a complete stop to get onto the highway. At present, having chosen a 3-Phase AC electric motor which has less power density than a Permanent Magnet motor, the motor and electronics are oversized to meet the “burst” torque requirements. Chorus Meshcon can provide the same performance (or better performance) in a smaller, lighter, AND less expensive package. It represents a performance gain while reducing costs.
REDUCED COSTS achieved by savings in:
* Electronics (smaller and cheaper)
"But wait! Doesn’t this need more batteries to provide the increased current?"
Actually no, as a Capacitor (or “UltraCapacitor”) can provide that 10-15 seconds of greatly increased current that is needed for this “Burst” torque.
Therefore there is no ‘trade-off.’ You get a smaller and lighter electric motor that provides MORE Torque but does not require more of the expensive and heavier batteries. It is possible that the use of a capacitor would mean that the total number of batteries could be reduced since the peak draw from the batteries can reduced with a supplemental Capacitor or UltraCapacitor. This means that the decision on the size and types of batteries will be limited to only their storage requirement and this should also REDUCE COSTS.
2) Low Speed – High Torque operation: (Less Complex Power Train via A “Virtual Transmission”)
Chorus Meshcon provides a ‘virtual transmission’ between “high speed operation” and low speed ‘high-torque’ operation that simplifies power train engineering complexity by reducing the gearing needed to get higher torque from the motors at low speeds. COSTS ARE REDUCED by simplifying the engineering of the power train, and more weight is removed from the vehicle.
Chorus Meshcon specifically utilizes harmonic drive to "spoof" the drive electronics to think they are operating at a higher speed to get the low speed high torque performance. This greatly expands the amount of overload torque the motor can provide, which adds the following benefit: The Alternator and Starter for the Volt can be a single motor instead of two separate motors.
Most vehicles have Alternator and Starter as separate devices because of cost. Until Chorus Meshcon came along, it wasn’t cost effective to replace both motors with a single motor that was smaller and lighter than each of the two motors individually.
The company which developed this new type of motor is pursuing FAA certification and developing it for use on Delta Airlines fleet of 737NGs and has evaluated it for use in Hybrid Vehicles. They have determined that the best Hybrid Vehicle for it to be used in, where the benefits in terms of Costs and Performance are the greatist are Series Hybrids and the Volt is a Series Hybrid! Information about this analysis of its use in Hybrid Vehicles can be found at www.ChorusCars.com
And that wraps up my suggestion for GM regarding the Volt.
While I don't know if the Chorus Meshcon motor would otherwise be well-suited to the Volt, I doubt that GM is considering using a separate starter and generator on the Volt's ICE. That would add weight and complexity, and they'll already have to have a big generator coupled to the engine via some connection that will transmit more torque than is required to start the engine. I think even their BAS semi-hybrids use the motor/generator as a starter, though I may be wrong about that.
"Use a Multi-Phase AC induciton motor instead of a 3 Phase AC (induction) motor"
Not sure how many more phases then 3 are implied by "Multi" but here is a quick abstract from Science Direct:
Due to the potential benefits resulting from the use of a phase order higher than three in transmission, some interest has also grown in the area of multi-phase machine. For machine drive applications, multi-phase system could potentially meet the demand for high power electric drive systems, which are both rugged and energy-efficient. High phase number drives possess several advantages over conventional three-phase drives such as: reducing the amplitude and increasing the frequency of torque pulsation, reducing the rotor harmonic currents, reducing the current per phase without increasing the voltage per phase, lowering the dc link current harmonics, higher reliability and increased power in the same frame. The high phase order drive is likely to remain limited to specialized applications where high reliability is demanded such as electric/hybrid vehicles, aerospace applications, ship propulsion, and high power application where a combination of several solid state devices form one leg of the drive. The research has been underway for the last two decades to investigate the various issues related to the use of multi-phase machine as a potential alternative to the conventional three-phase machine. This paper, therefore, reviews the progress made in multi-phase induction machine drive research and development since its inception. Attempts are made to highlight the current and future issues involved for the development of multi-phase induction machine drive technology for future application.
The statement that multi-phase is cheaper is just propaganda. Adding complexity adds cost. Yes I know the argument about cheaper smaller power transistors, but this will not offset the fact that there are more of them and each has to have its own drive electronics and control. A multi-phase motor is also more complex to build. The "advantage" of more efficiency below 5mph is just not worth it, and anyone who has driven a Tesla Roadster will tell you that low-end torque is not a problem.
[QUOTE=Aaron Bianco;9995]My suggestion for GM is to use a Multi-Phase AC induction motor instead of a 3 Phase AC motor
I think the GM-Volt team should really think about the present and especially the downstream potential of the chorus meshcon motor discussed by Aaron Bianco.
Winding failure is the biggest problem (even though it is a very small failure rate) of electric motors. Research from Palo Allto U. seems to imply that steer by wire using 6 phase motors will give a failure rate that is better than using mechanical parts.
The architecture of the Chorus Meshcon Motor is well suited to be enhanced to compensate for winding failures. A number of companies are already making embedded wheel electric motors.
Significant weight savings and improvements in steering can be made by having these motors in all four wheels. The computer technology to give the requied degree of safety is well understood. (Perhaps not by the various transport departments who have a responsibility for determing car safety).
Perhaps the GM-Volt team should revue their long term electric motor technological goals and see how they align with this image of the future?