Page 197 - Automotive Engineering Powertrain Chassis System and Vehicle Body

Hybrid vehicle design CHAPTER 7.1

Fig. 7.1-20 MAN/Voith concept city bus: (a) low floor package; (b) wheel motor; (c) controller; (d) drive characteristics.

transverse-flux wheel motors which drive the wheels losses. A new control process permits operation of the
through two-stage hub-reduction gearsets, (b). The motor in a field-weakening type mode, in spite of PM
diesel is rated at 127 kW and the generator at 135 kW; excitation. The generator is almost identical in concept
the controller, (c), is of the IGBT converter type and but involves no field weakening. Each has concentric
also developed by Voith. It provides a differential construction of permanent magnets, rotor/stator soft-
action to the wheel motors on cornering. Permanent- iron elements and stator winding; see below. Armature
magnet synchronous wheel motors are rated at 57 kW elements are U-shaped cut strip-wound core sections,
and have a maximum speed of 2500 rev/min; see table embedded in the ring-shaped supporting structures of
at (d). The bus is 12 metres long and has water cooling inner and outer stators. Each core surrounds the
for its generator, converters and wheel motors. As well windings and forms a stator pole with its cut surfaces
as providing virtually jerk-free acceleration, the drive facing the rotor. The latter is pot-shaped and posi-
system is seen by MAN as providing the possibility of tioned between poles of the outer and inner stators. In
four-wheel drive on future articulated buses to im- the stator pole region it comprises magnet and soft-
prove traction and stability in slippery road conditions. iron element while in the winding region a ring of GRP
The term transverse flux motor refers to the means serves as the connecting element. The inverters supply
used to guide the magnetic flux in the stator; this is the motors with sinusoidal currents and voltages until
new to inverter-supplied PM types and involves a novel the nominal operating point is reached; operating fre-
collector configuration. Double-sided magnetic force quency is 10 kHz. In field-weakening mode the in-
generation is also new and involves a patented double duced voltage exceeds intermediate circuit voltage and
air gap construction having high idling inductances and only square wave voltages are supplied to the motor.
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force densities up to 120 kN m/m , with relatively low Power output then remains constant and the operating

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