OHM’S LAW FOR HYBRIDS: BER or regenerative braking is a direct way of recovering AND reusing brake energy normally wasted in heating the brake linings. The law simply states the motor must be sized upon braking requirement and acceleration desires. To make the greatest use of recovering the energy upon braking, the motor battery combination ALONE must be able to provide the acceleration.
MEETING THE GOVERNMENT FUTURE REQUIREMENTS---HOW?Jul 29, 2011 President Barack Obama delivered remarks on fuel efficiency standards for 2017-2025 model year cars and light-duty trucks during an event at the White House with the pontificating announcement of 54.4mpg composite(?). The puzzling thing is it didn’t really clarify anything. In particular it puts NO emphasis in improving LOCAL driving mileage-----apparently in the grand scheme it is insignificant in the government’s mind. SO no help can be expected in the development of an affordable SUV/VAN capable of 20—25 mpg for general urban usage. TOO bad! SUVs and VANs are the most popular vehicles with young families and 80% of the driving is LOCAL.
2-MOTOR COSTS: The PAICE patents that are used by Toyota, Nissan, Ford and GMC, combine an ICE with 2 motors and a planetary gear to provide a CVT (Continuously Variable Transmission). Unfortunately for optimum advantage the two motors are NOT identical; also experience has shown that this design does not scale easily. Net result that about 15%-25% is added to the manufacturing costs compared to conventional drives.
REDUCTION OF COSTS: The Electric Only could and should cost less than a conventional car and WILL when the “economy of scale” takes place. For the gasoline hybrid it will cost somewhat more because of additional parts to perform it mission.
4-TYPES OF MOTORS: The four types of motors that can be used in Ecars and Hybrids are the VFSM (Variable Field Synchronous Motor), the PMSM (Permanent Magnet Synchronous Motor), the (SyRM) Synchronous Reluctance motor, and the Induction motor. The PMSM is now the most widely used partly because it is easier to integrate into BER. But the reservation is that the magnet material is Neodymium and the main source for this is China. This has caused renewed interest in the Induction type motor that has been successfully used in the Tesla and original GM EV1. The induction motor is a bit more difficult to work into efficient BER. The very recent interest in the synchronous reluctance motor is that it is more efficient compared to straight Induction motor and a bit easier to work into BER. Three of the motor types, the Induction, the VFSM, and (SyRM) synchronous reluctance need NO rare earth magnets in there construction and hence are less costly.
NOTE---Both Induction, and (SyRM) synchronous reluctance type motors use the same field winding arrangement and to generate Back emf the field winding have to be excited with the proper excitation. See below.
AN ASIDE: When I attended college, in my Junior year I took classes in AC/DC Machinery and as part of that had a Machinery Lab. Part of the lab set up was a variable speed DC drive motor shaft connected to an Induction motor and a Synchronous motor. All of these motors were rated at 7500 watts or 10hp nominal. Power to the lab was 120Vdc and 120/208 60 Hz Vac. Power to the testing position was brought through a single wattmeter for the DC and through 3-wattmeter’s to measure the 3-phase power. Both the AC motors were 4-pole so that the synchronous speed was 1800 rpm.
A first test was to bring the shaft speed to 1800 rpm via the DC motor and verify that there was NO voltage on the 3-phase terminals of the Induction motor. On the Synchronous motor, with the DC field current at 0amps only a very low voltage due to residual field magnetism present.
A second test was to raise the field current on the Synchronous motor and measure the winding 3-phase voltage. This is a direct measure of the Bemf (Back emf) at 1800 rpm. A 3-lamp synch tester (240 volt,15 watt test lamps) allowed (with all three bulbs out) to connect Synchronous motor to the 3-phace source. Now by varying the field current, via the 3-phase wattmeter connection you could steer power into and out of the Synchronous motor from the 3-phase power source i.e. the Synchronous motor could be a generator OR a load depending upon the field current setting.
A third test was to drive the Induction motor at 1800rpm, apply the 3-phase 120/208 Vac and note that the 3-phase wattmeter reading is at a low value. Then via the DC motor drive, the rpm is varied both above and below 1800rpm and the wattmeter readings noted. The 3-phase AC power increases as the 1800 is increased BUT most interestingly the 3-phase AC power goes negative i.e. the Induction motor is now an Induction generator. If the 1800rpm is reduced the Induction motor acts as a load and delivers shaft power to the DC motor/generator.
From the ASIDE above it is apparent that with a shaft position sensor AND a VVVF (variable voltage, variable frequency) source, all 4-types can be used to power the electric side of a hybrid OR Electric only car, so competition can help in the selection process.
SO WHERE ARE WE GOING? Because of the inherently more complex machinery, the 2-motor schemes as hybrids do cost more. Now through skillful marketing (there is NO non-hybrid version to compare to) the Toyota PRIUS is the most successful hybrid but still only amounts to less than a fraction of a percent for the total vehicle population.
The Electric only car is inherently lower cost than a conventional car although at the present time you couldn’t tell that from the offering prices. Hopefully “economy of scale” will change this. Hyundai, Ford, Toyota, Nissan, GM and Chrysler are either offering them or will be within the next 2-3 years-----------INTERESTING.