65 Electrical Machines for Hybrid Vehicles

The motors and alternators used in hybrid electric vehicles are in principle no different from those described above. Indeed in many cases there is no significant difference between the motors used in hybrid vehicles than any other type.

The basic principles of some types of hybrid vehicle were described in Chapter 1. In the series hybrid vehicle there is really nothing different about the electrical machines from those used in a host of other applications. The traction motor, for example, will work in the same way as in the case of the classic battery powered electric vehicle.

It is in the parallel hybrid that there is scope for some novelty in machine design. One example is the crankshaft mounted electrical machine that is used in a number of designs, including the groundbreaking Honda Insight. Here the electrical machine, which can work as either a motor or generator, is mounted directly in line with the engine crankcase. Such machines are in most cases a type of brushless DC (or synchronous AC) motor, as described in Section 6.3.2. They will be multiple-pole machines, since their location means their dimensions need to be short in length and wide in diameter. They are nearly always different from the machine of Figure 6.25 in one important respect: they are usually 'turned inside out', with the stationary coils being on the inside, and the rotor being a band of magnets moving outside the coil. The idea is shown in Figure 6.35. The larger diameter permits this construction, which has the advantage that the centrifugal force on the magnets tends to make them stay in place, rather than throw them out of their mounting.

It is worth pointing out that this same type of inside out motor is used in motors that are integral with wheels, such as the machine of Figure 8.9.

However, not all parallel hybrids use special multiple motors of this type. Some hybrid vehicles the electrical machine use a fairly conventional, single pole, fairly high speed machine, which is connected to the engine crankshaft much like the alternator in an ordinary conventional IC engine vehicle. The fan belt type connection is made rather more robust.

Permanent magnets are an integral part of the rotor, which is on the OUTSIDE.

Air gap

Air gap

Another type of parallel hybrid where fairly conventional motors are used is the type where the front wheels are driven by an electric motor, and the rear are driven directly from the IC engine. The front wheels are electrically powered when more power is needed, or when driving very slowly in a queue, or when four wheel drive is required for traction purposes. Similarly, braking is provided by the front axle, using the machine as a generator, regenerating some of the energy when slowing down. This type of parallel hybrid may well be suitable for some larger cars and vans, and is illustrated in Figures 1.12 and 1.13.

Figure 6.36 Demonstration hybrid diesel/electric power unit installed in a Smart. The motor/ generator is the unit marked 'hyper' at the base. (Photograph reproduced by kind permission of Micro Compact Car smart GmbH.)

The machine driving, and being driven by, the front axle need not be any different from those described in Section 6.3.

Yet another parallel hybrid arrangement that has been tried with some success on the Smart car is shown in Figure 6.36. Here the main engine was left almost unaltered, but a motor was added near the base of the engine, so that it connects to the drive differential via its own drive system. This allows it to drive the vehicle if the engine is not working, yet it does not have to be in line with the crankshaft. Minimal alterations are made to the rest of the engine, which reduces cost. The shape and working speeds of the electric motor mean that it does not need to be of a very special type.

Hybrid Cars The Whole Truth Revealed

Hybrid Cars The Whole Truth Revealed

Hybrid Cars! Man! Is that a HOT topic right now! There are some good reasons why hybrids are so hot. If you’ve pulled your present car or SUV or truck up next to a gas pumpand inserted the nozzle, you know exactly what I mean! I written this book to give you some basic information on some things<br />you may have been wondering about.

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