Can a smaller ev with ac motor be powered by an ac gen instead of using a battery pack and everything that would go along with it? If so, what would the arrangement be going from gen to motor?


closed as too broad by Elliot Alderson, Charles Cowie, Voltage Spike, RoyC, mkeith Apr 9 at 3:05

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  • \$\begingroup\$ Probably. the "arrangement" as you put it would consist of a VFD. Why do you want this? \$\endgroup\$ – Hearth Apr 6 at 22:49
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    \$\begingroup\$ Are you describing a hybrid with an engine driving a generator which powers the motor? The AC generator power would need to be rectified to DC the inverted back to variable frequency AC to provide speed control. That arrangement is called a variable frequency drive (VFD), \$\endgroup\$ – Charles Cowie Apr 6 at 23:32

Gas vehicles with electric motors do exist in various forms. What you're asking could easily be done, but an "AC generator" involves unnecessary energy conversions. Every time you convert energy, you lose some, so an "AC generator" of the type you are referring is a gas engine attached to an alternator, with field coil compensation and throttle regulation. You're proposing to attach this arrangement to an electric motor/motor set to run the car. The electric motor/ motor set requires some form of drive, which means an additional power conversion, unless all electric motors are running at the same power level and the field and throttle compensation are dedicated to providing the correct drive voltage/current for the electric motors.

For a given gas motor size, if you have no ability to store significant power (battery bank), your input cost versus output power will be higher if the gas motor directly provides driveshaft torque. The only loss the electric system would be eliminating would be drive system friction, and it is adding in line loss, power conversion loss, etc.

To make an arrangement involving both gas and electric useful, usually some other feature of the combination must be utilized, such as:

  • Using regenerative braking(treating wheels as generators when slowing down), which works best at higher speeds, so must be accompanied by a traditional break for full stop. Recovered energy is significant, especially in stop and go traffic where gas losses per acceleration add up quickly.
  • Eliminating drive train friction by using wheel motors rather than a single electric motor on a physical differential, you save the energy and maintenance cost that would go into friction of drive train and cost to manufacture it at the cost of having to engineer and manufacture 4 state of the art, finely machined electric motors instead of a single large gas motor which is significantly easier to manufacture due to existing production methods.
  • With the right set of sensors, responsiveness of the vehicle can be extremely high compared to a gas vehicle, and there is arguably a significant safety benefit from having your vehicle respond more precisely and rapidly. An extremely large effort goes into engineering a system that takes advantage of this, as the processor(s) controlling the system must respond very rapidly and intelligently, allowing motors to operate close to their limit or within an optimal efficiency band, compensate for differential in an intelligent way, respond within thermal and electrical limits of every component of the system. This method can do things that a traditional differential cannot if done well, like actively measure countertorque and speed on each wheel in real time and minimise slip, giving you an extremely intelligent 4 wheel drive operation.
  • Hybrid vehicles can in theory have some of these benefits without strictly requiring you live somewhere where charging stations are common or have resources like multiple vehicles for specific purposes. I'm not informed on the current hybrid vehicle market, but to make an electric vehicle that is better to run than a gas vehicle, you'll have to put in a lot of effort and money.

All of that said, the "arrangement going from generator to motor", you may have to infer from the above. You can absolutely make it work, but it may take some effort to figure out how to make it worthwhile, especially without a battery in the system. Adding a small efficient generator and rectifier to your electric golf cart would be much more plausible than to your hoverboard or bicycle, and working with an already complex vehicle type will require tremendous effort.


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